Four-Wheel Drive Systems - Overview

NOTE: The AWD system may be referred to as a 4WD system or Active Torque Coupling (ATC) system in other service information, owner literature, or messages located on the message center.

The All Wheel Drive Systems consists of the following:

PTU (Power Transfer Unit)

Driveline Control Module (DLCM)

The Power Transfer Unit (PTU) system consists of the following components:

Power Transfer Unit (PTU)

Power Transfer Unit (PTU) Actuator Motor
Oil temperature sensor (If equipped)
PTU Oil Cooler (Oil to Water Type) (If equipped)
Actuator fork. Includes PTU position sensor B.
Motor Actuator. Includes PTU position sensor A.
Gear reduction
Dog clutch
Front halfshafts
Driveshaft
PTU cooling fan (If equipped)

The RDU (rear drive unit) consists of the following components:

RDU actuator motor

Ball ramp drive plate

Ball ramp driven plate

Spur and idler gears

Drive shaft coupling (Plunge style joint companion flange)

Drive shaft speed sensor

RH (right-hand) half shaft

LH (left-hand) half shaft

Multi-plate clutch pack

Intermediate shaft (splined to clutch discs)

Differential side gear

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 rear wheels. During normal operation, most of the torque is delivered to the front wheels. If different wheel speeds (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 the duty cycle to the RDU Coupling motor. The RDU Coupling motor commences an RDU clutch activation, in the Rear Drive Unit (RDU) which in turn sets a ball ramp device in motion. The ball ramp device applies the main clutch pack in the RDU and increases torque to the rear wheels as necessary. When the AWD system is functioning properly, there should be no perceived speed difference between the front and rear axles when launching or driving the vehicle on any uniform surface. Traction should be similar to a part time 4WD system operating in 4H (4X4 HIGH), but have no binding in turns.

AWD Gear Ratios

Engine	Transmission	Rear Drive Unit (RDU) Gear Ratio	Power Transfer Unit (PTU)
2.0L(Petrol)	8F35	2.58	0.38:1
2.7L(Petrol)	8F57	2.58	0.38:1
2.0L(Diesel)	MMT6	2.58	0.38:1
2.0L(Diesel)	8F40	2.58	0.38:1
2.0L(Diesel)	8F57	2.58	0.38:1