Overhaul - ZF 4HP22: Description
Transmission is a fully automatic 4-speed unit, with 4th gear being an overdrive unit. The transmission is equipped with a torque converter incorporating a lock-up clutch and planetary gear set.
Starting off from a standstill is performed by the torque converter which acts as a fluid coupling and a torque multiplier. Once transmission input speed approaches that of the engine, torque converter acts only as fluid coupling. In 4th gear, torque converter lock-up clutch engages automatically, depending on road speed, so that there is a direct mechanical link between engine and transmission. See Fig 1 .