Torque Converter Lock-up Clutch

At cruising speeds the converter would otherwise waste energy as heat through fluid slip. The control unit engages the clutch partly or fully depending on speed and load. Fault codes such as P0740 relate to the lock-up circuit or its performance.

Fluid pressure presses a friction plate against the converter housing so the engine and gearbox turbine rotate together.

A worn lock-up clutch can cause shudder at steady speeds, higher fuel use and higher fluid temperature. Fluid condition strongly affects how smoothly the clutch engages.