A drive unit for a motor vehicle having an engine; a transmission featuring a transmission housing; and a retarder featuring a rotor and a stator. A retarder shaft is provided that is supported by two bearings which are offset along the axial length of the retarder shaft. At least one of the bearings ("outside bearing") is supported by a wall ("outside wall") of the transmission housing. The retarder shaft protrudes freely beyond the outside wall of the transmission housing. Disposed on the retarder shaft, outside the outer bearing, on the outside wall, is a sealing component. The sealing component seals the clearance between the retarder (or pinion) shaft and the outside wall, preventing passage therethrough of the transmission oil and the operating medium of the retarder.