The Haldex coupling has the major advantage of being electronically controlled and having a very fast response. This allows it to work very effectively in conjunction with the anti-lock braking system (ABS), the traction control system (TCS), the electronic differential lock (EDL), and the electronic stability programme (ESP) - all these assistance systems are fitted as standard in the Passat.



4MOTION is always active

As soon as differences in the speeds of rotation between the front and rear axles occur two annular piston pumps are activated which build up pressure in the multi-plate coupling (Haldex system) thus "coupling" the two axles to each other. The transmitted torque can be varied by adjusting the pressure on the coupling plates, thus controlling the flow of power between the front and rear axles. The coupling provides an infinitely variable torque transfer between the front and rear axles. In extreme cases up to 100 percent of the available torque can be transmitted to the rear axle. In the normal case with the vehicle travelling in a straight line at a constant speed with no differences in the wheels' grip, 90 percent of the available torque is transmitted to the front axle and ten percent to the rear axle. The Haldex coupling is driven by the propshaft.



4MOTION is fast

The coupling responds to "commands" from the 4MOTION electronic control unit extremely quickly. As soon as the Haldex coupling registers front axle slip, the required torque is transmitted to the rear axle. The compact coupling can transmit a torque of 3 200 newton metres to the rear axle.

previous page


















Related Links: www.vw.com