Clark GEX20-30 (RATED CAPACITY : 2000~3000kg). SERVICE MANUAL (2006)

Group 23, Brake System

Specifications

Service Brake Operation

The Service brake pedal operates a master cylinder

Service Brake:

mounted on the front frame. The master cylinder operates

Type: Wet disc brake

a wheel cylinder. The wheel cylinder operates a shoe lin-

ings to be contacted on drum.

Fluid: Hydraulic fluid, RANDO HD32 or NUTO H32

in accordance with CLARK specification MS-68

(CLARK #2776239)

Parking Brake Operation

Pedal Freeplay: None

Operate the brake by pulling the hand brake mounted on

the battery hood. The depressed pedal tensions cables

Parking Brake:

connected to a brake shoe at each brake assembly, thereby

applying the brakes.

Type: Hand brake linked to service brake at each wheel.

Press the button on the front side of hand brake, then the

Holding Test: Rated load on 15 % grade.

parking brake will be released. This handle releases the

ratchet, and a return spring returns the pedal and cable to

the off position. The ratchet also operates the parking

brake interlock switch and the parking brake indicator

light switch.

General Description

Brake pedal linkage - A mechanical system through which

Service Requirements

the brake pedal operates the master cylinder.

Operational checks and inspection of linkage, brake lin-

Master cylinder - The pistons are activated by brake pedal

ing, and brake lines are specified in the Periodic Service

movement.

Chart in Group PS.

Brake lines - These lines carry the brake flow from the

Service brake linkage adjustment and lube are not nor-

master cylinder to the wheel cylinders.

mally required.

Service brake assembly - The drums, shoes and wheel cyl-

Brakes are self-adjusting and normally require no adjust-

inders.

ment.

Parking brake-Operates the service brake shoes via cables.

A leaking master cylinder should be overhauled or

See “Parking Brake Adjustment”, in this Group for

replaced.

details.

23-1-2 • Brake System Specifications and Descriptions

SM 765, Nov ’06

Group 23, Brake System

Section 4

Brake Bleeding

Bleed brakes when:

3. Attach a clear hose to a bleed screw on one of the

brake cylinders. Place the other end of the hose in a

• The brake pedal feels spongy.

jar containing Hydraulic fluid, RANDO HD32 or

• The brake master cylinder or wheel cylinders-or

NUTO H32

lines between-have been leaking and/or have been

in accordance with CLARK specification MS-68

repaired or replaced.

(CLARK #2776239).

• Troubleshooting otherwise indicates that air has

4. Open the bleed screw.

been introduced into the system.

5. Depress the brake pedal and watch fluid flow into the

Bleed the brakes as follows:

jar. When the fluid appears to be free of bubbles,

tighten the bleed screw, then release the pedal.

1. Park truck on level floor. Put direction control in neu-

tral. Lower forks to floor, tilt forward, and apply

6. Check the fluid in the brake reservoir. Refill as

parking brake.

required.

2. Remove cap from the brake reservoir to be sure it is

7. Release the parking brake and operate the brake

full of fluid.

pedal. If the brake pedal does not come up or still

feels spongy, bleed the system again.

SM 765, Nov ’06

Brake Bleeding • 23-4-1

Group 23, Brake System

Components Disassembly

Freeplay Adjustment

Use Figures 1, 2, and 3 as guide to disassembly and

When the brake pedal linkage is properly adjusted, brak-

adjustment.

ing should begin only after the pedal is depressed a certain

distance, This is “Freeplay” is Adjusted as follows :

Components Reassembly

1. Loosen the jam nut on the rod brake master cylinder

(Figure 1).

Replace the brake pedal components as shown in Figures

1 and 2 using fastener torques where shown. Also use the

2. Depress the brake pedal 4~6mm (0.16~0.24 in).

following notes:

3. Adjust the rod until you feel the push rod make clear-

1. Clean the reservoir and master cylinder hoses and fit-

ance with the cylinder piston.

tings. Make sure no contaminants enter the braking

system.

2. Adjust pedal free play as described in “Pedal Adjust-

ment” on the page.

3. After re-assembly and adjustment, the brake system

must be bled, see Section 2 in this Group. After

bleeding, check all fluid connections for leaks and

test brakes completely before returning truck to ser-

vice.

23-5-2 • Pedal and Master Cylinder Service (Removal, Replacement, and Adjustment)

SM 765, Nov ’06

Group 23, Brake System

Section 6

Parking Brake Service

Operation

2. Actuate and release pedal six to eight times.

3. Readjust and tighten nuts.

Operate the brake by pulling the hand brake mounted on

the battery hood. The pulled hand lever tensions cables

connected to a brake shoe at each brake assembly, thereby

Removal and Replacement

applying the brakes.

As shown in illustration below, with these notes:

Press the button on the front side of hand brake, then the

parking brake will be released. This handle releases the

• Adjust position of interlock and indicator switches

ratchet, and a return spring returns the pedal and cable to

with pedal upstop against tab on bracket. Switch

the off position. The ratchet also operates the parking

contacts should snap from their operated contact

brake interlock switch and the parking brake indicator

position to their normal position when pedal is

light switch.

depressed one ratchet click.

• Torque switch mounting nuts 0.8-1.0 N⋅m (7-9

lbf⋅in). Torque bracket mounting nuts 20-23 N⋅m

Adjustment

(177-210 lbf⋅in).

1. With the lever fully lower, upstop against tab on

• Apply a thin coat of Clark lubricant, part

bracket, adjust slack out of brake cables and tighten

#1802155, to ratchet teeth and ball end of wire

adjusting/locking nuts.

rope prior to assembly.

Parking Brake handle Boot

Parking Brake handle

Parking Brake Cable

Switch Mounting Plate

Switch

Adjusting/

Locking Nuts

SM 765, Sep ’06

Parking Brake Service • 23-6-1

Group 25, Steering Column and Gear

Section 1

Steering System Specifications and Description

Specifications

Description

Steering System Type: Hydrostatic power steering with

All truck models have a hydrostatic power steering sys-

load sensing, dynamic signal neutral circuit.

tem, which is supplied with oil pressure from the main

hydraulic pump. The steering hand wheel operates the

Steering System Relief Pressure Setting: 10000 kPa (1450

steering gear (steering control unit), which directs oil flow

psi)

to the steering cylinder on the steer axle. A steering sys-

tem pressure relief valve is built into the steering control

unit to prevent over-pressurization of the steering system.

The pressure relief setting can be tested by installing a test

Service Intervals

fitting install Quadrigage at pressure inlet of steering gear.

Check the steering system relief pressure annually or after

The power steering gear is a remote positioning control

every 2000 hours of operation. Make a visual inspection

valve that senses the input signal from the steering hand

of steering control unit hydraulic fittings periodically to

wheel, multiplies this signal to assist in reducing the steer-

ensure that the fittings are tight with no leakage.

ing effort, and causes the steering axle to turn the wheels

to the desired position by supplying hydraulic flow to the

Fastener Torques

steering cylinder.

The steering gear is connected to the bottom of the steer-

Steering Handwheel Nut: 35-45 N⋅m (25.5-33.5 ft-lb)

ing column. When the steering hand wheel is turned, it is

linked mechanically to the steering gear spool and causes

this spool valve to shift from its closed neutral position to

a “turn” position that allows oil under pressure to flow to

the steering cylinder.

When the steering hand wheel stops turning, centering

springs in the valve automatically center the spool, stop-

ping the flow of oil to the cylinder.

The low pressure oil from the opposite side of the steering

cylinder is returned through the opposite port in the gear.

It is controlled by the same spool as the high pressure

port.

In the event of a pump failure, the steering gear can gener-

ate sufficient hydraulic power by movement of the steer-

ing handwheel to serve as a limited steering method. An

internal check valve automatically closes to divert this

generated oil flow to the proper port of the steering cylin-

der. The handwheel turning effort is considerably higher,

however, than with power steering.

SM 765, Nov ’06

Steering System Specifications and Description • 25-1-1

Group 25, Steering Column and Gear

The column tilt lock mechanism allows the operator to

The cover can be removed for service to steering column

adjust the steering column. The column tilt lever knob

components. The entire column can be removed for ser-

releases the adjustment setting and the column returns to

vice or replacement.

the up position by the use of gas springs. The tilt lock

mechanism, the directional control lever are protected by

the steering column cover.

Locker Switch

Steer Handle

Direction Control

Light Switch Lever

Assembly

Steer Handle

Screw

Column Upper Cover

Tilt Lock Lever

Gas Spring

Tilt Lock Assembly

Column Lower Cover

Wire Harness

Column Outside

Column Inside

25-1-2 • Steering System Specifications and Description

SM 765, Nov ’06

Group 25, Steering Column and Gear

Section 2

Steering System Troubleshooting

No steering

Handwheel kickback

• Hydraulic fluid level very low.

• Check valve faulty (or not in system).

• Air in hydraulic oil.

Slow steering response

• Steering column sections not connected properly.

• Hose broken.

• Oil viscosity too high.

• Hydraulic pump contaminated or defective.

• Contaminated or defective steering gear.

• Priority valve spool stuck.

Chatter conditions

Hard steering

• Loose mountings or linkage. Make certain all

• Hydraulic fluid level low.

mounting fasteners and other linkage is tight.

• Air in hydraulic oil.

• Pressure relief valve set too low and is out of

adjustment; adjust or replace the relief valve.

• Steering gear contaminated or defective.

• Insufficient pump flow. Check pump for leaks and

• Relief valve setting too low; adjust or replace.

see Section 5 of this Group.

• System leaking.

• Axle load too heavy.

Unsatisfactory steering in either direction

• Lack of lubrication.

• Air in system due to excessive wear in steering cyl-

• Defective steering gear.

inder. Check for air in system. Excessive noise or

• Spring in priority valve broken.

foamy condition of hydraulic fluid indicates aera-

tion. Check that air is not entering the system

High number of handwheel turns

through poor threads, cracked, split, or worn hoses,

bad pump seals, bad O-rings, bad gaskets, or loose

• Steering cylinder seal leakage.

connections.

• Worn steering gear.

Worn cylinders result in leakage past the piston.

Overhaul (see Group 26, Section 6) or replace the

Steering handwheel spins freely

steer cylinder.

• Air in system (cavitation).

• Incorrect system pressure due to worn pump.

• Low oil supply.

Replace the relief valve or repair or replace the

hydraulic pump.

• Steering column detached from steering gear.

• Defective steering gear.

Noise during turns

Jerky steering

• Worn bearing(s) in steering arm; replace bearings.

• Worn pin in steering knuckle; replace pin.

• Steering gear malfunction because of worn parts or

contamination. Steering gear may require over-

• Worn bearings in steering knuckle; replace bear-

haul.

ings.

• Steering knuckle is loose; tighten castle nut.

Truck turns in wrong direction

• Hydraulic lines not installed correctly.

SM 765, Nov ’06

Steering System Troubleshooting • 25-2-1

Group 25, Steering Column and Gear

Constant noise from steering axle

Low pressure at the steering gear

• Loose or worn hub bearing cones. Adjust or

• Refer to Group 26.

replace hub bearing cones. Replace bearing cones

and bearing cups as a set.

Steer cylinder rod binding or sticking

• Binding of linkage. With hydraulic flow shut off

Noise when axle pivots

from the cylinder and the rod end uncoupled, the

• Steering axle mountings worn; replace mountings.

rod should slide freely in or out by hand. If the pis-

ton is binding, overhaul or replace the cylinder.

• Steering axle mounting cap(s) loose; tighten

mounting cap(s).

Fluctuating pressure

• Faulty operation of relief valve. Fluctuating pres-

sure or loss of pressure in the system is usually

caused by scales, chips, sludge, or filings that have

lodged between the relief valve and seat. A dam-

aged spring or worn valve may also be the cause of

the trouble. Flush and refill the system and replace

the hydraulic return line filter element.

