This means that there is a lot of electric power dropped within the torque converter, dissipated as heat. So that you can increase its efficiency, suppliers extra a lock-up clutch for the torque converter. Should the torque converter slips even though driving, this can cause unneeded heating in the transmission https://martinbmwfm.blogvivi.com/34595153/a-simple-key-for-torque-converter-clutch-unveiled