Hummer H2. Manual - part 32

BASIC CLUTCH TROUBLE SHOOTING CHART 

unique situation or individual vehicle configuration. The purpose of this Trouble 
Shooting information is to provide a list of common causes to problem 
symptoms. For model-specific Trouble Shooting, refer to SUBJECT, 
DIAGNOSTIC, or TESTING articles available in the section(s) you are accessing. 

CONDITION & POSSIBLE CAUSE 

CORRECTION 

Chattering or Grabbing 

Incorrect clutch adjustment 

Adjust clutch 

Oil, grease or glaze on facings 

Disassemble and clean or replace 

Loose "U" joint flange 

See DRIVE AXLES article 

Worn input shaft spline 

Replace input shaft 

Binding pressure plate 

Replace pressure plate 

Binding release lever 

See CLUTCH article 

Binding clutch disc hub 

Replace clutch disc 

Unequal pressure plate contact 

Replace worn/misaligned components 

Loose/bent clutch disc 

Replace clutch disc 

Incorrect transmission alignment 

Realign transmission 

Worn pressure plate, disc or flywheel 

Replace damaged components 

Broken or weak pressure springs 

Replace pressure plate 

Sticking clutch pedal 

Lubricate clutch pedal & linkage 

Incorrect clutch disc facing 

Replace clutch disc 

Engine loose in chassis 

Tighten all mounting bolts 

Failure to Release 

Oil or grease on clutch facings 

Clean or replace clutch clutch disc 

Incorrect release lever or pedal 
adjustment 

See CLUTCH article 

Worn or broken clutch facings 

Replace clutch disc 

Bent clutch disc or pressure plate 

Replace damaged components 

Clutch disc hub binding on input shaft 

Clean or replace clutch disc and/or input 

shaft 

Binding pilot bearing 

Replace pilot bearing 

Sticking release bearing sleeve 

Replace release bearing and/or sleeve 

Binding clutch cable 

See CLUTCH article 

Defective clutch master 

Replace master cylinder 

Defective clutch slave 

Replace slave cylinder 

Air in hydraulic system 

Bleed hydraulic system 

Rattling 

Weak or broken release lever spring 

Replace spring and check alignment 

Damaged pressure plate 

Replace pressure plate 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Trouble Shooting - Basic Procedures

  

Broken clutch return spring 

Replace return spring 

Worn splines on clutch disc or input 
shaft 

Replace clutch disc and/or input shaft 

Worn clutch release bearing 

Replace release bearing 

Dry or worn pilot bearing 

Lubricate or replace pilot bearing 

Unequal release lever contact 

Align or replace release lever 

Incorrect pedal free play 

Adjust free play 

Warped or damaged clutch disc 

Replace damaged components 

Slipping 

Pressure springs worn or 

Release pressure plate 

Oily, greasy or worn facings 

Clean or replace clutch disc 

Incorrect clutch alignment 

Realign clutch assembly 

Warped clutch disc or pressure plate 

Replace damaged components 

Binding release levers or clutch pedal 

Lubricate and/or replace release components 

Squeaking 

Worn or damaged release 

Replace release bearing 

Dry or worn pilot or release bearing 

Lubricate or replace assembly 

Pilot bearing turning in crankshaft 

Replace pilot bearing and/or crankshaft 

Worn input shaft bearing 

Replace bearing and seal 

Incorrect transmission alignment 

Realign transmission 

Dry release fork between pivot 

Lubricate release fork and pivot 

Heavy and/or Stiff Pedal 

Sticking release bearing sleeve 

Replace release bearing and/or sleeve 

Dry or binding clutch pedal hub 

Lubricate and align components 

Floor mat interference with pedal 

Lay mat flat in proper area 

Dry or binding ball/fork pivots 

Lubricate and align components 

Faulty clutch cable 

Replace clutch cable 

Noisy Clutch Pedal 

Faulty interlock switch 

Replace interlock switch 

Self-adjuster ratchet noise 

Lubricate or replace self-adjuster 

Speed control interlock switch 

Lubricate or replace interlock switch 

Clutch Pedal Sticks Down 

Binding clutch cable 

See CLUTCH article 

Springs weak in pressure plate 

Replace pressure plate 

Binding in clutch linkage 

Lubricate and free linkage 

Noisy 

Dry release bearing 

Lubricate or replace release bearing 

Dry or worn pilot bearing 

Lubricate or replace bearing 

Worn input shaft bearing 

Replace bearing 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Trouble Shooting - Basic Procedures

  

DRIVE AXLE - NOISE DIAGNOSIS 

Unrelated Noises 

Some driveline trouble symptoms are also common to the engine, transmission, wheel bearings, tires, and other 
parts of the vehicle. Ensure cause of trouble actually is in the drive axle before adjusting, repairing, or replacing 
any of its parts.  

