Modern day torque converters use electro hydraulic Management with the lock-up clutch. The hydraulic circuit which locks/unlocks the torque converter clutch is managed using hydraulic valves. The valves are actuated directly or indirectly by solenoids. Torque converters are used in automatic transmissions because they enable the car to come back https://beckettvwtro.jts-blog.com/32968184/facts-about-torque-converter-clutch-revealed