Your vehicle’s automatic transmission is responsible for transferring power from the engine to the drive wheels. The transmission continues to work by shifting up and down as you regulate the power and speed of the vehicle. Automatic transmissions contain the following major components: a planetary gear unit, a hydraulic pump, and a torque converter. The main difference between an automatic transmission and a manual is the torque converter, which operates similarly to a clutch. The torque converter automatically adjusts to engine speed and supplies power to the wheels of the vehicle. All of these components and internals heavily rely on transmission fluid to lubricate and create pressure so that the shifts remain optimal.