Torque converters are found in nearly every automatic transmission, many semi-automatic transmissions, most constantly variable transmissions, and are not found in manual transmissions.
The stall speed rating of a torque converter states the RPM an engine has to reach in order to start driving the wheels from a standstill. Most stock passenger vehicles have a stall speed somewhere around 1,500 RPM, but racing vehicles (especially those in drag racing) usually have a higher stall speed so the vehicle takes off at the RPM where the engine makes the most power.
Lock-Up Torque Converters
A typical torque converter has some losses in its operation, usually about a 10 percent difference between input speed and output speed. A lock-up torque converter has an extra component within it that will allow it to lock up to create a lossless transfer of power.