Jack, there is a sprag clutch inside the torque converter of every automatic transmission that has a torque converter. The converter multiplies the engine's torque by a factor of around 1.4 to 1.6, by bouncing oil off a stator, which provides the reaction torque to add to the engine's torque. As the car speed increases though you reach a point where a stator is ineffective - you can't bounce oil off a stationary object unless the oil is moving toward the stationary object, so the stator begins to rotate with the rest of the torque converter. However each time the car slows down, or at low speeds each time you stomp on the accelerator, the spinning stator has to stop suddenly and become a real stator again. To achieve this it is connected to a spline on the front of the auto transmission housing, by a sprag clutch. That allows the stator to spin, stop suddenly, deliver maximum torque, then smoothly start to spin again, completely imperceptibly as far as the vehicle occupants are concerned. Here is a more detailed explanation:
http://www.ultimateconverter.com/article.html
