The torque converter clutch comes into action to mitigate the inherent inefficiency from the fluid coupling at greater speeds. F (free-movement position): at this point there is no load around the turbine, the velocity ratio is very close to one, which means which the turbine speed matches the impeller pace; https://torqueconverterclutch52840.blogdomago.com/33137409/the-best-side-of-torque-converter-clutch