The control of the oil stress during the lock-up clutch is completed through two valves: the relay valve as well as the sign valve. In this sort of arrangement the sign valve controls the strain on 1 side from the relay valve, which controls the force during the lock-up clutch. https://torque-converter-clutch53073.blogozz.com/33368396/torque-converter-clutch-no-further-a-mystery