A drive unit for a motor vehicle including an internal combustion engine, a transmission and a hydrodynamic retarder. The retarder includes both a rotor and a stator wherein the rotor is mounted on the engine crankshaft or crankshaft journal and the stator is disposed between the crankcase and rotor.

The present invention involves a drive unit, specifically a drive unit for a motor vehicle having an internal combustion engine, a cooling system with fan and a hydrodynamic retarder with a stator, rotor and housing. The retarder is located within a space bounded on one side by the front of the crankcase, on a second side by the fan shaft which runs parallel to the engine shaft, and on a third side by the rear edge of the fan wheel. Viewed from the front, the retarder is substantially located within the fly circle of the fan wheel whereby the air flow generated by the fan wheel removes heat, generated by braking actions, from the housing of the retarder.

A motor assembly comprises a first end frame, a second end frame including at least one air outlet aperture, an air shroud surrounding a stator between the first end frame and the second end frame, the air shroud cooperating with the stator to form at least one air passage, and cooperating with the first end frame to form at least one air inlet aperture. The motor assembly also comprises a fan mounted on the rotating shaft, the fan operable to generate an air flow of ambient air through the at least one air inlet aperture, the at least one air passage and the at least one air outlet aperture.