Do-It-Yourself High Performance Car Mods

The Mysterious Torque Converter

For a device with only three moving parts, a torque converter can be complicated to understand. The parts inside a basic torque converter are the impeller, the stator, and the turbine, which sit in a housing full of transmission fluid. The impeller is shaped somewhat like a hollow half-bagel filled with fins. It connects to the engine and gets the fluid moving. The turbine is a mirror image of the impeller and transmits the motion of the fluid to the output shaft. The stator is a finned disc that fits between the two. A oneway clutch connects the stator to the transmission housing.

At steady cruising speeds, the turbine spins at almost the same speed as the impeller. The stator freewheels at a speed somewhere in ...