Torque converter
The torque converter is an essential hydraulic component located between the engine and the automatic transmission. It replaces the clutch of manual vehicles by allowing progressive decoupling when stopped while transmitting power when in motion. The converter consists of three main elements: the pump (driven by the engine), the turbine (connected to the input shaft) and the stator (fixed, with an internal one-way clutch). Transmission fluid circulates between these elements and multiplies torque at launch (up to 2.5 times), while allowing lock-up at high RPM to reduce losses. ZF 6HP, Mercedes 722.6 and Aisin units use solenoid-controlled lock-up. Poor fluid quality, worn turbine seals or a faulty stator cause characteristic symptoms. Regular fluid changes extend its lifespan.
Malfunction symptoms
Slipping at launch or under acceleration, shudder or vibration when hot during lock-up, clunking noise, fluid overheating, burning smell. Worn turbine seals often cause typical hot shudder on ZF 6HP.