Steyr-Daimler-Puch Fahrzeugtechnik (www.steyr.com) has developed the Geromatic traction system, which acts like a viscous coupling but is superior in several respects. The torque is transferred by means of friction plates, similar to an automatic transmission. The frictional connection is built up when an actuator, moved by a gear pump, presses the plates together. The hydraulic pressure of the pump depends on the speed difference. Pressure build-up and characteristics of the coupling can, to a great extent, be adapted to the application of the vehicle. Applications include front- or rear-axle lock, central differential lock, central coupling, and twin-system in the rear axle as a combination of central coupling and rear axle lock.