I've hauled a BobCat in mine numerous times, which weighs more than 2000 lbs. I've towed a travel trailer that weighs 10,000 lbs+ a few times through the mountains. Neither seemed to matter much to the truck, I was impressed.
I have a 1998 half ton supercab XLT 5.4 with the 4x4OffRoad pkg and heavy duty axle.