The transmission is the link between the engine and the wheels of your vehicle. Whether you drive a manual, automatic, or semi-automatic vehicle, the transmission plays a crucial role in the performance and reliability of your vehicle. The transmission keeps engine output matched with speed and load conditions. Because engines operate at high rotational speeds, the transmission reduces engine output speed and transmits torque through the differential, driveshaft, and wheels. As engine speed varies, the transmission switches between the gears that influence the amount of torque applied to the wheels. Transmission fluid performs a variety of duties, depending on the type of transmission. Transmission fluid acts as a cooling agent and protects the transmission by lubricating the internal gears and preventing corrosion and rust. In a manual transmission, clutches and gear shifts provide pressure and force—like engagement and disengagement—while in an automatic transmission, transmission fluid provides these same operational functions of force and pressure.