Present day torque converters use electro hydraulic Manage for your lock-up clutch. The hydraulic circuit which locks/unlocks the torque converter clutch is managed applying hydraulic valves. The valves are actuated immediately or indirectly by solenoids. This happens if the motor vehicle is not in motion or comes to a quit https://torque-converter-clutch55307.theideasblog.com/34467887/the-definitive-guide-to-torque-converter-clutch