What connects the engine to the transmission in an automatic transmission setup?

In an automatic transmission setup, the component that connects the engine to the transmission is the torque converter. The torque converter is a fluid coupling that allows for the transfer of power from the engine to the transmission while offering a certain degree of slip. This enables smooth acceleration and deceleration without stalling the engine, as it allows the engine to continue running at an idle even when the vehicle is stationary.

The torque converter accomplishes this by using a fluid to transmit power, which not only aids in engaging the transmission but also helps in multiplying the engine's torque when starting from a stop. This is particularly important in automatics, where a direct mechanical connection between the engine and transmission is not employed as it is in manual transmissions. The function of the torque converter is critical in providing the driving experience typical of automatic vehicles, making it the pivotal component in the connection between the engine and transmission.

Other components such as the gearbox and drive shaft play significant roles in the overall function of the vehicle's drivetrain, but they do not serve the specific purpose of connecting the engine to the transmission. A clutch assembly is relevant in manual transmissions but is not used in the context of automatic transmissions since the torque converter serves that purpose instead.