There was a time long ago when half of the vehicles on Earth wore Ford badges. There was another time, not long ago, when it only seemed that way. Still, there's little better evidence of greatness than when the primary complaint about a particular vehicle is that there just too many of them running around. And there are still plenty of 2003 models running around towing trailers -- but not all of them can tow the same amount.
A vehicle's ultimate towing capacity is its Gross Combined Weight Rating minus its curb weight; that gives you a base on what the chassis can handle. In this case, the chassis has a GCWR of between 10,000 pounds and 11,500 pounds depending on equipment, and a theoretical towing capacity of between 8,400 and 8,800 pounds. However, what the chassis can handle and what the small 4.6-liter and its drivetrain can handle are two different things. What the drivetrain can actually handle depends largely on the gearing -- which gives the engine more mechanical advantage -- and the transmission.
Loaded Trailer Weights
For manual-transmission trucks with a standard hitch: those with 3.08-to1 rear gears can pull 2,000 pounds. Regular-cabs with 3.31 gears can haul 2,900 pounds, and those with 3.55-to-1 gearing can move 3,500 pounds. Subtract 300 if you've got a SuperCab, and 400 pounds for four-wheel-drive trucks. All trucks regardless of transmission are limited by the hitch's class rating. Automatic-transmission trucks with fifth-wheel hitches can get the closest to the chassis' capacity. Fifth-wheel, regular-cab trucks can pull 7,200 pounds; again, subtract for four-wheel-drive and SuperCab configurations. Four-wheel-drive models with 17-inch rims and big 265/70SR17 tires are rated 500 pounds lower.