The engagement and disengagement on the lock-up clutch is determined by the way the fluid enters the torque converter. The automatic transmission fluid can enter both throughout the front from the lock-up clutch or in between the impeller and turbine, powering the clutch. Slippage consumes power throughout the coupling period. https://torque-converter-clutch21851.yomoblog.com/40857444/torque-converter-clutch-an-overview