Four Wheel Drive (4WD) Systems

WARNING: This page is about a different car, the 2010 Mercury Mariner and 2010 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

The All-Wheel Drive (AWD) system consists of the following:

Power Transfer Unit (PTU)
Rear driveshaft
4X4 control module (coupling device control module)
Rear axle with coupling device

Torque from the engine is transferred through the transaxle to the PTU . This torque is transferred from the driveshaft to the rear axle, which drives the rear halfshafts. The AWD system, also referred to as an Active Torque Coupling (ATC) system, is always active and requires no driver input.

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 wheel slip between the front and rear wheels is detected, or if the vehicle is under heavy acceleration, the AWD system increases torque to the rear wheels to prevent or control wheel slip.

Serviceable components of the PTU are limited to the output shaft seal and flange, intermediate shaft seal and deflector, and the PTU transaxle compression seal. No internal components are serviced. There should be no need to remove the PTU cover. If any of the internal geared components, bearings, case cover or shafts are worn or damaged, a new PTU must be installed.