25-2-2 • Steering System Troubleshooting

SM 765, Nov ’06

Group 25, Steering Column and Gear

Section 3

Steering Column and Component Removal and Replacement

Steering Column and Component Removal

Key Switch Removal

Hand Wheel, Horn Contact Ring, and Directional Control Assembly Removal

Column Tilt Lock Assembly Removal

Steering Gear and Lower Steering Column Removal

Steering Column and Component Replacement

IMPORTANT

Before removing any component for overhaul, make sure the

correct repair parts, seals, and gasket sets are available.

Rocker Switch

Steer Handle

Direction Control

Light Switch Lever

Assembly

Steer Handle

Screw

Column Upper Cover

Tilt Lock Lever

Gas Spring

Tilt Lock Assembly

Column Lower Cover

Wire Harness

Column Inside

Typical Steering Column Assembly

! CAUTION

SAFE PARKING. Before working on truck:

SM 765, Dec ’06

Steering Column and Component Removal and Replacement • 25-3-1

Group 25, Steering Column and Gear

1. Park truck on a hard, level, and solid

switch and pull rear cover smoothly after removing

surface, such as a concrete floor with no

tilt lock leveler.

gaps or breaks.

2. Put upright in vertical position and fully

lower the forks or attachment.

3. Put all controls in neutral. Turn key

switch OFF and remove key.

4. Apply the parking brake and block the

wheels.

Tilt Lock Lever

Steering Column and Component

Removal

Determine which component requires service and check

Cover Screw

the procedure for removing that component. Read the pro-

cedure completely before beginning disassembly.

Hand Wheel, Light Switch Lever, and

NOTE

Directional Control Assembly Removal

Use care when removing the backside cover

as the rocker switch wiring is attached.

1. Disconnect the battery.

4. Disconnect wire connector assembled to direciton

Steer Handle Cover

control lever and light switch lever and remove direc-

tion control lever and light switch lever from steering

column by releasing two (+) screw.

Column Tilt Lock Assembly Removal

Steer Handle Screw

NOTE

The tilt lock assembly is not serviceable; only

Steer Handle Washer

the gas springs are serviceable. The tilt lock

assembly should be removed only for replace-

Steer Handle

ment as a complete assembly.

1. Remove the negative cable of battery.

2. Refer to "Handle, light switch lever and direction

control assembly removal" to remove upper cover.

2. Remove a hand cover and release nut and washer

3. Use (+) drive to remove 4 screws secruing lower col-

securing handle to steering column.

umn lever and then lower cover.

3. Remove 8 screws secruing both column cover using

(+) driver. Disconnect connector assembled on locker

25-3-2 • Steering Column and Component Removal and Replacement

SM 765, Dec ’06

Group 25, Steering Column and Gear

4. Remove 4 bolts secruing tilt assembly to frame. .

2. Remove the four bolts securing the lower column

shaft and steering gear to the bracket on the frame.

Tilt Lock Assembly

Mounting Screw

Steering Gear

3. Remove the lower shaft and steering gear assembly

from the truck.

Steering Gear Removal

1. Put a pan under the truck to catch hydraulic fluid

which will drip when fittings are loosened. Label the

four hose fittings of the steering gear to make sure

they are reassembled correctly. Loosen and remove

the hydraulic fittings at the steering gear. Cap the

ends to prevent fluid leaks. Cap the steering gear

ports to prevent dust and debris from getting into the

steering gear. Keep hydraulic ports and hoses clean.

Steering Gear

SM 765, Dec ’06

Steering Column and Component Removal and Replacement • 25-3-3

Group 25, Steering Column and Gear

Section 4

Stering System Relief Pressure Check and Adjustment

! CAUTION

WARNING

SAFE PARKING. Before working on truck:

Do not use your hands to check for hydraulic

leakage. Use a piece of cardboard or paper to

1. Park truck on a hard, level, and solid

search for leaks. Escaping fluid under pres-

surface, such as a concrete floor with no

sure can penetrate the skin causing serious

gaps or breaks.

injury. Relieve pressure before disconnecting

hydraulic or other lines. Tighten all connec-

2. Put upright in vertical position and fully

tions before applying pressure. Keep hands

lower the forks or attachment.

and body away from pinholes and nozzles

3. Put all controls in neutral. Turn key

which eject fluids under high pressure.

switch OFF and remove key.

If any fluid is injected into the skin, it must

be surgically removed within a few hours by

4. Apply the parking brake and block the

a doctor familiar with this type of injury or

wheels.

gangrene may result.

Description and Operation

Steering System Relief Pressure Setting

Steering system relief pressure settings above the speci-

Check and Adjustment

fied values can cause failure of the hydraulic lines, dam-

age to seals in the steering gear, and ball joint breakage on

This procedure requires installation of a pressure gauge at

the steer axle.

the gauge port on the main hydraulic pump. The pressure

is measured while the steering handwheel is turned fully

The steering system’s pressure relief valve is part of the

in one direction to put the steering system in bypass.

main hydraulic pump assembly. Steering system relief

pressure is adjustable and should be checked if indicated

Steering system relief pressure setting may be checked

by troubleshooting. Use the gauge port on the pump to

using a Mico Quadrigage (Clark Part No. 1800106) or

check steering relief pressure.

with a conventional pressure gauge, 0-20,700 kPa (0-3000

psi).

Steering system relief pressure setting should be 10000

kPa (1450 psi).

1. Tilt the steering column fully forward and raise the

seat deck.

NOTE

If relief pressure is not correct, the problem

may be caused by dirt in the valve or worn

parts, including steering control valve and

main hydraulic pump. Generally, if the relief

pressure measured when the steering system

is in bypass is not correct, the priority

demand valve should be replaced.

SM 765, Dec ’06

Stering System Relief Pressure Check and Adjustment • 25-4-1

Group 25, Steering Column and Gear

2. Clean the port opening and connect the pressure

gauge (also cleaned) to the gauge port on the main

pump.

To increase

To decrease

b. Clockwise adjustment of the relief valve seat

3. Start the engine and let it warm up until it runs

raises the pressure setting at which the valve

smoothly.

relieves pressure ; counterclockwise adjustments

4. Check steering system relief pressure setting at full

lowers the pressure setting at which the valve

throttle. Accelerate engine to full throttle and hold at

relieves pressure.

this speed while taking the pressure readings.

7. Restart engine and repeat steps to read and adjust the

IMPORTANT

relief pressure setting until correct relief pressure is

Do not operate system over relief any longer

set.

than required to read the pressure gauge.

• Once you adjust to the correct relief pressure set-

Prolonged time at relief pressure can result in

ting, reset the core plug in the valve bore.

a damaged pump and valve.

• If the correct relief pressure cannot be gained, con-

sider overhauling or replacing both the priority

5. Turn the steering handwheel in one direction until

valve and the pressure relief valve. See Group 29,

steering cylinder reaches its stop (relief bypass).

“Hydraulic Pump Overhaul” for instruction to

Hold steering handwheel in relief position until pres-

remove, overhaul, and replace the valves on the

sure reading is taken, and then release. Turn off

pump.

engine. Pressure should read between 10000 kPa

(1450 psi).

8. Disconnect the pressure gauge and close the engine

compartment.

6. To adjust the steering pressure relief to 10000 kPa

(1450 psi).

a. Carefully remove the core plug of the steering

pressure relief valve on the main pump by prying

the plug out.

25-4-2 • Stering System Relief Pressure Check and Adjustment

SM 765, Dec ’06

Group 25, Steering Column and Gear

5. Remove meter (gerotor). Be careful not to drop star

Disassembly

(rotor).

Cleanliness is extremely important when repairing a steer-

ing gear. Work in a clean area. Before disconnecting lines,

clean port area of unit thoroughly. Use a wire brush to

remove foreign material and debris from around exterior

joints of the unit.

NOTE

Although not all illustrations show the unit in

a vise, it is recommended to keep the unit in

the vise during disassembly. Follow the

clamping procedures explained throughout

the text.

6. Remove seal from meter.

Meter (Gerotor) End

7. Remove drive spacer(s).

1. Clamp unit in vise, meter end up. Clamp lightly on

8. Remove drive.

edges of mounting area, as shown. Use protective

material on vise jaws. Do not overtighten jaws.

9. Remove spacer plate.

2. Remove capscrews.

10.

10.Remove seal from housing.

Control End

11. Remove housing from vise and place on a clean soft

cloth to protect surface finish. Use a thin-bladed

screwdriver to pry retaining ring from housing.

3. Remove end cap.

4. Remove seal from end cap.

25-5-2 • Steering Gear Overhaul

SM 765, Dec ’06

Group 25, Steering Column and Gear

12. Place assembly so shaft is horizontal. Rotate spool

IMPORTANT

and sleeve until pin is horizontal. Push spool and

Do not bind spool and sleeve in housing.

sleeve assembly forward with your thumbs just far

Rotate spool and sleeve assembly slowly

enough to free seal gland bushing from housing.

when removing from housing.

Remove bushing.

17. Push pin from spool and sleeve assembly.

18. Push spool partially from control end of sleeve, then

remove six centering springs from spool carefully by

hand. Note their position in the unit before they are

removed.

13. Remove quad ring seal from seal gland bushing.

14. Use a thin-bladed screwdriver to pry dust seal from

seal gland bushing. Do not damage bushing.

15. Remove two bearing races and the needle thrust bear-

19. Push spool back through and out of sleeve. Rotate

ing from spool and sleeve assembly.

spool slowly when removing from sleeve.

20. Remove seal from housing.

16. Remove spool and sleeve assembly from cap (14-

hole) end of housing.

21. Remove set screw from housing.

22. Screw a 1/8-inch-24 NC machine screw into end of

check ball seat. Then pull on screw with pliers to lift

seat out of housing.

23. Remove two seals from check valve seat.

24. Tip housing to remove check ball and check ball

retainer.

SM 765, Dec ’06

Steering Gear Overhaul • 25-5-3

Group 25, Steering Column and Gear

Lubricate check ball seat and seals thoroughly before

Parts Inspection

installing seat in housing. When installing seat do not

Inspect all parts for damage, cracks, broken parts, dam-

twist or damage seals. Install check ball seat in hous-

aged threads, corrosion or erosion of surfaces, worn spots,

ing; insert open end of seat first. Push check ball seat

nicks or scratches.

to bottom of hole.

Check all mating surfaces. Replace any parts that have

Install set screw. Use a 5/16-inch Allen wrench to

scratches or burrs that could cause leakage. Discard all old

torque set screw to 11 N⋅m (100 in-lb; 8.3 ft⋅lb). To

seals and replace with new ones.

prevent interference of parts, make sure top of set

screw is slightly below housing mounting surface.

Clean all metal parts in clean solvent. Blow dry with air.

Do not wipe dry with cloth or paper towel because lint or

Assemble spool and sleeve carefully so that the

other matter can get into the hydraulic system and cause

spring slots line up at the same end. Rotate spool

damage. Do not use a coarse grit or try to file or grind

while sliding parts together. Some spool and sleeve

these parts.

sets have identification marks ; align these marks.

Test for free rotation. Spool should rotate smoothly

If parts are left exposed, cover them with a clean cover to

in sleeve with finger tip force applied at splined end.

prevent airborne dust from collecting on them.

Reassembly

Refer to Service Parts Book when ordering replacement

parts. A good service policy is to replace all old seals with

new seals at overhaul.

NOTE

Lubricate all seals (with exception of new

quad ring seal) with clean petroleum jelly

Bring spring slots of both parts in line and stand parts

such as Vaseline.

on end of bench. Insert spring installation tool (avail-

Do not use excessive lubricant on seals for

able as Part No. 6000057) through spring slots of

meter (gerotor) section.

both parts. Position three pairs of centering springs

Make sure all parts are clean and free of

(or two sets of 3 each) on bench so that extended

dust. Before assembly, lightly coat all internal

edge is down and arched center section is together. In

metal parts with oil.

this position, insert one end of entire spring set into

spring installation tool, as shown.

Control End

1. Use a needle-nosed pliers to lower check ball retainer

into check valve hole of housing. Make sure retainer

is straight (not tilted on edge) in housing.

