Description and Operation - All-Wheel Drive Systems - Overview

The all-wheel drive system consists of:

• PTU (Power Transfer Unit)

• RDU

• Transmission Control Module (DLCM)

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

• Power Transfer Unit (PTU)

• Power Transfer Unit (PTU) Drive Motor
• PTU Oil Cooler (oil-to-water type) (if equipped)
• Shift fork. Includes the PTU position sensor B.
• Motor drive. Includes the PTU position sensor A.
• Gear reduction unit
• Dog clutch
• Front half shafts
• 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

• Driveshaft coupling (splined companion flange)

• Driveshaft speed sensor

• Right half shaft

• Left half shaft

• Multi-plate clutch pack

• Intermediate shaft (splined to the clutch plates)

• Differential side gear

The all-wheel drive system is an active system, meaning that it not only reacts 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 slip occurs. The all-wheel drive system is active at all times and does not require operator input.

The all-wheel drive system continuously monitors vehicle conditions and automatically adjusts 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 (wheel slip) between the front and rear wheels are detected, the vehicle is under heavy acceleration, or the vehicle is in a cornering condition, the all-wheel drive system increases the duty cycle to the RDU clutch actuator motor. The RDU clutch actuator motor drives the RDU clutch actuation through ball ramp movement. The ball ramp device engages the main friction clutch pack in the RDU and increases torque to the rear wheels as needed. When the all-wheel drive system operates normally, there should be no speed difference between the front and rear axles when starting off or driving the vehicle on any uniform surface. Traction should be similar to a 4WD system operating part-time in 4H (4X4 HIGH), but without binding during turns.

All-Wheel Drive Gear Ratios