A four-wheel-drive system provides extra reserves of traction and gives a reassuring sense of safety, even in adverse weather conditions or on treacherous road surfaces. The system ensures superior handling stability, excellent straight-line running, plus optimum stability in crosswinds.

At the heart of the four-wheel-drive system is an interaxle differential, whose design varies depending on the particular system. The differential’s task is to distribute the drive forces variably between the front and rear axle. If there is a difference in the rotational speeds at the two axles, caused by the wheels on one axle spinning on a slippery or loose surface, for instance, the system will split drive torque accordingly between the axles.

At the same time, however, the smaller differences in rotational speed which occur when cornering or manoeuvring must be balanced out to prevent torsional stresses in the drive train. Nor must the differential interfere with the functionality of the ESP, ASR and EDL dynamic handling control systems. In order to cater to the widely varying demands, Volkswagen offers its four-wheel-drive system in three differential variants:

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