I finally had a chance to give my truck a *little* bit of a challenge. Went for a 4hour drive towing all my sisters stuff back in a 6'x12' u-hall. The truck drove as if the trailer was not even back there. Only problem was the rear blow out (road hazzard) I got on the way to her place.

After loading up the back of the truck, the bed, and the trialer in 101 degree heat I got cleaned up and hit the road home. I used the tow-haul mode when the trailer was full, different shift points but still drove as if the trailer was not even back there. I did notice that when I got home and was in the stop / go traffic every time I stepped on it the engine made a noise that I had not heard before (or since). It sounded like a big rig truck with extra fans going hard or something until I hit about 20mph. I did like how it down shifted when slowing down, was pretty cool.

BTW, I got about 14.9mpg towing an empty u-hall south and about 14.6 mpg towing a full u-hall/truck back north.

 

Yes, the cooling fan would come on hard when heating up. When mine is working hard on hot days the fan gets loud as well. Just the tow machine doing all the stuff it is designed to do under given situations. Don't worry, sounds like your getting the same grin I'm getting when working the ol' Tow Beast.

 

I did the same this last weekend, loaded it up with a 3500 lb slide in camper and a 5k boat, another interesting thing I noticed is that it appeared that I got better mileage using the tow haul mode even though it reved much higher than without it, than I was getting when not using tow haul mode.