Non-Drive Axle Noises 

A few conditions can sound just like drive axle noise and have to be considered in pre-diagnosis. The 4 most 
common noises are exhaust, tires, CV/universal joints and wheel trim rings.  

In certain conditions, the pitch of the exhaust gases may e gear whine. At other times, it may be mistaken for a 
wheel bearing rumble.  

Tires, especially radial and snow, can have a high-pitched tread whine or roar, similar to gear noise. Also, some 
non-standard tires with an unusual tread construction may emit a roar or whine.  

Defective CV/universal joints may cause clicking noises or excessive driveline play that can be improperly 
diagnosed as drive axle problems.  

Trim and moldings also can cause a whistling or whining noise. Ensure none of these components are causing 
the noise before disassembling the drive axle.  

Gear Noise 

A "howling" or "whining" noise from the ring and pinion gear can be caused by an improper gear pattern, gear 
damage, or improper bearing preload. It can occur at various speeds and driving conditions, or it can be 
continuous.  

Before disassembling axle to diagnose and correct gear ke sure that tires, exhaust, and vehicle trim have been 
checked as possible causes.  

Chuckle 

This is a particular rattling noise that sounds like a stick against the spokes of a spinning bicycle wheel. It 
occurs while decelerating from 40 MPH and usually can be heard until vehicle comes to a complete stop. The 
frequency varies with the speed of the vehicle. 

Transmission Click 

Weak springs in pressure 

Replace pressure plate plate 

Release fork loose on ball stud 

Replace release fork and/or ball stud 

Oil on clutch disc damper 

Replace clutch disc 

Broken spring in slave cylinder 

Replace slave cylinder 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Trouble Shooting - Basic Procedures

  

A chuckle that occurs on the driving phase is usually caused ive clearance due to differential gear wear, or by a 
damaged tooth on the coast side of the pinion or ring gear. Even a very small tooth nick or a ridge on the edge 
of a gear tooth is enough the cause the noise.  

This condition can be corrected simply by cleaning the gear tooth nick or ridge with a small grinding wheel. If 
either gear is damaged or scored badly, the gear set must be replaced. If metal has broken loose, the carrier and 
housing must be cleaned to remove particles that could cause damage.  

Knock 

This is very similar to a chuckle, though it may be louder, and occur on acceleration or deceleration. Knock can 
be caused by a gear tooth that is damaged on the drive side of the ring and pinion gears. Ring gear bolts that are 
hitting the carrier casting can cause knock. Knock can also be due to excessive end play in the axle shafts.  

Clunk 

Clunk is a metallic noise heard when an automatic transmission is engaged in Reverse or Drive, or when throttle 
is applied or released. It is caused by backlash somewhere in the driveline, but not necessarily in the axle. To 
determine whether driveline clunk is caused by the axle, check the total axle backlash as follows:  

1. Raise vehicle on a frame or twinpost hoist so that drive wheels are free. Clamp a bar between axle 

companion flange and a part of the frame or body so that flange cannot move.  

2. On conventional drive axles, lock the left wheel to keep it from turning. On all models, turn the right 

wheel slowly until it is felt to be in Drive condition. Hold a chalk marker on side of tire about 12" from 
center of wheel. Turn wheel in the opposite direction until it is again felt to be in Drive condition.  

3. Measure the length of the chalk mark, which is the total axle backlash. If backlash is one inch or less, 

drive axle is not the source of clunk noise.  

Bearing Whine 

Bearing whine is a high-pitched sound similar to a whistle. It is usually caused by malfunctioning pinion 
bearings. Pinion bearings operate at drive shaft speed. Roller wheel bearings may whine in a similar manner if 
they run completely dry of lubricant. Bearing noise will occur at all driving speeds. This distinguishes it from 
gear whine, which usually comes and goes as speed changes.  

Bearing Rumble 

Bearing rumble sounds like marbles being tumbled. It is usually caused by a malfunctioning wheel bearing. The 
lower pitch is because the wheel bearing turns at only about 1/3 of drive shaft speed.  

Chatter On Turns 

This is a condition where the entire front or rear of vehicle vibrates when vehicle is moving. The vibration is 
plainly felt as well as heard. Extra differential thrust washers installed during axle repair can cause a condition 
of partial lock-up that creates this chatter.  

Axle Shaft Noise 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Trouble Shooting - Basic Procedures