Torque Converter? Where am I at? What is compromised?

My buddy had a 3000 stall many years ago. He thought it worked pretty good. But his car was always overheating the longer and farther he drove it. Turned out the converter had too much slip and was heating up the coolant thru the rad and tranny cooler. Tried the coolers every way. Didn’t help. Changed the converter to a factory high stall the heating problem went away. Kim