I have the in rad cooler and the trucool 4739 mounted in my bumper today it was 96 degrees outside my fluid went up to 145 degrees but when i stopped in traffic and sat there i got it up to 165 degrees and stayed there if i didn't have the rad cooler it would be about 200 degrees or more cause no air flow over the cooler so yes mark is right the rad cooler is cooling my transmission air not heating it up if you grab the lower hose of the radiator it is actually warm to the touch not as hot as the upper hose the radiator on the 7.3 is very efficient.