On those units which use the low torque centering

springs, there are two pairs of centering springs (or

two sets of each) and one pair (two) spring spacers.

The spring spacers are installed together between the

two sets of centering springs. The installation proce-

dure is the same as that used on the standard (three

2. Install check ball in housing.

pairs of centering springs) units.

3. Lubricate 5/8-inch diameter seal and 7/16-inch diam-

eter seal. Install seals on check ball seat, as above.

25-5-4 • Steering Gear Overhaul

SM 765, Dec ’06

Group 25, Steering Column and Gear

8. Compress extended end of centering spring set and

13. Install two bearing races and the needle thrust bear-

push into spool sleeve assembly withdrawing instal-

ing in the order shown.

lation tool at the same time.

9. Center the spring set in the parts so that they push

down evenly and flush with the upper surface of the

spool and sleeve.

10. Install pin through spool and sleeve assembly until

pin becomes flush at both sides of sleeve.

14. Install 1-1/4-inch diameter dust seal in seal gland

bushing; flat or smooth side of dust seal must face

down towards bushing.

11. Position the spool and sleeve assembly so that the

splined end of the spool enters the 14-hole end of

15. Install dry quad ring seal in seal gland bushing.

housing first.

Smooth seal in place with your finger. Do not use any

seal that falls freely into pocket of bushing. Seal

should not “fall” into place but should require light

force to seat.

IMPORTANT

Be extremely careful that the parts do not tilt

out of position while being installed. Push

parts gently into place with slight rotating

action; keep pin nearly horizontal. Push the

spool assembly entirely within the housing

bore until the parts are flush at the meter end

or 14-hole end of housing. Do not push the

spool assembly beyond this point to prevent

the cross pin from dropping into the dis-

charge groove of the housing. With the spool

assembly in this flush position, check for free

rotation within the housing by turning with

light finger tip force at the splined end.

12. Place housing on clean, lint free cloth. Install 2-1/8-

inch diameter seal in housing.

SM 765, Dec ’06

Steering Gear Overhaul • 25-5-5

Group 25, Steering Column and Gear

16. Install seal gland bushing over the spool end with a

Meter (Gerotor) End

twisting motion. Tap the bushing in place with a rub-

ber hammer. Make sure the bushing is flush against

18. Clamp housing in vise, as shown. Clamp lightly on

the bearing race.

edges of mounting area. Do not overtighten jaws.

On those units which use the Teflon seal, install the

Teflon back-up ring into the recess cut into the seal

gland bushing. Install the Teflon seal over the spool

end, then carefully install the seal gland bushing over

the spool end using a rotary motion.

NOTE

The seal gland bushing which is used with the

Teflon seal is not the same as the seal gland

bushing used with the standard quad-ring

seal. The seal gland bushing with the Teflon

seal has an identification groove cut into the

outer diameter of the bushing. The grooved

bushings can only be used with the Teflon

NOTICE

seals and the non-grooved bushings used only

Check to ensure that the spool and sleeve are

with the quad-ring seals.

flush or slightly below the surface of the

housing.

IMPORTANT

Clean the upper surface of the housing by

wiping with the palm of clean hand. Clean

each of the flat surfaces of the meter section

parts in a similar way when ready for reas-

sembly. Do not use cloth or paper to clean

surfaces.

19. Install 3-inch diameter seal in housing.

17. Install retaining ring in housing. After installing ring,

tap on ring or pry with screwdriver around entire cir-

cumference of ring to properly seat ring in groove.

20. Install spacer plate. Align bolt holes in spacer plate

with tapped holes in housing.

25-5-6 • Steering Gear Overhaul

SM 765, Dec ’06

Group 25, Steering Column and Gear

21. Rotate spool and sleeve assembly until pin is parallel

24. Install drive spacer(s) when used, in meter.

with port face. Install drive, making sure you engage

drive with pin.

IMPORTANT

Failure to properly install drive and pin may

cause unit to self steer.

25. Install 3-inch diameter seal in end cap.

26. Install end cap on gerotor, and align holes.

NOTE

27. Install 7 dry cap screws in end cap. Pretighten screws

To assure proper alignment, mark spline end

to initial torque of 17 N⋅m (150 in⋅lb), then torque

of drive shaft with a line parallel to slot on

screws to final torque of 31 N⋅m (275 in⋅lb) in the

other end, before installing.

sequence shown.

22. Install 3-inch diameter seal in meter (gerotor).

23. With seal side of meter toward spacer plate, align star

valleys on drive. Note the parallel relationship of ref-

28. Inspect the assembly to be sure all parts have been

erence lines A, B, C, and D in figure. Align bolt

installed and fasteners correctly installed and tight-

holes without disengaging meter from drive. Be sure

ened.

star has engaged drive spline in position shown.

SM 765, Dec ’06

Steering Gear Overhaul • 25-5-7

Group 26, Steer Axle

Section 1

Steering Axle Specifications and Description

Specifications

Service Intervals

Steering System Relief Pressure Setting : 10000 kPa

Steering Linkage Inspection and Lubrication: Every 50-

(1450 psi)

250 hours and each PM.

Steer Cylinder Type : Double-acting, piston-type

Steer Wheel Bearing Inspection and Lubrication: Every

50-250 hours of operation.

Turning Arc : 83° maximum inside turning angle

59° maximum outside turning angle.

Steer Cylinder Seals Leakage Check: Every 50-250 hours

and each PM.

Bearing Grease : Grade No. 2 EP multi-purpose grease,

Clark Part MS-107C.

Steer Axle Mounting Inspection: Every 50-250 hours and

each PM.

Fastener Torques

Power Steering Relief Pressure Check: Every year or 2000

hours of operation.

Steer Axle Mounting Bolts: 170-190 N⋅m (125-140 ft-lb)

Cylinder to Axle Mounting Bolts: 280-320 N⋅m (205-

Description

234.5 ft-lb)

The steer axle has the steer cylinder, steer knuckles, and

Steering Link to Steering Knuckle Nuts: 135-150 N⋅m

steering links mounted on it. All these components can be

(98-110 ft-lb)

removed, serviced, and replaced.

Steer Knuckle King Pin Castle Nuts: See installation pro-

The steering gear (steering control unit) at the base of the

cedures in Section 4, “Steer Axle Overhaul.

steering column directs hydraulic fluid to one end or the

other of the steer cylinder to pivot the steer wheels.

The steer axle is bolted to the truck frame. The steer cylin-

der is connected to the steering knuckles by steer links.

Mounting trunnions allow the axle to tilt independently of

the truck and “silent” mounts cushion the axle on the trun-

nions.

All bearings used in the steer axle linkage have lubrication

fittings and are serviceable. Axle removal, replacement,

and service for all components, including overhaul of the

steer cylinder, is explained in the Sections for this Group.

SM 765, Dec ’06

Steering Axle Specifications and Description • 26-1-1

Group 26, Steer Axle

Section 2

Steering Axle Wheel Bearing maintenance and Adjustment

Wheel Bearing Check

Wheel Bearing Lubrication

Bearing Disassembly

Bearing Reassembly

Wheel Bearing Adjustment

IMPORTANT

Before removing any component for overhaul, make sure the correct repair parts, seals, and gasket sets

are available.

movement, the bearings require additional service and/or

! CAUTION

adjustment.

SAFE PARKING. Before working on truck:

1. Park truck on a hard, level, and solid

Wheel Bearing Lubrication

surface, such as a concrete floor with no

These procedures cover bearing lubrication for steer

gaps or breaks.

wheels used on the truck ; pneumatic-tire wheels which

2. Put upright in vertical position and fully

are mounted on a hub that contains the bearing compo-

lower the forks or attachment.

nents. Use the procedures to clean, repack and adjust bear-

3. Put all controls in neutral. Turn key

ings for both the pneumatic-tire hub.

switch OFF and remove key.

The bearing components and arrangement are the same

4. Apply the parking brake and block the

for both the pneumatic types. Instructions for repacking/

wheels.

lubricating the bearing components apply to both types.

5. Remove Battery Connector.

Pneumatic-Tire

Wheel Mounting

Wheel Bearing Check

Hub

Wheel bearings check should be performed every PM.

Wheel bearings need adjustment only after 2000 hours or

as needed. It is recommended that you clean and repack

the bearings before adjustment. Check hourmeter total

hours and refer to the truck’s PM schedule. See steer

wheel bearing lubrication procedure below.

To check the steer wheel bearings for excessive free play

or looseness:

1. Grasp the wheel with both hands and try to move it

by a rocking motion top-to-bottom.

Steer Axle Knuckle

2. Try to pull it in and out along the wheel spindle.

Watch for excessive free movement in wheel bearings or

wheel-assembly

steering knuckle bearings. There should be a small

amount of free movement. If the wheel has excessive free

SM 765, Dec ’06

Steering Axle Wheel Bearing maintenance and Adjustment • 26-2-1

Group 26, Steer Axle

Bearing Disassembly

2. Refer to the exploded view illustration of the wheel

bearing assembly. Loosen and remove the hubcap

1. Be sure truck is parked and blocked up correctly and

from wheel or hub. You may have to lightly tap hub

safely to raise steer wheels off the floor. Refer to

cap with a hammer and chisel and use a pry bar to

“Lifting, Jacking, and Blocking,” in the Group “SA.”

loosen. Be careful not to damage mounting surfaces.

Remove O-ring from hubcap.

NOTE

Because of the heavy weight of the wheel and

3. Clean the excess grease from around the wheel nut.

tire, it is suggested to first remove the wheel

4. Remove cotter pin, loosen and remove wheel nut and

and tire assembly from spindle when servic-

bearing washer.

ing the bearings to avoid damage to the

grease seal when the wheel hub is moved off

or on the spindle. It also makes the work sim-

pler and easier.

Wheel Bearing Assembly.

26-2-2 • Steering Axle Wheel Bearing maintenance and Adjustment

SM 765, Dec ’06

Group 26, Steer Axle

5. Pull the wheel or hub off the spindle. Support the

1. Install new inner and outer bearing cups by pressing

wheel or hub to avoid dragging the grease seal at the

into hub or wheel. Be sure cups are fully seated in

back side across the thread on spindle end.

bore.

6. Clean the old grease out of center of the wheel or

hub.

7. To remove inner bearing and seal, lay wheel or hub

down with outer edge up (support hub on blocking).

Remove the inner bearing cone and grease seal, using

a brass drift pin, rod, or piece of pipe to drive the

bearing and seal out of the hub.

2. Pack the bearings with grease and install the inner

bearing in the hub or wheel.

8. Clean and inspect the bearing cups and cones for

3. Pack cavity between bearing and grease seal half full

wear or other damage. Replace, as necessary.

with grease.

IMPORTANT

4. Install new grease seal in hub or wheel inner bore.

Keep serviceable bearing cups and cones

Apply coating of grease to inside diameter of seal

matched together. Always replace bearing

lips prior to assembly, then install seal in hub or

cups and cones as a set.

wheel bore.

9. Inspect grease seal for wear and damage. Replace as

necessary. It is recommended to install a new grease

seal whenever old ones are removed.

10. Use a standard puller to remove bearing cups from

hub or wheel if bearings require replacement.

Bearing Reassembly

NOTE

5. Carefully press or tap grease seal into place with

Use Grade No. 2 EP multi-purpose grease,

asoftfaced mallet until seal is seated in bottom of

Clark MS-107C.

bore.

6. Install hub or wheel on spindle. Be careful not to

damage grease seal lip when moving the hub over the

end of spindle and threads.

7. Pack cavity in hub between bearings one-half full

with grease.

SM 765, Dec ’06

Steering Axle Wheel Bearing maintenance and Adjustment • 26-2-3

Group 26, Steer Axle

Install the outer wheel bearing after it has been

Wheel Bearing Adjustment

packed with grease.

The steer wheel bearings are retained and adjusted by the

wheel nut.

