Abstract: An rpm-changing engaging device of a motor vehicle is controlled during an engaging process in such fashion that a curve is selected according to which the rpm difference based on the input rpm of the engaging device is adjusted between the input rpm of the engaging device and its output rpm by the engaging device indirectly or directly, corresponding to the value, determined prior to the engaging process or before the stopping of the motor vehicle, of a driving activity. A precondition is that the rpm difference, based on the input rpm of the engaging device and its output rpm. The curve is selected from a family of several engaging devices.

Abstract: A multiple-disk visco-clutch is arranged in the drive line of the front axle and the rear axle of a four wheel-drive motor vehicle. In order to prevent an overheating of the multiple-disk visco-clutch, such as when the vehicle is being towed, the visco-clutch is separable from the drive line by means of a shiftable toothed clutch. The lubricating-oil pressure, the intake pipe vacuum or other characteristic quantities of the motor vehicle may be used for actuating the toothed clutch when the internal-combustion engine is stopped, thereby automatically causing the separating of the multiple disk visco-clutch from the drive line.