Abstract: A liquid-friction coupling comprises a liquid-containing housing, a shaft, which coaxially protrudes into the housing, and the interdigitating sets of inner and outer blades, which are axially slidably mounted on the shaft and in the housing, respectively, and are non-rotatably connected thereto. Annular spreading springs are disposed between adjacent inner blades or adjacent outer blades. The distance between adjacent inner and outer blades can be changed by means of an annular piston, which is operable from the outside of the housing. To permit control of the liquid friction coupling within wide limits, the annular piston has a planar inner end face, which extends close to the blades and substantially throughout the cross-section of the interior of the housing. When the piston is in its outermost position the liquid contained in the housing is not in excess of 60% of the liquid capacity of the housing. The liquid has a viscosity of at least 30,000 centistokes.