NOTE

You should clean and repack the wheel bear-

ings before performing a wheel bearing

adjustment. See “Wheel Bearing Lubrica-

tion” in this Section for the complete proce-

dure.

Install bearing washer and hand tighten wheel nut.

CAUTION

SAFE PARKING. REFER TO PAGE 1.

Make sure the truck is parked on a level, hard sur-

face, the upright is fully lowered, the drive wheels

are chocked, and the steer wheels are jacked and

blocked securely. Refer to “Lifting, Jacking, and

Blocking” for safe procedures.

Remove hubcap.

Remove and discard cotter pin.

Loosen wheel nut.

10.

Rotate hub or wheel counter clockwise and torque

wheel nut to 27-31 N⋅m (20-23 ft-lb).

After wheel nut is loosened, hit the top of wheel to

loosen the bearings. This moves the bearings free of

11.

Back wheel nut up until it is loose.

their seated, running position.

12.

While turning the hub or wheel counter clockwise,

Rotate hub or wheel counter clockwise and torque

torque the wheel nut to 2.3-2.8 N⋅m (1.7-2 ft-lb).

wheel nut to 27-31 N⋅m (20-23 ft-lb).

13.

Back up wheel nut to nearest slot and install new cot-

Back wheel nut up until it is loose.

ter pin. Bend cotter pin tabs.

While turning the hub or wheel counter clockwise,

14.

Recheck for correct bearing adjustment by rotating

torque the wheel nut to 2.3-2.8 N⋅m (1.7-2 ft-lb).

the wheel by hand. Wheel should rotate freely or

with only slight “drag”. Readjust bearings by adjust-

Back up wheel nut to nearest castellation slot and

ing wheel nut as necessary to avoid binding in bear-

install new cotter pin.

ings.

10.

Recheck for correct bearing adjustment by rotating

15.

Pack the area around wheel nut with grease.

the wheel by hand. Wheel should rotate freely or

with only slight “drag”. Readjust bearings by adjust-

16.

Refit O-ring on hubcap and install hubcap by tapping

ing wheel nut as necessary to avoid binding in bear-

into place with a rubber or plastic-faced hammer.

ings.

11.

Bend cotter pin tabs over.

12.

Pack the area around wheel nut with grease.

13.

Refit O-ring on hubcap if removed or replaced and

install hubcap by tapping into place with a rubber or

plastic-faced hammer.

26-2-4 • Steering Axle Wheel Bearing maintenance and Adjustment

SM 765, Dec ’06

Group 26, Steer Axle

! CAUTION

SAFE PARKING. Before working on truck:

1. Park truck on a hard, level, and solid

surface, such as a concrete floor with no

gaps or breaks.

2. Put upright in vertical position and fully

lower the forks or attachment.

3. Put all controls in neutral. Turn key

switch OFF and remove key.

Disconnect cylinder lines here.

4. Apply the parking brake and block the

wheels.

CAUTION

Steer Axle Removal

Axle must be supported before any attaching

fasteners are removed.

Remove the counterweight before removing the steer

axle. Refer to Group 38, Section 2, “Counterweight

If another lift truck is used to temporarily support

Removal and Replacement.” (It is possible to remove

axle while removing, put forks in center of carriage

the steer axle without removing the counterweight

about 305 mm (12 in) apart. Move forks under axle

but much easier if it is removed).

and raise itjust toremoveits weight from mounting-

bolts. Or use a portable floor jack to carefully support

! WARNING

the axle at its center section.

Do not remove the counterweight unless you

Loosen and remove nuts from axle mounting bolts,

have training and are familiar with the cor-

front and rear.

rect procedures. Counterweights can fall if

not handled correctly and cause severe injury

• Remove the mount plates from the bottom of the

or death.

trunnion mounts of the steer axle (Figure A.).

Remove the mounting bolts.

! WARNING

Lower the axle allowing its weight to pull the silent

blocks out of frame recesses. Watch the silent blocks

Do not raise truck by hoisting on overhead

to be sure they release freely from frame. You may

guard or by jacking or lifting on counter-

have to loosen blocks with a pry bar if they bind.

weight.

Carefully withdraw the axle from beneath the truck

Block the drive wheels of the truck and raise and

and move to safe storage.

block the rear end. Remove steer wheels. See “Lift-

ing, Jacking, and Blocking” in Group “SA” for safe

procedures to jack the truck.

! CAUTION

Make sure truck is correctly raised and

safely blocked using hardwood blocks under

the frame. Be sure the blocking will permit

installation of the axle without disturbing the

blocking.

loosen and remove hydraulic steering lines from

steering cylinder. Plug fittings and cap open ends of

lines. Keep all hydraulic fittings and openings clean.

26-3-2 • Steering Axle Removal and Replacement

SM 765, Dec ’06

Group 26, Steer Axle

Make sure that the silent blocks are positioned cor-

rectly front and rear on the steer axle trunnions at the

Old Steer Axle

start of installation. Align the silent blocks square

with the axle.

Use a fork lift truck or mobile floor jack to tempo-

Steer Axle

rarily support and raise the axle into place under the

truck. If another lift truck is used to handle axle, cen-

ter the forks with about 305 mm (12 in) spread

between them. Place steer axle assembly in secure

position on fork tips.

If hydraulic jack is used, be sure axle is securely sup-

Steering Link

ported on jack pad.

WARNING

Silent Mount

Heavy components can fall and cause severe

Steering Knuckle

injury. Keep your body clear at all times.

New Steer Axle

Install axle assembly into frame by slowly raising it

up while guiding silent block bushings into frame

sockets.

Steer Axle

Install silent block mounting bolts through frame

socket holes and silent block, front and rear.

Reset the two mounting plates under the silent blocks

Steering Link

of the axle.

Install silent mount fasteners and tighten to 240-265

N⋅m (180-196 ft-lb).

Remove temporary axle support from under truck.

Connect the hydraulic lines to steering cylinder.

Steering Knuckle

Tighten fittings to 12-14 N⋅m (106-123 in-lb; 8.8-

10.3 ft-lb).

Silent Mount

IMPORTANT

Steer Axle Mounting

Make sure all fittings and openings on the

Steer Axle Replacement

hydraulic lines are clean.

Replacement is the reverse of removal. Refer to Figure A

for replacement.

! CAUTION

Make sure truck is correctly raised and

safely blocked using hardwood blocks under

the frame. Be sure the blocking will permit

installation of the axle without disturbing the

blocking.

1. If silent blocks have been removed from axle, install

new silent block assemblies. Use a rubber or plastic

mallet to seat the silent mounts onto the axle trun-

nions.

SM 765, Dec ’06

Steering Axle Removal and Replacement • 26-3-3

Group 26, Steer Axle

9. Carefully raise the truck off the blocking as described

in “Lifting, Jacking and Blocking”. Remove the

blocking and lower the truck to the floor.

10. If removed, reinstall countenveight; refer to Group

38, Section

2, “Counterweight Removal and

Replacement”.

11. Check the axle and steering system for proper opera-

tion. Operate the steering gear to move the steer

wheels to maximum travel in both directions. Note

any unusual motion or noise.

If the system appears to be operating correctly, drive

the truck slowly. Fully steer the vehicle in each direc-

tion and check response.

12. Check steering cylinder hose line connections and

cylinder rod seals for any evidence of oil leakage

before returning the truck to service.

26-3-4 • Steering Axle Removal and Replacement

SM 765, Dec ’06

Group 26, Steer Axle

Remove and discard cotter pin from kingpin castel-

Preparation For Steer Axle

lated nut. Remove the nut.

Disassembly and Over haul

NOTE

Cleanliness is of extreme importance in the

Kingpin castel-

lated Nut

repair and overhaul of this assembly.

• Before starting disassembly, thoroughly clean the

axle assembly of all accumulations of dirt, oil, cor-

rosion, and other substances to prevent contamina-

tion of the parts during disassembly and overhaul.

• Work in a clean area.

• Keep all parts in order as disassembly progresses.

Kingpin

Take care to properly identify each part and its

Retainer Pin

order of removal. If necessary, keep notes and put

markings on parts using a non-destructive marker

such as a grease pencil or felt-tipped pen.

Drive the kingpin down and out of the assembly.

• If necessary, see Section 3, “Steer Axle Removal

Remove the steering knuckle. Note right and left

and Replacement,” for the procedures to remove

knuckle parts.

the steer axle from the truck.

IMPORTANT

• See Section

5, “Steer Cylinder Removal and

Do not let the knuckle or pin fall when the

Replacement,” for the procedures to remove the

pin is removed.

steering cylinder and steering links from the steer

axle.

Remove the kingpin retainer pin from the base of

• See Section 6, “Steering Cylinder Overhaul,” to

the kingpin.

disassemble the steer cylinder.

Remove the knuckle bearing washers, dust covers,

upper and lower grease seals, bearings, and bear-

Steer Axle Disassembly

ing cups from the assembly.

To disassemble the steering knuckle, kingpin, and bearing

from the steer axle, it is not necessary to remove the axle

from the truck.

1. Remove the snap ring from the bottom of the steering

link pin and remove the pin. Steering link is free to

be removed from the cylinder rod and knuckle.

Bearing cups may be removed by hand, by using a bearing

puller, or by tapping out using a brass drift pin.

26-4-2 • Steering Axle Overhaul

SM 765, Dec ’06

Group 26, Steer Axle

3. Set the retainer pin into the king pin and slide the

Parts Inspection

king pin into the steer axle/knuckle bore.

1. Clean all bearings, cups, seals, pins, and other parts

IMPORTANT

in an approved cleaning fluid.

Make sure that retainer pin enters the hole in

2. Inspect all parts for scratches, chips and wear. Check

the underside of the axle

the steering arms of the knuckles to be sure they are

Kingpin castel-

not bent or twisted. Check all threaded parts for dam-

lated Nut

age.

3. Replace all parts which show damage.

4. If parts are to be left exposed, coat all mating sur-

faces of parts with a light coating of engine oil.

Steer Axle Reassembly

Kingpin

Recommended greasing procedure:

Retainer Pin

a. Use Grade No. 2 EP multi-purpose grease, Clark

4. Reset the kingpin castellated nut to the top of the

MS-107 or equivalent.

kingpin. Torque nut to 50-60 N⋅m (36.5-44 ft-lb).

b. Pack all tapered roller bearings with grease

before assembly.

5. Rotate the steer knuckle three times through its full

range of movement. Check to be sure that it is free to

c. Pack knuckle pin (bearing) seals with grease

rotate in the bearings without binding.

before assembly.

d. Fill steer link sockets with grease through grease

6. Loosen the kingpin nut and retorque the nut to 30-

35N⋅m (22.2-25.5 ft-lb).

fittings after axle is assembled.

7. Advance the nut to the next castellated slot and

1. Install the upper and lower knuckle bearing cups into

lock the nut into position with a new cotterpin.

the knuckle housing bore. Tap into place with a brass

Bendcotterpin tabs over.

drift pin or equivalent.

8. Replace steering link pin and snap ring to join the

cylinder rod to the steering link and knuckle.

9. Reinstall grease fitting in knuckle housing and lubri-

cate with recommended grease.

IMPORTANT

Make sure that bearing cup is fully seated

against the shoulder in bore. There must be

no gap left between cup and the shoulder in

the bore at assembly.

2. Apply grease to upper and lower knuckle bearings

and install bearings, grease seals, and washers to

bores of knuckle.

SM 765, Dec ’06

Steering Axle Overhaul • 26-4-3

Group 26, Steer Axle

Section 5

Steering Cylinder Removal and Replacement

! CAUTION

SAFE PARKING. Before working on truck:

Steer Cylinder Rod

1. Park truck on a hard, level, and solid

Steering Link Pin

Steering Link

2. surface, such as a concrete floor with no

gaps or breaks.

3. Put upright in vertical position and fully

lower the forks or attachment.

4. Put all controls in neutral. Turn key

switch OFF and remove key.

5. Apply the parking brake and block the

wheels.

