The rear drive module (RDM) in this vehicle consists of an aluminum housing which contains a gerotor fluid pump, clutch pack and a differential. It has a common fluid reservoir.
The on-demand rear differential distributes variable torque/power to the rear wheels via individual axle shafts.
The on-demand system operates as follows: only when front wheel slippage is encountered torque/power is proportioned to the rear wheels. As long as there is no front-to-rear speed difference; there is no torque/power to the rear wheels.
When front-to-rear wheel slippage does occur, the rear differential (gerotor) pumps fluid stored in the sump to a piston which actuates a clutch pack, which then distributes torque/power to the rear wheels.
The system has an integral protection device that reduces rear wheel torque when excessive heat is generated, thus protecting the RDM.
Rear Differential Assembly Fluid
The rear differential assembly uses a specifically developed synthetic hypoid fluid which is intended for a lifetime service interval. However, proper fluid level must be maintained to ensure proper rear differential assembly operation.
The fluid level range for proper rear differential assembly operation is 700-800 ml. New service replacement units will be shipped dry (without fluid). Fill new units with 750 ml of GM VERSATRAK fluid.
