Locking Differential Description and Operation: Notes

WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.

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 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, in use on any of the 4 positions, the wheel rotational speed difference is detected by the wheel speed sensors of the antilock brake system (ABS).

The powertrain control module (PCM) or the transmission control module (TCM) 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.