A transmission for an engine or motor with a reduced package size and increased efficiency comprising: an input sprocket, an output sprocket, a chain, and a planetary gear set. The output sprocket is drivingly connecting to the input sprocket through the chain. The output sprocket has a hollow center portion that receives the sun gear of the planetary gear set. The planetary gear set also includes at least two planet gears meshed with the sun gear which are mounted to a fixed planet carrier for driving a differential with a ring gear portion. When the input sprocket is rotated in a first direction, the chain drives the output sprocket and the sun gear in the first direction, and the sun gear drives the planet gears to rotate in a second direction, opposite the first direction, driving the ring gear portion and differential in the second direction.