I towed a 3000lbs car on a full Uhaul car trailer a few hundred miles and I have the 2006 4.7V8 6speed 4X4 Quad cab and it was ruff up big hills and Sucked down the gas... the real reason I am Chiming in; is the squat... it dropped my rear a good amount (3-4inches).. enough that at night on-coming traffic thought I was highbeaming them... but most of the weight of the car was at the front of the Trailer so I could strap the car wheels ...

 

The 4000 lbs trailer brought the rear down but I never scrapped on anything. Stopping was not an issue, and the trailer had no brakes. But I have trailer brakes and all.