A. Planetary gear sets which are the mechanical systems that only provide the various forward gear ratios

B. The hysraulic system which uses a special transmission fluid sent under pressure by an oil pump through the valve body to control the clutches and bands in order to control the planetay gear sets

C. The torque converter which acts like a clutch to allow the vehicle to come to a stop. in gear while the engine is still running

D. The governor and the modulator or throttle cable that monitors speed and throttle position in order to determine when to shift