Featured on Audi A3 and Audi TT quattro® models, the only sports car in its class with permanent four-wheel drive, the latest generation of the Haldex clutch distributes power to the front and rear wheels to provide optimal traction.
If a difference in speed occurs between the front and rear axles, the system immediately builds up pressure by means of two pumps integrated into the clutch, and pressurizes the control piston. This then presses the plate sets together with a pre-defined force, so regulating the torque transmitted to the rear axle.
In normal driving conditions, the clutch directs 85 percent of the torque to the front wheels, but in extreme circumstances it is able to transmit as much as 100 percent of the forces to one of the two axles. The control unit does this in response to various sensor signals, including wheel speed, ABS braking functions and engine management.