Old Steer Axle

Steering Link Bearing

Snap Ring

Steer Cylinder Removal

Steering Link Pin

The steer cylinder can be removed from the steer axle for

overhaul or replacement without removing the steer axle

Cylinder Rod

from the truck. The cylinder should be overhauled or

Steering Link

replaced if steering problems or troubleshooting informa-

tion indicate the cylinder is malfunctioning. See Group

2.5, Section 2, “Steering System Troubleshooting,” for

steering problem diagnoses. See Section 6 in this Group

for steer cylinder overhaul procedures.

1. Place a dram pan under the steer cylinder and remove

New Steer Axle

the hydraulic lines from the cylinder fittings. Cap fit-

Cotter Pin

tings and lines to prevent fluid from leaking and to

protect the components and hydraulic system from

NOTE

dust and dirt. Label hoses and fittings for correct

Mark left-side and right-side parts for cor-

reassembly.

rect reassembly.

3. Tap steer link pin upward until it clears the steering

link bearing and remove the pin.

4. Remove steer link bearing from steering link-to-cyl-

inder rod end bore.

5. Rotate the steering link away from the cylinder rod

end.

6. Repeat steps 1 through 5 for the opposite side of the

steer cylinder.

7. Remove the four steer cylinder mounting bolts and

Remove fittings.

washers from the steer axle. Removal torque on these

bolts can be as high as 405 N⋅m (300 ft-lb).

2. Remove the snap ring from the bottom of the steering

link pin. Steering link pin attaches steer cylinder rod

end to steering link.

SM 765, Dec ’06

Steering Cylinder Removal and Replacement • 26-5-1

Group 26, Steer Axle

Cylinder is now ready to be removed from the steer axle

body. Cylinder must be lifted off dowel pins positioning

cylinder to axle body.

CAUTION

! CAUTION

Cylinder is somewhat heavy and bulky.

When removing cylinder from mounting be

When remounting cylinder to steer axle

prepared to lift and move the full weight of

body, be prepared to lift and maneuver the

the cylinder.

full weight of the cylinder as you set it into

position.

Parts Inspection

2. Position the steering link with the cylinder rod end.

Reuse steer link bearing if still serviceable. Install

Completely inspect all parts:

new bearings if scoring or wear marks are evident or

1. Clean all bearings, cups, seals, pins, and other parts

if the bearings do not operate smoothly.

in an approved cleaning fluid.

2. Inspect all parts for scratches, chips, scoring, and

uneven or heavy wear. Check steering links to be sure

Steer Cylinder Rod

they are not bent or twisted. Check all threaded parts

Steering Link Pin

for damage.

Steering Link

3. Replace all parts showing excessive wear or signs of

damage.

4. If parts are to be left exposed, coat all mating sur-

faces of parts with a light layer of engine oil. Keep all

parts clean and covered.

5. Remove and clean all grease fittings before reassem-

Old Steer Axle

Steering Link Bearing

bling cylinder components.

Snap Ring

Refer to Section 6, “Steer Cylinder Overhaul”, if pressure

check or troubleshooting tips indicate a problem with

Steering Link Pin

steer cylinder performance.

Cylinder Rod

Steering Link

Steer Cylinder Replacement

1. Remount the steer cylinder onto the steer axle dowel

pins; set bolts and washers in place and torque

mounting bolts to 280-320 N⋅m (205-234.5 ft-lb).

New Steer Axle

Cotter Pin

26-5-2 • Steering Cylinder Removal and Replacement

SM 765, Dec ’06

Group 26, Steer Axle

3. Rotate steering link into cylinder rod end and align

bearing hole with rod end.

4. Tap pin through steer link bearing hole with snap

ring groove on lower end.

IMPORTANT

Make sure bearing is properly aligned with

pin in the hole.

5. Install the snap ring to the steering link pin.

6. Repeat steps 1 to 5 for rod end-to-steering link con-

nection for opposite side.

7. Clean and replace hydraulic hoses on correct, clean,

cylinder fittings. See Group 40, Hydraulic Fitting

Tightening Procedure” for replacement procedures.

Replace fittings.

8. Check to be sure all lube fittings are installed. Fill all

lubrication points with correct lubricant. See recom-

mended greasing procedure above.

9. Test function of steer cylinder before returning the

truck to service.

SM 765, Dec ’06

Steering Cylinder Removal and Replacement • 26-5-3

Group 26, Steer Axle

Remove gland from opposite end of steer cylinder.

Preparation for Steer Cylinder Disas-

sembly and Over haul

Remove the seal and O-ring set from the piston. Dis-

card seals. Replace with new seal set at assembly.

Refer to Section 5 for removal of steer cylinder from the

steer axle body.

IMPORTANT

Cleanliness is of extreme importance in the

repair and overhaul of this assembly.

Overhaul steer cylinder only in a clean, dust-free

location, using clean tools and equipment. Dirt or grit

will damage the highly-machined surfaces and will

result in leakage or premature failure of components.

Cleanliness of the hydraulic circuit is extremely

important to the proper operation and maintenance of

the system. Be sure the work area is clean.

Remove (inner) gland packing (O-ring) seal. Replace

Before disassembly, the exterior of the steer cylinder

with new seals at assembly.

should be carefully cleaned to remove all dirt and

grease accumulation.

Be sure all hydraulic fluid has been removed from

the cylinder. Stroking the piston rod will help force

the fluid out.

Before starting disassembly, the steer cylinder should

be carefully examined to determine if there is any

external damage.

Steer Cylinder Disassembly

Clamp the steer cylinder assembly in a vise. Wrap

the cylinder in a course cloth to prevent slipping and

scratching. Use extreme caution when tightening vise

Remove the rod (U-cup) seal and rod wiper from

and do not overtighten; cylinder can be bent, dis-

gland and discard. Note direction of seal and wiper

torted, and potentially destroyed.

seating for correct reassembly. Replace with new

seals and wipers at assembly.

Remove one gland by pulling it from cylinder barrel

and pulling it off the piston rod.

Parts Inspection

Carefully clean all parts in an approved solvent and

place on a clean surface.

Check the piston for chips, cracks, and looseness on

the rod. If loose, replace rod and piston assembly.

Be sure the piston-seal groove in the piston is

smooth, true, and undamaged.

Check the piston rod for damage. Look for scratches,

grooves, gouges, pitting, corrosion or other evidence

of unusual wear. Minor surface damage may be

repaired by use of fine abrasion cloth or stoning.

Remove the piston and rod assembly from the Cylin-

Deeper damage will require replacement of piston

der.

rod assembly.

26-6-2 • Steer Cylinder Overhaul

SM 765, Dec ’06

Group 26, Steer Axle

5. Carefully inspect the cylinder internal bore for wear,

scratches, corrosion or other damage. Check the out-

side for damage. Inspect all welds for cracks.

6. Inspect the cylinder ports and threads to be sure they

are free of contamination and that the threads are

clean and not damaged.

7. Check the gland for cracks or damage that could

cause failure.

8. Deep gouges or pitted surfaces require replacement

of parts.

9. Put a light coating of hydraulic fluid on all parts. If

parts are to be left disassembled for a period of time,

3. Install new gland packing (O-ring) seal on inner end

such as overnight, they should be covered with a

of gland.

clean cloth.

Steer Cylinder Reassembly

Check to make sure the overhaul kit you have is correct

and that all parts are included.

IMPORTANT

Be sure inside of cylinder and all parts are

clean before starting reassembly.

Assemble cylinder carefully to prevent dam-

age to seal lips and O-rings. Seals should be

lubricated with hydraulic oil to assist assem-

bly into cylinder barrel and gland. Heating

seal rings in boiling water before starting

assembly will aid in assembly.

4. Install new rod wiper and rod (U-cup) seal in outer

end of gland.

1. Install new O-ring seal on the piston.

IMPORTANT

2. Install new piston seal over the O-ring seal.

Be sure the rod wiper and rod (U-cup) seal

are installed in the correct directions.

5. Lightly lubricate the cylinder and gland mating sur-

faces with hydraulic oil before assembly.

SM 765, Dec ’06

Steer Cylinder Overhaul • 26-6-3

Group 26, Steer Axle

Specifications

Service Intervals

Steering System Relief Pressure Setting : 10000 kPa

Steering Linkage Inspection and Lubrication: Every 50-

(1450 psi)

250 hours and each PM.

Steer Cylinder Type : Double-acting, piston-type

Steer Wheel Bearing Inspection and Lubrication: Every

50-250 hours of operation.

Turning Arc : 100° maximum inside turning angle

75° maximum outside turning angle.

Steer Cylinder Seals Leakage Check: Every 50-250 hours

and each PM.

Bearing Grease : Grade No. 2 EP multi-purpose grease,

Clark Part MS-107C.

Steer Axle Mounting Inspection: Every 50-250 hours and

each PM.

Fastener Torques

Power Steering Relief Pressure Check: Every year or 2000

hours of operation.

Steer Axle Mounting Bolts: 240-270 N⋅m (177-200 ft-lb)

Cylinder to Axle Mounting Bolts: 100-110 N⋅m (74-81 ft-

Description

lb)

The steer axle has the steer cylinder, steer knuckles, and

Steering Link to Steering Knuckle Nuts: 135-150 N⋅m

steering links mounted on it. All these components can be

(98-110 ft-lb)

removed, serviced, and replaced.

The steering gear (steering control unit) at the base of the

steering column directs hydraulic fluid to one end or the

other of the steer cylinder to pivot the steer wheels.

The steer axle is bolted to the truck frame. The steer cylin-

der is connected to the steering knuckles by steer links.

Mounting trunnions allow the axle to tilt independently of

the truck and “silent” mounts cushion the axle on the trun-

nions.

All bearings used in the steer axle linkage have lubrication

fittings and are serviceable. Axle removal, replacement,

and service for all components, including overhaul of the

steer cylinder, is explained in the Sections for this Group.

26-7-2 • Pivot-Turn Steering Axle Maintenance

SM 765, Dec ’06

Group 26, Steer Axle

IMPORTANT

Wheel Bearing Lubrication

Before removing any component for over-

These procedures cover bearing lubrication for steer

haul, make sure the correct repair parts,

wheels used on the truck ; pneumatic-tire wheels which

seals, and gasket sets are available.

are mounted on a hub that contains the bearing compo-

nents. Use the procedures to clean, repack and adjust bear-

! CAUTION

ings for both the pneumatic-tire hub.

The bearing components and arrangement are the same

SAFE PARKING. Before working on truck:

for both the pneumatic types. Instructions for repacking/

1. Park truck on a hard, level, and solid

lubricating the bearing components apply to both types.

surface, such as a concrete floor with no

gaps or breaks.

Pneumatic-Tire

Wheel Mounting

2. Put upright in vertical position and fully

Hub

lower the forks or attachment.

3. Put all controls in neutral. Turn key

switch OFF and remove key.

4. Apply the parking brake and block the

wheels.

5. Remove Battery Connector.

Wheel Bearing Check

Wheel bearings check should be performed every PM.

Steer Axle Knuckle

Wheel bearings need adjustment only after 2000 hours or

wheel-assembly

as needed. It is recommended that you clean and repack

the bearings before adjustment. Check hourmeter total

hours and refer to the truck’s PM schedule. See steer

wheel bearing lubrication procedure below.

To check the steer wheel bearings for excessive free play

or looseness:

1. Grasp the wheel with both hands and try to move it

by a rocking motion top-to-bottom.

2. Try to pull it in and out along the wheel spindle.

Watch for excessive free movement in wheel bearings or

steering knuckle bearings. There should be a small

amount of free movement. If the wheel has excessive free

movement, the bearings require additional service and/or

adjustment.

26-7-4 • Pivot-Turn Steering Axle Maintenance

SM 765, Dec ’06

Group 26, Steer Axle

Bearing Disassembly

a brass drift pin, rod, or piece of pipe to drive the

bearing and seal out of the hub.

Be sure truck is parked and blocked up correctly and

safely to raise steer wheels off the floor. Refer to

“Lifting, Jacking, and Blocking,” in the Group “SA.”

