One with electric transmission and two with torque converter transmission. Four speed automatic without lockup torque converter. All variants are mated to a 5-speed torque converter gear box. This addition required the removal of the torque converter drain plug. Four speed automatic with lockup torque converter and electronic controls. It was available both with and without a lockup torque converter. This smaller transmission used a torque converter. The TAM's transmission is a Renk HSWL-204 automatic, with a hydrodynamic torque converter. Such devices include the steam turbine and the torque converter. The N360/N600 torque converter was about 5.5in. It is also found that efficiency of torque converter is maximum at very low speeds. The torque converter was operated by transmission fluid. An automatic gearbox (with torque converter) was optional for the petrol units. This torque converter was nominally about 7in. Both transmission and torque converter use a common powertrain oil.