heres from experience. A week ago i pulled my travel trailer to jacksonville, fl from houston, Texas. I have a 2005 ford f150 4.6l v8, auto trans. my trailer is 30ft long and weighs 5500 lbs. i had a k and n air intake, flowmaster exhaust and fireston ride-rite airbags on the back axle. whi;e the engine mods were nice and i never had a problem with overheating(engine, or tranny) the best money i spent was the airbags. they improve the ride exponentially. i would also reccomend something to monitor the transmission temp. i had no problems. write me if you want.