What transmits power from the engine to the transmission in an automatic transmission?

In an automatic transmission, the torque converter is the component responsible for transmitting power from the engine to the transmission. The torque converter functions as a fluid coupling, allowing the engine to continue running even when the vehicle is at a standstill and increasing the engine's output to the transmission during acceleration.

When power is transmitted from the engine, it flows through the torque converter, where it is converted from mechanical energy to hydraulic energy using fluid. This process helps to provide a smooth transition of power and facilitates variable speed changes without the need for a manual clutch. The torque converter also performs the function of multiplying torque, giving the vehicle the necessary power to start moving and to accelerate without stalling the engine.

In contrast, the clutch assembly is specific to manual transmissions, where it connects and disconnects the engine from the transmission. The gearbox refers to the arrangement of gears within the transmission that facilitates gear changes but does not directly transmit power from the engine. The axle is part of the drive line that transfers power to the wheels but does not engage directly with the engine or transmission for power transfer.