The control of the oil strain from the lock-up clutch is finished via two valves: the relay valve plus the sign valve. In this type of arrangement the sign valve controls the stress on a single aspect of the relay valve, which controls the pressure while in the lock-up clutch. https://torqueconverterclutch10741.bloguerosa.com/33221823/the-2-minute-rule-for-torque-converter-clutch