Four Wheel Drive (4WD) Systems

WARNING: This page is about a different car, the 2007 Lincoln MKX and 2007 Ford Edge. However, it is still accessible from the selected car via links, so may be relevant.

Torque from the engine is transferred through the transaxle to the power transfer unit (PTU). This torque is transferred from the driveshaft to the rear axle, which drives the rear halfshafts. The four wheel drive (4WD) system, referred to as intelligent all wheel drive (AWD) system, is always active and requires no driver input. The AWD system combines transparent all-surface operation and is capable of handling all road conditions, including street and highway driving as well as winter driving.

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.

The only serviceable components of the PTU are 3 seals. If any of the internal geared components, bearings or shafts are worn or damaged, a new PTU must be installed. The PTU is sealed from the transaxle and has its own oil sump.