The Charge of the oil strain while in the lock-up clutch is done via two valves: the relay valve and the sign valve. In this kind of arrangement the sign valve controls the force on one side on the relay valve, which controls the force in the lock-up clutch. By https://torque-converter-clutch63940.blogsumer.com/33447310/considerations-to-know-about-torque-converter-clutch