LR3/Disco 3
The multi-plate clutch assembly for both centre (transfer box) and electronic rear differentials act in a similar way. The aim
of the multi-plate clutch assembly is to prevent excessive differential slip and therefore maximise the traction performance
of the vehicle. This is fundamentally different from the 'braked' traction control, which can only counter act differential slip
when it occurs.
A certain amount of differential slip is required to allow the vehicle to turn corners and to remain stable under control of
the Anti-lock Braking System (ABS). The transfer box control module monitors the driver's demands through primary
vehicle controls and automatically sets the slip torque at the rear differential via the electronic rear differential control
module. The system is completely automatic and does not require any special driver input.
The multi-plate clutch assembly actively controls the torque flow through the rear differential and optimises the torque
distribution in the driveline. The clutch assembly biases the torque from the differential to the wheels with the higher grip
and prevents the wheels with the lower grip from spinning.
By turning the input actuator disc, via the motor shaft, the output actuator is rotated. This movement acts on 5 balls in a
ramp mechanism between the input and output actuators and gives a defined axial movement. The movement forces the
pressure disc to induce friction between the sun gear and differential case via the clutch plates supported by the sun gear
and the plates supported by the clutch basket on the differential case. This frictional force inhibits the differential rotation;
the differential case and left hand differential side gear are locked together.
Electronic Rear Differential Control Module
The electronic rear differential control module controls the multi-plate clutch actuation. The control module is mounted on
a bracket located on the LH C-pillar, behind the trim.
Item Part Number
Description
1
-
Pressure disc
2
-
Clutch plate assembly
3
-
Pressure disc
4
-
Thrust race
5
-
Output actuator
6
-
Actuator balls
7
-
Input actuator
8
-
Bearing pre-load spacer
9
-
Reduction gearset
10
-
Actuator motor
