had a 1500 Chevy 5.3 that we pulled a two horse trailer with. It was fine here in Rhode Island with our rolling hills, but in Pa. every hill it shifted out of overdrive and the engine screamed all the way to the top. Gas milage was bad, and the shifting and engine noise sucked. If you get a 2500 or 1500 with the 6 liter engine you will not have these problems and will actually get better milage. My son has a new 6 liter 1500 Silverado, tows a two horse with dressing room and gets over 20mpg when not towing. I, myself have a 3500 Denali diesel now for the toyhauler.