Four-Wheel Drive Systems - Overview

The AWD system consists of the following:

• Power Transfer Unit (PTU)
• Front and rear halfshafts
• Driveshaft
• AWD module
• Rear Drive Unit (RDU)
  • Hydraulic Pump Motor
  • Solenoids - LH, - RH
  • Clutch Packs - LH, - RH

The AWD system is an active system, which means it not only responds to wheel slip between the front and rear axles but also has the ability to anticipate wheel slip and transfer torque to the rear wheels before the slip occurs. The AWD system is active all the time and requires no input from the operator.

The AWD system continuously monitors vehicle conditions and automatically adjusts the torque distribution between the front and individually to the left and right rear wheels as needed. During normal operation, most of the torque is delivered to the front wheels. If wheel slip between the front and rear wheels is detected, the vehicle is under heavy acceleration or if the vehicle is in a handling event, the AWD system increases torque to the rear wheels as needed. When the AWD system is functioning properly, there should be no perceived speed difference between the front and rear axles when driving the vehicle on any uniform surface. Traction should be similar to a part time 4WD system operating in 4H (4X4 HIGH).

All-Wheel Drive with dynamic torque vectoring uses all four wheels to power the vehicle and independently controls the torque to each rear wheel applying torque as needed. The system also has the ability to over speed the outside rear wheel while cornering. This increases traction and handling performance giving the vehicle road holding capabilities that are superior to conventional two-wheel and four-wheel drive vehicles. The system is active all the time and requires no input from the driver. The vehicle also has different drive mode calibration settings that optimize all-wheel drive performance for various conditions.

The AWD system consists of front and rear halfshafts, power transfer unit (PTU), driveshaft, AWD module, and a rear drive unit (RDU) containing LH and RH clutch packs. The AWD system is controlled by the AWD module attached to the top of the RDU. Torque through the driveshaft is transferred to the rear wheels via commands from the AWD module, which controls the electric motor in the RDU powering the hydraulic pump to generate hydraulic pressure, the hydraulic pressure is controlled by solenoids for the left and right clutch packs and the hydraulic pressure is independently applied to the left and right clutch packs to transfer torque.

Serviceable components of the rear drive unit (RDU) are limited to the output shaft seals and fluid. No internal components are serviced. There should be no need to remove the rear drive unit (RDU) cover. If any of the internal geared components, bearings, case cover or shafts are worn or damaged, a new rear drive unit (RDU) must be installed. The AWD module and the harness between the AWD module and RDU are serviced separately. If a new rear drive unit (RDU) is installed it comes with the AWD module and is pre-programmed with the control logic and clutch matching configuration.