Thanks for the quick responses. Looks like heat could be a prob.
My question about the clutch lock was mostly for knowledge. I have a car that has shudders on light load as the tcc engages. It has a jatco 4 speed auto from about '87. The car has a "power" button which when engaged, changes the shift pattern, and disables 4th (overdrive) and the TCC as well. This is how it is supposed to work and it works. Driving with "power" engaged, the TCC problem is bypassed. I also have a gm car with a 4l60 type auto with no tcc problem, but wanted to know mechanically and ignoring any electronic management if there is any reason (lets say for academic purposes)that they could not be run permanently without the TCC lockup.
Both cars have trans coolers.