A motor vehicle power train includes a main drive engine with an output shaft for driving the drive wheels of the motor vehicle, an electric motor which includes a rotor and a stator, also for driving the drive wheels of the motor vehicle, an automatic transmission, with a plurality of selectively settable drive connections, a transmission input shaft and a transmission output shaft, the rotor of the electric motor being disposed in a drive connection between the output shaft of the main drive engine and the transmission input shaft, and can be disengaged from the output shaft with a clutch, and at least one ancillary unit which can be driven by the main drive engine. The rotor of the electric motor includes an exterior drive having a gearing of friction surface which has a driving connection to the at least one ancillary unit.