The torque converter clutch solenoid is always energised (trapped on) which interprets to the torque converter getting usually locked. This means that there's a number of energy lost inside the torque converter, dissipated as warmth. In an effort to improve its performance, brands included a lock-up clutch on the torque https://torqueconverterclutch20741.kylieblog.com/34529641/torque-converter-clutch-an-overview