I am researching this issue because when towing my toy hauler that weighs 11300 travel trailer I see temps in the output line of over 200 all the time. Especially when in traffic or parking. I have an auto and even using tow/haul mode I have no control over torque converter lock up. The trans cooler seems very small. I don't think I should have to replace the trans cooler on a one ton truck. Could my Torque converter be bad? How would I know? I actually pegged the trans temp gauge on our way into Yellowstone. Quite frighting!!!! I do use Amsoil.