Contemporary torque converters use electro hydraulic control for the lock-up clutch. The hydraulic circuit which locks/unlocks the torque converter clutch is managed using hydraulic valves. The valves are actuated instantly or indirectly by solenoids. The associated fee to exchange a nasty torque converter could vary appreciably based upon several components. https://torqueconverterclutch61582.glifeblog.com/32950307/torque-converter-clutch-an-overview