NOTE

Because of the heavy weight of the wheel and

Bearing &

tire, it is suggested to first remove the wheel

Cone

and tire assembly from spindle when servic-

ing the bearings to avoid damage to the

grease seal when the wheel hub is moved off

Grease Seal

or on the spindle. It also makes the work sim-

pler and easier.

Refer to the exploded view illustration of the wheel

Clean and inspect the bearing cups and cones for

bearing assembly. Loosen and remove the hubcap

wear or other damage. Replace, as necessary.

from wheel or hub. You may have to lightly tap hub

IMPORTANT

cap with a hammer and chisel and use a pry bar to

loosen. Be careful not to damage mounting surfaces.

Keep serviceable bearing cups and cones

Remove O-ring from hubcap.

matched together. Always replace bearing

cups and cones as a set.

Clean the excess grease from around the wheel nut.

Remove cotter pin, loosen and remove wheel nut and

Inspect grease seal for wear and damage. Replace as

necessary. It is recommended to install a new grease

bearing washer.

seal whenever old ones are removed.

Steering Axle Knuckle

10.

Use a standard puller to remove bearing cups from

Spindle

hub or wheel if bearings require replacement.

Tire and Whel

Bearing

Washer

O-ring

Hub cab

Wheel nut and

Cotter pin

Wheel Bearing Assembly.

Pull the wheel or hub off the spindle. Support the

wheel or hub to avoid dragging the grease seal at the

back side across the thread on spindle end.

Clean the old grease out of center of the wheel or

hub.

To remove inner bearing and seal, lay wheel or hub

down with outer edge up (support hub on blocking).

Remove the inner bearing cone and grease seal, using

SM 765, Dec ’06

Pivot-Turn Steering Axle Maintenance • 26-7-5

Group 26, Steer Axle

Bearing Reassembly

6. Install hub or wheel on spindle. Be careful not to

damage grease seal lip when moving the hub over the

NOTE

end of spindle and threads.

Use Grade No. 2 EP multi-purpose grease,

7. Pack cavity in hub between bearings one-half full

Clark MS-107C.

with grease.

1. Install new inner and outer bearing cups by pressing

8. Install the outer wheel bearing after it has been

into hub or wheel. Be sure cups are fully seated in

packed with grease.

bore.

9. Install bearing washer and hand tighten wheel nut.

2. Pack the bearings with grease and install the inner

bearing in the hub or wheel.

10. Rotate hub or wheel counter clockwise and torque

wheel nut to 27-31 N⋅m (20-23 ft-lb).

3. Pack cavity between bearing and grease seal half full

11. Back wheel nut up until it is loose.

with grease.

12. While turning the hub or wheel counter clockwise,

4. Install new grease seal in hub or wheel inner bore.

torque the wheel nut to 2.3-2.8 N⋅m (1.7-2 ft-lb).

Apply coating of grease to inside diameter of seal

lips prior to assembly, then install seal in hub or

13. Back up wheel nut to nearest slot and install new cot-

wheel bore.

ter pin. Bend cotter pin tabs.

14. Recheck for correct bearing adjustment by rotating

the wheel by hand. Wheel should rotate freely or

with only slight “drag”. Readjust bearings by adjust-

ing wheel nut as necessary to avoid binding in bear-

ings.

15. Pack the area around wheel nut with grease.

5. Carefully press or tap grease seal into place with

asoftfaced mallet until seal is seated in bottom of

bore.

26-7-6 • Pivot-Turn Steering Axle Maintenance

SM 765, Dec ’06

Group 26, Steer Axle

16. Refit O-ring on hubcap and install hubcap by tapping

10.

Recheck for correct bearing adjustment by rotating

into place with a rubber or plastic-faced hammer.

the wheel by hand. Wheel should rotate freely or

with only slight “drag”. Readjust bearings by adjust-

ing wheel nut as necessary to avoid binding in bear-

ings.

11.

Bend cotter pin tabs over.

12.

Pack the area around wheel nut with grease.

13.

Refit O-ring on hubcap if removed or replaced and

install hubcap by tapping into place with a rubber or

plastic-faced hammer.

Steer Axle Disassembly

Wheel Bearing Adjustment

IMPORTANT

The steer wheel bearings are retained and adjusted by the

wheel nut.

Before removing any component for over-

haul, make sure the correct repair parts,

NOTE

seals, and gasket sets are available.

You should clean and repack the wheel bear-

ings before performing a wheel bearing

adjustment. See “Wheel Bearing Lubrica-

CAUTION

tion” in this Section for the complete proce-

SAFE PARKING. REFER TO PAGE 3.

dure.

NOTE

Cleanliness is of extreme importance in the

! CAUTION

repair and overhaul of this assembly.

SAFE PARKING. REFER TO PAGE 3.

• Before starting disassembly, thoroughly clean the

Make sure the truck is parked on a level, hard sur-

axle assembly of all accumulations of dirt, oil, cor-

face, the upright is fully lowered, the drive wheels

rosion, and other substances to prevent contamina-

are chocked, and the steer wheels are jacked and

tion of the parts during disassembly and overhaul.

blocked securely. Refer to “Lifting, Jacking, and

• Work in a clean area.

Blocking” for safe procedures.

• Keep all parts in order as disassembly progresses.

Remove hubcap.

Take care to properly identify each part and its

Remove and discard cotter pin.

order of removal. If necessary, keep notes and put

markings on parts using a non-destructive marker

Loosen wheel nut.

such as a grease pencil or felt-tipped pen.

After wheel nut is loosened, hit the top of wheel to

• If necessary, see Section 3, “Steer Axle Removal

loosen the bearings. This moves the bearings free of

and Replacement,” for the procedures to remove

their seated, running position.

the steer axle from the truck.

Rotate hub or wheel counter clockwise and torque

• See Section 5, “Steer Cylinder Removal and

wheel nut to 27-31 N⋅m (20-23 ft-lb).

Replacement,” for the procedures to remove the

steering cylinder and steering links from the steer

Back wheel nut up until it is loose.

axle.

While turning the hub or wheel counter clockwise,

• See Section 6, “Steering Cylinder Overhaul,” to

torque the wheel nut to 2.3-2.8 N⋅m (1.7-2 ft-lb).

disassemble the steer cylinder.

Back up wheel nut to nearest castellation slot and

install new cotter pin.

SM 765, Dec ’06

Pivot-Turn Steering Axle Maintenance • 26-7-7

Group 26, Steer Axle

To disassemble the steering knuckle, kingpin, and bearing

5. Remove the knuckle bearing washers, dust covers,

from the steer axle, it is not necessary to remove the axle

upper and lower grease seals and bearings from the

from the truck.

assembly.

1. Remove the cotter pin and washer from the bottom of

the steering link pin and remove the pin. Steering

Spacer

link is free to be removed from the cylinder rod and

knuckle.

Grease Seals

Bearing

Steering Link Pin

Cylinder Rod

Steering Link

Bearing cups may be removed by hand, by using a bearing

puller, or by tapping out using a brass drift pin.

Cotter Pin

2. Remove the stop bolts from the steering knuckle.

3. Remove the bearing protection covers which lie over

and under the steering knuckle. Don’t remove the

bearing cap.

Bearing Cover

4. Drive the kingpin down and out of the assembly.

Remove the steering knuckle. Note right and left

knuckle parts.

IMPORTANT

Do not let the knuckle or pin fall when the

pin is removed.

26-7-8 • Pivot-Turn Steering Axle Maintenance

SM 765, Dec ’06

Group 26, Steer Axle

Put the King pin on the steering axle/knuckle bore.

Parts Inspection

Tighten the stop bolt to the center hole of the King

1. Clean all bearings, cups, seals, pins, and other parts

pin.

in an approved cleaning fluid.

IMPORTANT

2. Inspect all parts for scratches, chips and wear. Check

Make sure that retainer pin enters the hole in

the steering arms of the knuckles to be sure they are

the underside of the axle

not bent or twisted. Check all threaded parts for dam-

age.

Bearing Cover

3. Replace all parts which show damage.

4. If parts are to be left exposed, coat all mating sur-

faces of parts with a light coating of engine oil.

Center Hole

Steer Axle Reassembly

Recommended greasing procedure:

a. Use Grade No. 2 EP multi-purpose grease, Clark

MS-107 or equivalent.

b. Pack all tapered roller bearings with grease

before assembly.

c. Pack knuckle pin (bearing) seals with grease

before assembly.

d. Fill steer link sockets with grease through grease

Adjust the height of steering knuckle by use of shim,

fittings after axle is assembled.

so that the steering knuckle can be slightly rotated.

Tighten the bearing protection covers above and

1. Install the bearing cup to the axle housing bore. Tap

under the axle housing.

into place with a brass drift pin or equivalent.

Replace steering link pin and snap ring to join the

Spacer

cylinder rod to the steering link and knuckle.

Axle Housing

Grease Seals

Steering Link Pin

Bearing

Cylinder Rod

Steering Link

Cotter Pin

IMPORTANT

Make sure that bearing cup is fully seated

against the shoulder in bore. There must be

no gap left between cup and the shoulder in

the bore at assembly.

2. Apply grease to upper and lower knuckle bearings

and install bearings, grease seals, and washers to

bores of axle housing.

SM 765, Dec ’06

Pivot-Turn Steering Axle Maintenance • 26-7-9

Group 29, Hydraulic Sump, Filters, and Pump

The hydraulic sump is located in the rear side compart-

Specifications

ment of the truck frame. The sump is equipped with a suc-

Hydraulic Pump Type: IntegraI gear-type pump and motor

tion line screen, return line filter, filter cap/breather.

assembly.

The hydraulic pump and motor assembly is mounted to

Sump Capacity: Usable oil = 24 Litres (6.3 Gal)

the flow plate.

Hydraulic Fluid Type: Clark Hydraulic Fluid MS-68 (or

The hydraulic pump draws oil from the sump and sends

other specification MS-68).

oil to main valve.

Filter Type: Disposable, 25 micron, return line oil filter,

The oil which was supplied from the main valve to the

100 mesh suction line screen and a 10 micron filter cap/

steering unit and attachment returns to sump.

breather filter.

Serviceable items are the pump, motor, suction line screen

and the return line filter. Other components, such as hoses,

Service Intervals

fittings, and clamps, are nonserviceable and should be

replaced if worn or damaged.

Hydraulic Fluid Level Checks: Every 8-10 hours or daily.

Hydraulic Fluid Change (Drain and Refill): Every 2000

hours of operation or every year.

Hydraulic Fluid Filter Replacement: After the first 50

hours of operation, then every year or 2000 hours of oper-

ation.

Description

NOTE

Se group 30 for a description of the complete

hydraulic circuit.

Sump Breather Cap

Return line Filter

29-1-2 • Main Hydraulic Sump, Filters, and Pump Specifications and Description

SM 765, Nov ’06

Group 29, Hydraulic Sump, Filters, and Pump

Hydraulic Fluid and Filter Change

Disconnect drain line from truck.

NOTICE

! CAUTION

If old oil is excessively dirty or hydraulic sys-

tem is contaminated, it is recommended that

SAFE PARKING. Before working on truck:

the sump tank be completely drained by

1. Park truck on a hard, level, and solid

removing the pump suction line from the

surface, such as a concrete floor with no

sump outlet and flushed withy clean oil.

gaps or breaks.

2. Put upright in vertical position and fully

Remove, clean and replace the strainer.

lower the forks or attachment.

3. Put all controls in neutral. Turn key

switch OFF and remove key.

4. Apply the parking brake and block the

wheels.

There is drain plug in the hydraulic sump tank. When the

sump tank must be drained of all fluid, the procedure is to

remove the drain plug and allow the fluid to drain into a

suitable drain pan. Unless the sump tank is to be removed

for other repair or maintenance, the hydraulic fluid can

also be changed by one of the following methods:

Pressure gauge to the diagnostic check port fitting.

NOTE: Use quick-disconnect adapter fitting.

