The control of the oil stress while in the lock-up clutch is completed by two valves: the relay valve and the signal valve. In this sort of arrangement the sign valve controls the force on one particular side in the relay valve, which controls the pressure during the lock-up clutch. https://finndkmmm.topbloghub.com/40590381/how-much-you-need-to-expect-you-ll-pay-for-a-good-torque-converter-clutch