The Charge of the oil pressure while in the lock-up clutch is completed via two valves: the relay valve and also the sign valve. In this kind of arrangement the sign valve controls the stress on 1 facet of the relay valve, which controls the pressure within the lock-up clutch. https://torque-converter-clutch06283.bloggip.com/34319169/how-much-you-need-to-expect-you-ll-pay-for-a-good-torque-converter-clutch