You will need a drain pan of 24 L (6.3 gal) minimum

capacity. Be sure the outlet end of the drain line is directed

into the drain pan and held from moving when pressur-

ized.

Remove and discard old oil filter. Install new filter. Follow

the installation instructions printed on the filter body.

Turn key switch ON.

Move tilt control lever to the back tilt position to start the

lift pump. Hold tilt lever in this position until sump tank is

emptied. A steady stream of used oil should flow from the

drain line.

Continue operation until the sump tank is emptied. This

point will be reached when the pump starts to cavitate.

When cavitation occurs the pump speed will increase and

the speed sound will whine. Release the tilt lever immedi-

ately when pump cavitation occurs.

IMPORTANT

Be careful when sump is nearly emptied and

oil flow becomes erratic as the pump

approaches cavitation Do not operate pump

after cavitation occurs.

Turn the key switch OFF.

SM 765, Nov ’06

Main Hydraulic Sump, Filters, and Pump Specifications and Description • 29-1-5

Group 29, Hydraulic Sump, Filters, and Pump

The following is a list of problems and solutions relating

Pump Not Developing Sufficient

to the main hydraulic pump and associated components.

Pressure

For other hydraulic system troubleshooting, refer to

Groups 30 and 34.

•

Leak in hydraulic control system; check system for

and correct leaks.

Noisy Pump

•

Inlet line restriction; check for foreign material or

line kinks, check and clean sump suction screen.

• Hydraulic fluid level low; measure and correct

•

Suction screen dirty; clean screen.

fluid level.

•

Defective hydraulic pump; continue other trouble-

• Fluid viscosity too high; change to specified fluid.

shooting items, then consider servicing or replac-

• Sump strainer dirty; check and clean.

ing pump.

• Air leak at pump inlet line; check plumbing tight-

ness.

Pump Output Low

• Inlet line restriction; check for foreign material or

line kinks, check and clean sump suction screen.

•

Cavitating pump; see “Noisy Pump.”

• Air leak at pump shaft packing; replace packing.

•

Air in fluid or wrong fluid; drain and fill with cor-

rect fluid.

• Defective hydraulic pump; continue other trouble-

shooting items, then consider servicing or replac-

•

System relief valve set too low or too high, stuck or

ing pump.

leaking; correct relief valve, pump may be OK.

•

Overheated fluid; see “Overheated Pump and/or

Fluid.”

Pump Not Delivering Hydraulic Fluid

•

Contaminated fluid; eliminate contamination

• Hydraulic fluid level low; check and correct fluid

source and replace fluid.

level.

•

Gear face, body or cover nicked; repair or replace

• Sump suction screen dirty; check and clean.

pump.

• Inlet line restriction; check for foreign material or

•

Excessive side loading, wear plate tight in body

line kinks, check and clean sump suction screen.

bore, pinched thrust plate; inspect and service

• Air leak in suction line: check plumbing tightness.

pump.

• Fluid viscosity too high: check fluid viscosity and

change to specified fluid.

Foaming Fluid

• Defective hydraulic pump; continue other trouble-

•

Cavitating pump; see “Noisy Pump.”

shooting items, then consider servicing or replac-

ing pump.

•

Wrong fluid; drain and fill with correct fluid.

Failure to Build Pressure

Overheated Pump and/or Fluid

• Hydraulic fluid level low; measure and correct

• Low viscosity fluid; drain and fill with correct

fluid level.

fluid.

• Defective relief valve or pump: perform pressure

• Contaminated fluid; drain fluid, clean suction

check to test valve and pump.

screen, replace filter and fill sump.

• Cavitating pump: see “Noisy Pump.”

• Pump drive shaft misaligned; check mounting and

alignment.

• Axial loading on drive shaft; check shaft end clear-

ance and shaft alignment; check for worn key/

spline.

• Relief valve usually in bypass; check relief setting.

29-2-2 • Main Hydraulic Pump Troubleshooting

SM 765, Nov ’06

Group 29, Hydraulic Sump, Filters, and Pump

Main Hydraulic Pump Removal

NOTE

Capacity of hydraulic sump is 24 L (6.3 gal).

! CAUTION

1. Place a drip pan under the hydraulic pump for oil that

SAFE PARKING. Before working on truck:

will drain from the pump and hoses when they are

disconnected.

1. Park truck on a hard, level and solid sur-

face, such as a concrete floor with no

2. Disconnect suction line from pump and plug the line.

gaps or breaks.

2. Put upright in vertical position and fully

lower the forks or attachment.

3. Put ail controls in neutral. Turn key

switch OFF and remove key.

4. Disconnect the battery.

5. Apply the park brake and block the

Pump Suction Line

wheels.

The main hydraulic pump is located beneath the flow

plate. The pump can be removed from the truck without

removing the pump and motor assembly.

Serviceable items are the pump, motor and the suction

line filter. Other components such as hoses, fittings and

clamps are non-serviceable and should be replaced if

faulty.

Control Valve

Filter

Steering Gear

Pump

29-3-2 • Main Hydraulic Removal and Installation

SM 765, Sep ’06

Group 29, Hydraulic Sump, Filters, and Pump

3. Disconnect the pressure line from the pump. Cap the

4. Connect pump outlet hose and tighten. Use two

hose and set aside.

wrenches to tighten hose fittings to prevent twisting

of lines.

NOTE

Always clean or replace hydraulic sump suc-

tion screen fitting when installing new or

Pressure Line

rebuilt pump. See Section 1, Main Hydraulic

Filters and Fluid Maintenance.

Hydraulic

5. Refill sump as necessary using Clark Specification

Pump

MS-68 hydraulic fluid. See Section 1 for description

Hydraulic Motor

of sump tank fill levels.

6. Reinstall hose and cable support bracket.

7. Check operation of hydraulic system. See Section 1,

Main Hydraulic Filters and Fluid Maintenance.

8. Check fluid level of sump again. Add fluid as neces-

sary.

4. Remove the pump mounting fasteners.The ground

strap will come off with the fasteners.

Routine Maintenance

• No maintenance is necessary other than periodic

checks for tightness of the mounting bolts and port

Hydraulic Motor

Hydraulic

fittings plus visual examination for oil leaks. The

Pump

unit should be kept externally clean.

• The unit must be operated on clean hydraulic fluid.

Directions for filter service in this Group must be

adhered to. A fluid cleanliness level of IS04406 17/

14 or better is recommended to give maximum life.

Main Hydraulic Pump Installation

IMPORTANT

Keep all components clean during installa-

tion.

1. Be sure new or serviced pump is well lubricated

before installation.

2. Install pump onto motor. Install and tighten cap-

screws.

3. Slide suction hose and clamp into place and tighten.

SM 765, Sep ’06

Main Hydraulic Removal and Installation • 29-3-3

Group 30, Hydraulic Control Valve/Lift Circuit

Section 1

Hydraulic Control Valve/Lift Circuit

Specifications and Description

Specifications

Hydraulic Fluid Type: Clark specification MS-68 (Clark

Service Intervals

part #1802155 and #1800236)

Hydraulic System Relief Pressure Check: Every year or

Main Relief Valve Setting: 20.6 to 21.1 MPa (2988 to

every 2000 hours of operation.

3060 psi) at rated flow.

Auxiliary Relief Valve Setting: 13.7 to 14.2 kPa (1987 to

2060 psi) at rated flow.

Rated Flow: 76 L/min (20 gpm).

Maximum Pressure Drop at Rated Flow:

Inlet to outlet: 689 kPa (100 psi).

Lift spool (spool #l):

- Inlet to cylinder port: 689 kPa (100 psi)

- Cylinder port to outlet: 550 kPa (80 psi).

Tilt spool (spool #2):

- Inlet to cylinder port: 689 kPa (100 psi)

- Cylinder port to outlet: 550 kPa (80 psi).

Auxiliary spools (spools #3 and #4):

- Inlet to cylinder port: 345 kPa (50 psi)

- Cylinder port to outlet: 207 kPa (30 psi).

SM 765, Nov ’06

Hydraulic Control Valve/Lift Circuit Specifications and Description • 30-1-1

Group 30, Hydraulic Control Valve/Lift Circuit

moved. Excess oil flow is returned to the sump. A check

Description

valve prevents reverse flow.

The following description focuses primarily on hydraulic

When all the control valve spools are in neutral, the micro

circuitry controlled by the main hydraulic control valve,

switch turns the pump motor OFF and not fluid flows.

that is, the lift/tilt/aux circuit. Various other hydraulic sys-

When a spool is partially shifted and the associated cylin-

tems come into play, however, and are mentioned. The

der or other actuator has not reached its end-of-travel,

entire hydraulic system is depicted in the schematics in

some of the fluid flows to the cylinder (actuator) and the rest

Section 2 (next page).

flows to the sump line. In both cases, the pressure in the system

Descriptions of the braking and steering circuits are given

should be less than the amount required to open the relief valves.

in Groups 23 and 25.

The main relief valve vents flow to the sump when one of

The main hydraulic pump (described in Group 29) is

the following conditions is present:

driven by the pump motor and draws fluid from the sump

• The operator continues to hold the lift control in

through a particle-blocking suction screen.

the lift position after the lift mechanism reaches its

The main hydraulic control valve features an open-center,

endof-travel.

parallel-circuit type modular design. It has the main (lift/

• Too heavy a load is being lifted.

tilt) pressure relief valve (steering pressure relief valve

• The operator continues to hold the tilt control in

located in the steering control assembly (Orbitrol)), a sec-

the tilt position after the tilt mechanism has

ondary pressure relief valve for optional auxiliary compo-

reached its end-of-travel (This is called “tilt

nents, a lift spool, a tilt spool with an integral

bypass.“)

counterbalance valve, optional auxiliary spools, and

• Auxiliary relief fails to operate.

adjustable pressure-compensated flow controls. All spools

are low-leakage design.

The auxiliary relief valve vents flow to the sump when the

operator continues to hold the attachment control in the

The main hydraulic valve has from two to four valve sec-

operated position after the attachment reaches its end-of-

tions. Each section performs a separate function; standard

travel.

two spool assemblies have a inlet/lift section (with fluid

inlet port), a tilt section, and an outlet section. A third and

Main and auxiliary relief pressure settings can be checked

fourth section may be added to control auxiliary compo-

through a gauge port on the main valve.

nents.

A tilt-lock valve built into the main control valve assem-

When lift attachments are used, an auxiliary section may

bly locks the upright into its current tilt position when the

be added to the outer (RH) side of the standard (lift/tilt

truck is turned off. A load lowering flow valve mounted

only) main valve. The optional auxiliary sections also

on the upright limits the speed at which the operator can

have an adjustable relief valve and can be assembled with

lower a load, decreasing the speed for heavier loads. A

optional flow control levels.

velocity fuse built into one of the lift cylinder ports pre-

vents the upright from falling rapidly should a hydraulic

The valve spools are arranged in standard sequence (from

line rupture or be disconnected.

the operator’s position) to first provide lift control, then

tilt, and finally auxiliary control. The control levers are

spring-loaded (by the valve spool centering springs) to

return them to neutral when released. Oil flow is con-

trolled by the amount or distance the control handles are

NOTE

Hydraulic plumbing arrangement is illustrated in Group 29.

30-1-2 • Hydraulic Control Valve/Lift Circuit Specifications and Description

SM 765, Nov ’06

Group 30, Hydraulic Control Valve/Lift Circuit

Section 3

Hydraulic System Troubleshooting

The following is a list of problems and solutions relating

• Cavitating pump; check hydraulic plumbing for

to the main hydraulic control valve and associated compo-

airtight hoses and connections.

nents. For other hydraulic system troubleshooting, refer to

• Pump driveshaft misaligned; check mounting and

Groups 29 and 34.

alignment.

No lift, tilt, or auxiliary function

• Axial loading on drive shaft; check shaft end clear-

ance and shaft alignment; check for worn key/

• Hydraulic fluid very low; check and fill to correct

spline.

level.

• Relief valve in bypass; check relief setting.

• Hose or fittings broken; replace component.

