Drive Axle - Locking/Limited Slip

Locking Differential Description and Operation
The All Wheel Drive (AWD) system provides On-Demand all wheel drive, distributing variable torque/power to the rear wheels via individual axle shaft assemblies. On-Demand drive is provided to each of the rear wheels only when slippage is detected at the front wheels. As long as there is no slippage at the front wheels, there is no front-to-rear speed differential and no need for rear wheel drive torque. In the event there is front-to-rear wheel speed differential slippage, a rotational speed difference between the Gerotor pump components (rotor and housing) occurs. In those instances, the rotor draws fluid from the sump and through the internal passages of the differential carrier, sending pressurized fluid to a piston (actuating the specific rear wheel clutch pack). In the event of a spare wheel (of smaller diameter) is used on any of the four positions, the wheel rotational speed difference is detected by the wheel speed sensors of the ABS system. The powertrain module directs the differential inlet valve to close and block oil flow to the Gerotor pumps. The inlet valve also monitors the sump oil for an "overtemperature" condition. If differential oil temperature exceeds 110°C (230°F), the valve will close and block oil flow to the Gerotor pumps. In both spare wheel usage and overtemperature conditions an activated inlet valve will illuminate the control panel AWD Disable indicator.

View the list of major components that make up the AWD system below.

AWD Disable indicator
The AWD Disable indicator is located in the instrument panel cluster. This lamp is used to inform the driver that the AWD system has been disabled and no torque will be applied to the rear wheels during a slip condition. The AWD Disable indicator is controlled by the powertrain control module via a class 2 message.

Differential Clutch Pump Actuator Check Valve
The differential clutch pump actuator check valve controls the oil flow to the Gerotor pumps. Without fluid pressure the pistons cannot apply the clutch-packs for rear wheel engagement. The actuator check valve will open upon engine start-up and remain open unless commanded closed by the powertrain control module. The actuator check valve also monitors the sump oil for an overtemperature condition. If differential oil temperature exceeds 110°C (230°F), the valve will close and block oil flow to the Gerotor pumps.

Powertrain Control Module
The powertrain control module monitors the data from the ABS controller and Rear Drive Module (RDM) for proper operating conditions. If inappropriate conditions are present the PCM commands the differential clutch pump actuator check valve closed, disabling the AWD system. The PCM also commands the AWD Disable indicator on.