The control of the oil force during the lock-up clutch is done via two valves: the relay valve and also the signal valve. In such a arrangement the sign valve controls the pressure on a single facet in the relay valve, which controls the tension inside the lock-up clutch. By https://torqueconverterclutch42851.tinyblogging.com/considerations-to-know-about-torque-converter-clutch-77926509