A torque converter can go lousy for a variety of reasons, and these issues may lead to weak performance, diminished gasoline effectiveness, and perhaps complete transmission failure. That is a function outside of what a simple fluid coupling presents, which could match rotational speed but isn't going to multiply torque. https://kameronipsvu.blazingblog.com/34263837/not-known-factual-statements-about-torque-converter-clutch