A torque converter is used in vehicles with automatic transmissions to connect the transmission to the engine. The converter transfers movement from the engine to the wheels and allows the engine to continue working slowly when the vehicle is stopped.
Torque converters consist of a pump and two fans, the impeller and the turbine, that are inside a sealed chamber full of transmission fluid. The engine spins the pump so that it flings fluid toward the outside of the torque converter, causing the turbine to spin. The turbine connects to the wheels through the transmission moving the car. When the brakes are applied, the turbine stops spinning, and the impeller still moves slowly, allowing the engine to remain working.