I pull a big honking trailer in the mountains here and the tranny hasn't broken a sweat. Temps have stayed nice and cool with no burnt fluid so far (a weekend of pulling in 95+ heat with a 5k# trailer). Maybe if you were constantly towing it would be worth it, but most of the time the tranny is pulling just the X. Coolers also give you more points that can leak. Change the fluid more often as a precautionary measure, but it should be fine...Brake controller on the other hand was a good investment. The Xterra stops better with the trailer than without