On extreme pulls in the mountains, my trans temp will get to 210-215 but not for very long and the coolant temp has to rise to 240ish for that to happen. As soon as you crest the mountain, the temps start to drop. There is no need to add any extra transmission cooling capacity especially if you are only going to tow half the truck's rated load.

 

what does your trans temp run on the flat and unloaded . and i am over on the trucks gvw the truck weighs 8360 ,2215 king pin weight , total trailer 13,310 total 21,670 and 23,500 is cgvw don't think towing at 100 % would be that smart . the dealer told me it was 7400 curb weight teach me to listen to a sales man and not common sense

 

My gross combination with a 37' fifth wheel toy hauler is just over 24,000 lbs. Trans temp just cruising with the truck is 195 to maybe 202. You need to realize that the trans temp is controlled by a thermostat. It will keep itself at or about 200 most of the time. As the load increases, you will not see the trans temp increase very much until the engine starts taxing the cooling system hard then it will go up. I think the worst I ever saw was like 223 in the heat of Summer on a steady 6-7% pull for 4 or 5 miles. That is working the truck for all it has topping the crest at 62+ mph.

I had concerns initially about how hot the trans seems to run with no load, but it really is no different than saying that the coolant temp runs 205 all the time that you have no cooling capacity beyond that.

 

Thanks for the info ,just gunshy still old school