Transfer Case: Notes

WARNING: This page is about a different car, the 2018 Jaguar XE and 2017 Jaguar XE. However, it is still accessible from the selected car via links, so may be relevant.

The transfer case is an on-demand All Wheel Drive (AWD) system with compact chain and sprocket arrangement which provides a compact and low weight design.

The transfer case is mounted on the rear of the transmission housing and includes a multiplate clutch with electro-hydraulic actuator. The electro-hydraulic actuator is controlled by the Transfer Case Control Module (TCCM) which controls the amount of torque being transmitted to the rear and front axles.

The TCCM monitors inputs from other control modules on the High Speed (HS) Controller Area Network (CAN) powertrain and chassis systems buses. Inputs include:

Wheel speed from the Anti-lock Brake System (ABS) control module.
Steering wheel angle from the Steering Angle Sensor Module (SASM).
Yaw rate from the Restraints Control Module (RCM).
Position of the acceleration pedal from the Accelerator Pedal Position (APP) sensor.

The SASM transmits the steering wheel angle to the Steering Wheel Module (SWM) via a hardwired connection. The SWM then transmits the steering wheel angle to the TCCM on the HS CAN chassis systems bus.

Using these inputs the TCCM calculates and delivers an output to the electro-hydraulic actuator. The actuator in turn, provides pressure to the multiplate clutch to distribute the required torque between the front and rear axles.

The system provides continuously variable response within 165 milliseconds, with high torque accuracy to provide exceptional dynamic performance.

The transfer case also improves fuel economy by providing only the requested amount of torque to the front axle. If necessary, full locking torque is available at any given time and vehicle speed, depending on road conditions and vehicle load distribution.

The transfer case incorporates a pump-less lubrication system with active sump management. The pump-less lubrication system comprises a lower sump and an upper sump. The drive chain that transfers torque to the front axle also transfers oil from the lower sump to upper sump. Oil in the upper sump lubricates the multiple clutch, bearing and upper seal.

In addition to the omission of an oil pump, the active sump management system also has the added benefit of also enhancing fuel economy by reducing drag losses in the transfer case.