Viscous couplings are used in vehicles to selectively control the torque on shafts, during start-off or in ventilation propellers. In a viscous coupling, power is transmitted continuously by means of liquid friction as the torque increases. Smooth power transmission is assured by WACKER AK-VISC silicone fluids. They offer long service lives at high temperatures and shear rates, low moment fade after long running periods, as well as low dependence of both the torque and the viscosity on temperature.