Anyone towing with a '08 GM 1500?

I have a 4WD 2008 Sierra extended cab with the 5.3 liter and a 3.73 axle and it is rated for 7500 lbs. 2WD will add another 200 lbs in towing capacity. I pull a trailer that scales at 7200 lbs ready to camp with 900 lbs on the hitch. There is just me and my wife in the truck and I am careful about what goes into the truck bed since I am using most of the 1500 lb load capacity and all of the towing capacity. I tow locked at third gear at 60-62 mph and in 100 Deg. F. ambient temperatures, the transmission runs at 200 Deg. F. Grades of more than 2 or 3 percent will force a shift to second gear and if it is a long grade, I will slow down to 50 mph to drop the rpm down some. I also change out the transmission and rear differential fluids every 35k miles.

I would reiterate that you definitely want to scale the trailer and while I have no immediate plans to move to a different vehicle, in your case I would recommend a 2500 for the load in question.