L322 Range Rover System Description and Operation
AUTOMATIC TRANSMISSION – ZF 5HP24
DESCRIPTION AND OPERATION 44-2-19
There are three drive clutches and three brake clutches used in the 5HP24 transmission. Each clutch comprises one
or more friction plates dependent on the output controlled. A typical clutch consists of a number of steel outer plates
and inner plates with friction material bonded to each face.
The clutch plates are held apart mechanically by a diaphragm spring and hydraulically by dynamic pressure. The
pressure is derived from a lubrication channel which supplies fluid to the bearings etc. The fluid is passed via a drilling
in the output shaft into the chamber between the baffle plate and the piston. To prevent inadvertent clutch application
due to pressure build up due to centrifugal force, the fluid in the dynamic pressure equalisation chamber overcomes
any pressure in the piston chamber and holds the piston off the clutch plate assembly.
When clutch application is required, main pressure from the fluid pump is applied to the piston chamber from the
supply port. This main pressure overcomes the low pressure fluid present in the dynamic pressure equalisation
chamber. The piston moves, against the pressure applied by the diaphragm spring, and compresses the clutch plate
assembly. When the main pressure falls, the diaphragm spring pushes the piston away from clutch plate assembly,
disengaging the clutch.