Abstract: A combination electric motor and transmission unit device has two inputs and a rotational mechanical output, at least one of the inputs being of electrical power, to a corresponding integral combination of an electric motor means with a transmission means. The directions of rotation and the rotational speeds of the two inputs can be controlled to provide the mechanical output at any desired rotational speed with peak power output, depending on the controls, thus providing an ideal infinite speed device. The device employs a novel arrangement of a differential unit or a planetary gear unit. The combined motor and transmission device is lightweight, requires a small number of moving parts, and is useful in vehicles powered by electricity, including for regenerative braking. Another embodiment of the drive device is useful for a flywheel for peak power supplementation and also regeneration.