Inside VW.

A four-wheel drive system increases traction reserves and conveys a reassuring sense of safety even in bad weather or on rough roads. The system increases ride stability, as well as providing outstanding straight-line running and optimum side wind stability. 4MOTION thus not only offers decisive traction benefits, but also permits higher cornering speeds, thereby enhancing both safety and driving enjoyment – always dependent on the road conditions encountered.

Depending on the design, the core of a four-wheel drive system is usually a differential between the front and rear axles - the so-called centre differential. It distributes driving forces variably across the front and rear axles. If rotation speeds differ between the two axles, because one of them is slipping on icy or gravely ground, the system distributes torque accordingly across both axles, diverting a portion of it to the other axle as required. At the same time, minor differences in rotation speed during cornering or maneuvering also have to be compensated, to prevent torsional stresses in the drive train. Furthermore, the differential must not impair operation of the ESP (Electronic Stabilization Programme), ASR (Anti-Slip Regulation - traction control) and EDL (Electronic Differential Lock) driving dynamics control systems.

Volkswagen currently offers four-wheel drive systems in the Tiguan, Passat 4MOTION and Touareg 2. Given the widely varying demands to which the models are subjected, three differential types are employed:

• Haldex clutch
• Torsen differential
• Centre differential with electronically controlled multi-plate lock