This suggests that there's a lot of energy lost while in the torque converter, dissipated as warmth. So as to increase its performance, suppliers added a lock-up clutch towards the torque converter. In case the torque converter slips although driving, this may lead to pointless heating in the transmission fluid, https://devinglmnn.iyublog.com/33124343/the-best-side-of-torque-converter-clutch