Range Rover. Manual - part 152

ZF AUTO

DESCRIPTION AND OPERATION

Torque converter housing

On 2.5 litre Diesel models a 260 mm (10.2 in)
diameter torque converter is used. On 4.0 and 4.6 litre
petrol models a 280 mm (11 in) diameter torque
converter is used. On 4.6 litre petrol models up to
99MY the torque converter is longer than the torque
converter used on 4.0 litre petrol models. From 99MY,
both the 4.0 and 4.6 litre petrol models use the shorter
torque converter previously used on up to 99MY 4.0
litre models.

The torque converter housing attaches the gearbox to
the engine and contains the torque converter. The
torque converter is connected to the engine drive
plate and transmits the drive from the engine to the
gearbox input shaft. When engaged, a hydraulic
lock-up clutch in the torque converter prevents
slippage, to give a direct drive from the engine to the
gearbox for improved efficiency.

Intermediate plate

The intermediate plate supports the gearbox input
shaft and provides the interface between the
transmission fluid pump and the lubrication circuit.
The pump attaches to the front of the intermediate
plate and is driven by an impeller in the torque
converter. The pump pressurises transmission fluid
drawn from the sump on the gearbox housing. The
pressurised fluid then circulates through the torque
converter and gearbox housing components for
cooling, lubrication and gear shift purposes. Ports
around the outer periphery of the intermediate plate
provide the inlet and outlet connections to the fluid
cooler and a pressure take-off point for servicing.

On ZF4HP24 gearboxes, the intermediate plate is
15 mm (0.6 in) thicker than fitted to the ZF4HP22
gearbox to accomodate a larger fluid pump unit. To
compensate for the increased length of the
intermediate plate, the rear extension housing is
15 mm (0.6 in) shorter than that fitted to the ZF4HP22
gearbox.

Gearbox housing

The gearbox housing contains two epicyclic gear sets
on input and output shafts. Hydraulic clutches on the
shafts control which elements of the gear sets are
engaged, and their direction of rotation, to produce the
P and N selections, four forward gear ratios and one
reverse gear ratio.

Gear ratios

Gear

Ratio

1st

2.480:1

2nd

1.480:1

3rd

1.000:1

4th

0.728:1

Reverse

2.086:1

The lock-up and brake clutches are operated by
pressurised transmission fluid from the valve block in
the sump. A manual valve and four solenoid valves,
also known as Motorised Valves (MV), control the
supply of pressurised transmission fluid from the valve
block:

•

The manual valve controls the fluid supply for P,
R, N and D selector positions. The four solenoid
valves operate accordingly to operate shift
control, lock-up and shift quality.

•

Solenoid valves MV 1 and MV 2 control the
supplies that operate the brake clutches for shift
control. They are also used to prevent accidental
engagement of reverse when moving forwards
and a forward gear when moving backwards.

•

Solenoid valve MV 3 controls the supply that
operates the lock-up clutch.

•

Solenoid valve MV 4 modulates the pressure of
the supplies to the brake clutches, to control shift
quality.

Operation of the manual valve is controlled by the
selector lever assembly. In the gearbox, a selector
shaft engages with the manual valve. The selector
shaft is connected to the selector lever assembly via
the selector cable and a selector lever on the left side
of the gearbox. The selector shaft also operates a
mechanism that locks the output shaft when P is
selected.

Operation of the solenoid valves is controlled by the
EAT ECU.

AUTOMATIC GEARBOX

NEW RANGE ROVER

DESCRIPTION AND OPERATION

An output shaft speed sensor in the gearbox housing
outputs a signal to the EAT ECU. The EAT ECU
compares output shaft speed with engine speed to
determine the engaged gear and output shaft speed
with vehicle speed to confirm the range selected on
the transfer box. The speed sensor signal is a
diagnostic function and not essential for correct
gearbox operation.

A bayonet lock electrical connector in the gearbox
casing, to the rear of the selector lever, connects the
solenoid valves and the output shaft speed sensor to
the vehicle wiring.

A pressed steel sump encloses the valve block and
collects transmission fluid draining from the gearbox
housing. A suction pipe and filter on the underside of
the valve block connect to the inlet side of the fluid
pump. A magnet is installed in the sump to collect any
magnetic particles that may be present. A level plug
and a drain plug are installed in the sump for
servicing.

Rear extension housing

The rear extension housing provides the interface
between the gearbox housing and the transfer box. A
splined output shaft transmits the drive from the
gearbox to the transfer box. A seal in the rear of the
housing prevents leakage past the extension shaft. A
breather pipe, attached to the left side of the rear
extension housing, ventilates the interior of the
gearbox and rear extension housings to atmosphere.
The open end of the breather pipe is located in the
engine compartment at the right rear corner of the
engine, against the bulkhead. On 99MY V8 vehicles,
the breather pipe is also located against the bulkhead,
but the open end is routed down the bulkhead and
located below the converter housing.

Gearbox power flows

The following schematics show the power flow
through the gearbox for each forward gear when D is
selected, and for reverse. The key to the Item
numbers on the schematics, and in parenthesis in the
accompanying text, can be found on the illustration
’Sectioned view of gearbox’ shown earlier in this
section of the Workshop Manual.

1st Gear (D selected)

Clutches (4) and (11) are engaged. The front planet gear carrier of gear set (9) locks against the gearbox housing
through freewheel (15) when the engine powers the vehicle, and freewheels when the vehicle is coasting. Gear
set (10) rotates as a solid unit with the front planet gear carrier.

ZF AUTO

DESCRIPTION AND OPERATION

2nd Gear (D selected)

Clutches (4), (6), (7) and (11) are engaged. Freewheel (15) overruns. The hollow shaft with the sun wheel of gear
set (9) is locked. Gear set (10) also rotates as a solid unit.

3rd Gear (D selected)

Clutches (4), (5), (7) and (11) are engaged. Freewheels (15) and (16) are overrun. Gear sets (9) and (10) rotate as
a solid unit.

4th Gear (D selected)

Clutches (4), (5), (7) and (12) are engaged. Freewheels (14), (15) and (16) are overrun. Gear set (9) rotates as a
solid unit. The hollow shaft with the sun wheel of gear set (10) is locked.

AUTOMATIC GEARBOX

NEW RANGE ROVER

DESCRIPTION AND OPERATION

Reverse gear

Clutches (5), (8) and (11) are engaged. Freewheels (14) and (16) are overrun. The front planet gear carrier of gear
set (9) is locked. Gear set (10) also rotates as a solid block.

Gear position switch

The gear position switch outputs signals that are
related to the position of the selector lever assembly.
The switch is installed on the selector shaft on the left
side of the gearbox. Slotted mounting holes allow the
switch to be turned relative to the shaft for adjustment.
A fly lead connects the switch to the vehicle wiring.

Movement of the selector lever assembly turns the
selector shaft, which connects with three sliding
contacts in the switch. The contacts are identified as
the X, Y and Z. When closed:

•

The X, Y and Z contacts output a combination of
earth signals to the EAT ECU as shown in the
table below.

•

The outputs of the X, Y and Z contacts are
monitored by the EAT ECU, ECM and the BeCM
to determine the position of the selector lever
assembly.

The signals are interpreted by the EAT ECU for the
correct gear selection. The ECM uses the signals to
control engine idle speed etc. The BeCM uses the
signals to illuminate the gear selection display on the
selector cover, operate the reverse lamps, wiper
reverse operation and message centre display etc.

Gear position switch X, Y, Z outputs

Position switch

ECU pin

Line 1 (X)

Line 2 (Y)

Line 3 (Z)

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