Rear Drive Axle Description and Operation (With G99)

Fig 1: Identifying Rear Drive Axle System Block Diagram

Courtesy of GENERAL MOTORS COMPANY

The rear differential clutch control modules function is to control the electronic limited slip differential. The rear differential control module receives a torque command signal from the chassis control module (CCM) according to the driving situation to achieve vehicle dynamics and traction.

The electronic limited slip differential system contains the following main components:

• The rear differential clutch control module
• The rear differential clutch solenoid valves
• The rear differential clutch motor
• The left and right rear differential multi-disc wet clutches

When the torque signal is received, the rear differential control module actuates the following components:

• The rear differential clutch motor
• The left and right rear differential clutch solenoid valves

The electro-hydraulic piston actuation engages the left or right limited slip clutch to allow active variable locking torque transfer to the left and right half shafts to enable torque vectoring and to allow cornering with differential.

The rear differential clutch control module monitors voltage levels, clutch temperatures, over-current, and circuit failures.

Whenever the hydraulic control system within the electronic limited slip differential system is opened, a service bleed procedure (Rear Differential Hydraulic System Service Bleed) with a scan tool needs to be performed to remove any air from the system.

If replacing the rear drive clutch control module, the module needs to be programmed/configured with rear differential clutch correction factors. The clutch correction factor is an alphanumeric value that is stored in the rear differential clutch control module and stamped on the rear differential clutch pack housings. The clutch correction factor is based on the valve current-to-torque performance of the individual clutch pack. The clutch correction factor helps to improve vehicle performance by adjusting software parameters to suit the mechanical hardware.

Configuring the rear differential clutch control module with the clutch correction factors might be required after certain service procedures are performed. Two eight digit values will be used during the programming of the rear differential clutch control module using the scan tool.