Abstract: In a hydrodynamic-mechanical transmission for motor vehicles, consisting of a torque converter followed by a planetary gear with hydraulically actuable shift mechanism associated with the several transmission elements to select the various speeds, the planetary gear including a first sun gear connectable by way of a first clutch to the turbine rotor of the torque converter, a second sun gear connectable by way of a second clutch to the turbine rotor, a planetary mount connectable by way of a third clutch, bypassing the torque converter, directly to the engine drive shaft, on which mount first and second planet gears in engagement with each other and with the sun gears are mounted, and an internal gear constituting the drive output and in engagement with second planet gears meshing with the second sun gear, the possibility exists of reaching the third, direct speed either by purely hydrodynamic means including the torque converter by engaging the first and second clutches, by purely mechanical means bypassing

Abstract: In the particular embodiments described in the specification, an all-wheel drive system is disclosed wherein either the wheels of both the front axle and the rear axle of a vehicle are driven continuously and the front axle and rear axle can be rigidly coupled with each other, or wherein the wheels of only one axle are driven continuously while the drive for the wheels of the second axle can be obtained automatically by means of a viscosity clutch arranged in the driving train between the front axle and the rear axle so that the front and the rear axles are coupled with each other essentially rigidly according to the torque. In addition, one or more coupling devices are provided which are constructed so that a decrease in the rotational speed of the front wheels, caused in particular by the actuation of the service brake, cannot be transmitted through the driving train to the rear wheels.