Transmission, automobile part that transmits the power generated by the engine to a driving axle. The power travels from the transmission to the drive shaft, then to the final drive. These 3 parts make up the drive train of an automobile. The transmission has several gears, which regulate the speed of the automobile by controlling the amount of power delivered to the driving axle. There are 2 types of automobile transmissions: manual, where the driver is responsible for shifting the gears, and automatic, where a device automatically shifts the gears when necessary.