L322 Range Rover System Description and Operation
AUTOMATIC TRANSMISSION – ZF 5HP24
44-2-10 DESCRIPTION AND OPERATION
Description
General
The ZF 5HP24 transmission is an electronically controlled, five speed unit for use with the V8 petrol engine. The
transmission is manufactured by ZF Transmissions GmbH in Saarbrücken, Germany.
The transmission is controlled by an Electronic Automatic Transmission (EAT) ECU which contains software to
provide operation as a semi-automatic 'Steptronic' transmission. The EAT ECU allows the transmission to be
operated as a conventional automatic unit by selecting P, R, N, D on the selector lever. Movement of the selector lever
across the gate to the 'M/S' position puts the transmission into electronic 'Sport' mode. Further movement of the lever
in a lateral position to the + or – position puts the transmission into electronic manual 'Steptronic' mode.
The 5HP24 transmission has the following features:
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Designed to be maintenance free
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Transmission fluid is 'fill for life'
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The torque converter features a controlled slip feature with electronically regulated control of lock-up, creating a
smooth transition to the fully locked condition
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Shift programs controlled by the EAT ECU
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Connected to the ECM via the CAN for communications
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Default mode if major faults occur
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Diagnostics available from the EAT ECU via the ISO 9141 K Line.
The gearbox comprises three main casings; the bell housing, the intermediate plate and the main case. These items
are bolted together to form the housing for the transmission components.
A fluid pan is bolted to the lower face of the main case and is secured with bolts. The fluid pan is sealed to the main
case with a gasket. Removal of the fluid pan allows access to the valve block and solenoids and speed sensors. The
fluid pan has four magnets located in each corner which collect any metallic particles present in the transmission fluid.
A non-serviceable fluid filter is located inside the fluid pan. If the transmission fluid becomes contaminated or after
any service work the filter must be replaced.
The bell housing provides protection for the torque converter assembly and also provides the attachment for the
gearbox to the engine block. The torque converter is a non-serviceable assembly which also contains the lock-up
clutch mechanism. The torque converter drives a crescent type pump via drive tangs. The fluid pump is located in the
intermediate plate, between the bell housing and the main case.
The main case contains the following components:
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Input shaft
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Output shaft
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Valve block and solenoids
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Three rotating multiplate drive clutches
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Three fixed multiplate brake clutches
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One freewheel, one way, sprag type clutch
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A planetary gear train comprising three planetary gear sets.
