Hybrid drivetrain for a vehicle

The drivetrain includes a differential mechanism having four or more input/output elements and having two degrees of freedom. The input In from an engine, the output Out to a drive shaft, and two motor-generators MGi and MGo are assigned to the elements, and one of the elements other than the element to which the output assigned is provided with brakes B. By braking the element other than the output with the brakes, a large reduction ratio can be achieved, so startability can be improved without enlarging the capacities of the motor-generators.