I think overdrives build up more heat due to towing or even car trans due to "lugging" the motor. Builds more heat in the converter. Got to keep the trans cool. I temp gauge is key, imo.
not even towing, just normal driving... our 97 ram will kick into 4th (good) at about 40-45 mph but also kick into lockup (bad) seconds later, then it lugs... I have the big B&M 11x11 plate on it, plan on adding another with my gauge