• Defective main lift valve; check other Trouble-

Load cannot be lifted to maximum height

shooting items for possible cause, then consider

rebuilding or replacing main lift valve.

• Hydraulic fluid low: check and fill to correct level.

• Hydraulic pump defective: check other Trouble-

• Hydraulic pump defective; check other Trouble-

shooting items for possible cause, then consider

rebuilding or replacing pump.

No motion, slow or jerky action of

Oil leaks at top of lift (secondary) cylinder(s)

hydraulic system

• Plugged vent line; check and clear line.

• Spool not moved to full stroke; check travel and

• Worn or damaged piston seal: rebuild cylinder.

linkage adjustment.

• Scored cylinder wall; replace cylinder.

• Relief valve not properly set, stuck in place, and/or

See Group

34, “Cylinder Removal, Overhaul, and

worn; check and clean valve, replace if necessary.

Replacement.”

• Dirt or foreign particles lodged between relief

valve control poppet and seat: check valve and

Oil leak at tilt or auxiliary function cylinder

clean.

• Worn or damaged seal; rebuild cylinder.

• Valve body cracked inside; check and replace

entire valve.

• Scored piston rod; repair or replace rod.

See Group

34, “Cylinder Removal, Overhaul, and

Foaming hydraulic fluid

Replacement.”

• Low oil level; check and fill to correct level.

Load will not hold

• Wrong fluid; drain and refill with correct oil.

• Oil too heavy; change to correct viscosity.

• .Oil bypassing between lift spool and valve body; over-

• Pump inlet line restriction or line kinked; clean line

haul valve and spool.

and suction screen or repair kinked hose.

• Spool not centered; see spool remedies for correct-

• Hydraulic pump cavitating (pumping air with

ing problems when spools do not return to neutral.

fluid); check hydraulic plumbing for airtight hoses

• Oil bypassing piston in cylinder; repair or replace

and connections.

cylinder.

Overheated hydraulic fluid

Oil leaks at either end of main hydraulic

• Thin fluid; drain and fill with correct fluid.

valve spool

• Fluid contaminated; drain sump, clean suction

• Defective O-ring seals; rebuild valve.

screen, replace filter, and refill.

SM 765, Sep ’06

Hydraulic System Troubleshooting • 30-3-1

Group 30, Hydraulic Control Valve/Lift Circuit

Spring-centered spools do not return to

No relief valve action (high pressure)

neutral

• Small particles of dirt in relief valve subassembly;

check, clean, and/or replace relief valve, clean

• Broken springs; rebuild valve.

hole.

• Entrapped foreign particles; check and clean sys-

• Relief valve subassembly installed backwards;

tem and valve.

reinstall correctly.

• Bent spool; replace with new valve section.

• Misalignment or binding of linkage; check and

Load drops when spool is moved from

align/adjust linkage.

neutral to lift position

• Dirt or foreign particles lodged between check

valve ball and seat; check and clean.

• Sticking or scored check valve; clean if sticking,

replace if scored, replace poppet.

30-3-2 • Hydraulic System Troubleshooting

SM 765, Nov ’06

Group 30, Hydraulic Control Valve/Lift Circuit

Section 4

Hydraulic System Pressure Checks and Adjustments

! CAUTION

SAFE PARKING. Before working on truck:

1. Park truck on a hard, level, and solid

surface, such as a concrete floor with no

gaps or breaks.

2. Put upright in vertical position and fully

lower the forks or attachment.

3. Put all controls in neutral. Turn key

switch OFF and remove key.

4. Apply the parking brake and block the

wheels.

Remove the cap from the gauge port on the valve and

connect pressure gauge to the fitting.

Relief Pressure Checks

Following is the procedure for checking main hydraulic

valve lift pressure and auxiliary relief pressure (if the

truck is equipped with an auxiliary component).

Hydraulic system relief pressure setting may be checked

using a Mica Quadrigage (Clark Part No. 923770) or with

a conventional pressure gauge with suitable pressure

range calibration. To cover all models of the truck, a

gauge with capacity range of 0 to 34,475 kPa minimum (0

to 5000 psi) is recommended.

! WARNING

HYDRAULIC FLUID SAFETY. Keep all

NOTE

hydraulic ports and components clean. Wipe

Use quick-disconnect adapter fitting, Clark

the area on the pump around the diagnostic

Part #913125.

check port completely clean to prevent any

Check main relief pressure: Turn key switch on,

contamination from entering the hydraulic

system.

move the lift control lever to full back lift relief posi-

tion. Hold lift control in relief position until pressure

When checking the hydraulic system, do not

reading is obtained, and then release. Gauge should

use your hands to check for leakage. Use a

piece of cardboard or paper to search for

read 20,600 to 21,100 kPa (3988 to 3060 psi).

leaks. Escaping fluid under pressure can pen-

IMPORTANT

etrate the skin causing serious injury. Relieve

Do not operate system in relief any longer

pressure before disconnecting hydraulic or

than required to read the pressure gauge.

other lines. Tighten all connections before

applying pressure. Keep hands and body

Check auxiliary relief pressure: (Truck must have

away from pinholes and nozzles which eject

auxiliary component and auxiliary section added to

fluids under high pressure.

main hydraulic valve.) Move the auxiliary control

1. Remove the covers enclosing the main hydraulic

lever to full back or forward relief position. Hold

auxiliary control in relief position until pressure

valve to access the hydraulic system pressure diag-

reading is obtained, and then release. Gauge should

nostic check port.

read 13,700 to 14,200 kPa (1987 to 2060 psi).

SM 765, Nov '06

Hydraulic System Pressure Checks and Adjustments • 30-4-1

Group 30, Hydraulic Control Valve/Lift Circuit

Main Pressure Relief Adjustment

Auxiliary Pressure Relief Adjustment

IMPORTANT

Main pressure relief setting is set at the fac-

The auxiliary relief setting only applies to a

tory. If the relief pressure does not measure

hydraulic valve that has auxiliary sections

within the setting range, main pressure relief

added.

setting is adjusted.

To adjust the hydraulic system auxiliary pressure relief

To adjust the hydraulic system main pressure relief valve:

valve:

1. Loosen the jam nut on the main relief valve adjust-

1. Loosen the jam nut on the auxiliary relief valve

ment screw.

adjustment screw.

Pressure

check port

Secondary

relief valve

Main

relief valve

Jam nut

Adjustement screw

2. Turn the adjustment screw to set the main pressure

2. Turn the adjustment screw to set the auxiliary pres-

relief setting to the normal range.

sure relief setting to the normal range.

3. Reset the jam nut on the main relief valve adjustment

3. Reset the jam nut on the auxiliary relief valve adjust-

screw.

ment screw.

30-4-2 • Hydraulic System Pressure Checks and Adjustments

SM 765, Nov ’06

Group 30, Hydraulic Control Valve/Lift Circuit

GEX 30

Flowrate per RPM

Lift

Tilt in

GEX 20/25

Flowrate

Speed

velocity

RPM

Remark

Lift

Tilt in

mm/

deg/

Flowrate

lpm

gpm

Speed

velocity

sec

RPM

Remark

mm/

deg/

500

8.0

2.1

19.29

3.10

lpm

gpm

sec

600

9.8

2.6

23.63

3.80

500

9.7

2.6

23.39

3.76

700

11.6

3.1

27.97

4.50

600

11.8

3.1

100

28.45

4.57

800

13.4

3.6

114

32.31

5.19

700

14.0

3.7

118

33.76

5.43

900

15.2

4.0

129

36.65

5.89

800

16.1

4.3

137

38.82

6.24

1000

17.1

4.5

145

41.24

6.63

900

18.2

4.8

155

43.89

7.05

1100

18.9

5.0

160

45.58

7.32

1000

20.4

5.4

173

49.19

7.91

1200

20.7

5.5

175

49.92

8.02

1100

22.5

5.9

191

54.26

8.72

1300

22.5

5.9

191

54.26

8.72

1200

24.7

6.5

209

59.56

9.57

1400

24.3

6.4

206

58.60

9.42

1300

26.8

7.1

227

64.63

10.39

1500

26.1

6.9

221

62.94

10.12

1400

28.9

7.6

245

69.69

11.20

1600

27.9

7.4

236

67.28

10.81

1500

31.1

8.2

263

75.00

12.05

1700

29.7

7.8

252

71.62

11.51

1600

33.2

8.8

282

80.06

12.87

1800

31.5

8.3

267

75.96

12.21

1700

35.3

9.3

300

85.12

13.68

1900

33.3

8.8

282

80.30

12.91

1800

37.5

9.9

318

90.43

14.53

2000

35.1

9.3

298

84.64

13.60

1900

39.6

10.5

336

2100

36.9

9.8

313

88.98

14.30

2000

41.8

11.0

354

2200

38.7

10.2

328

2100

43.9

11.6

372

2300

40.5

10.7

344

2200

46.0

12.2

390

2400

42.3

11.2

359

2300

48.2

12.7

408

2500

44.1

11.7

374

2400

50.3

13.3

427

2600

45.9

12.1

389

2500

52.4

13.9

445

2700

47.7

12.6

405

2600

54.6

14.4

463

2800

49.5

13.1

420

2700

56.7

15.0

481

2900

47.7

13.6

435

2800

58.9

15.5

499

3000

53.2

14.0

451

2900

61.0

16.1

517

3100

101

55.0

14.5

466

3000

63.1

16.7

535

3200

105

56.8

15.0

481

3100

101

65.3

17.2

553

3300

108

58.6

15.5

497

3200

105

67.4

17.8

572

3400

111

60.4

15.9

512

3300

108

69.5

18.4

590

3500

115

62.2

16.4

527

3400

111

71.7

18.9

608

3500

115

73.8

19.5

626

* The above are only theoretical value.

• Displacement of pump : 19 cc/rev

* The above are only theoretical value.

• Volumetric efficiency of pump : 0.95

• Displacement of pump : 22.5 cc/rev

• Volumetric efficiency of pump : 0.95

SM 765, Nov ’06

Hydraulic System Pressure Checks and Adjustments • 30-4-3

Group 30, Hydraulic Control Valve/Lift Circuit

Hydraulic Control Valve Removal

Control Valve Linkage Disassembly

IMPORTANT

Remove the cotter rings and clevis pins connecting the lift

Keep all hydraulic ports, components, and

and tilt (and auxiliary, as applicable) lever rods from the

fittings completely clean during valve

hydraulic valve spools.

removal and replacement to prevent any con-

tamination from entering the hydraulic sys-

tem.

Preparation for Valve Removal

1. Park truck in a safe position and fully lower the

upright.

2. Return all controls to neutral, apply the parking

brake, and turn key switch OFF.

3. Move all hydraulic control levers to all working posi-

tions and return them to neutral. Be sure there is no

Clevis Pin

hydraulic pressure applied to the system by attach-

ments.

Cotter Pin

Valve Spool

4. Remove floor plate.

5. Remove the right cowl cover from under the dash in

the operator’s compartment. See removal and

Valve Removal

replacement procedures in Group 38.

1. Remove the three hex capscrews mounting the

6. Air clean the hydraulic valve and fittings.

hydraulic valve to the hydraulic valve mounting

bracket .

7. Place a drain pan under the truck and loosen and

remove all hydraulic lines from the valve. Plug the

valve ports. Mark or tag each line as removed to

Hydraulic Valve mounting

Bracket

assure correct position of line at assembly.

Tilt Cylinder

Lines

To upringt

Feed Line

from Pump

Return Line

to Sump

2. Remove valve assembly from valve mounting

bracket. See Section 6 for valve overhaul instruc-

tions.

NOTE

Be sure to clean up any oil spills and dry the

floor to prevent accidents.

8. Cap ends of lines to keep them clean. Tie ends of

lines to truck to prevent loose ends dropping and

leaking oil onto floor

30-5-2 • Hydraulic Control Valve Removal and Replacement

SM 765, Sep ’06

Clark GEX20-30 (RATED CAPACITY : 2000~3000kg). SERVICE MANUAL (2006) - page 3