Tow rating is only 3500 for 6 cylinder trucks. The 3500 pounds stamped into the rear bumper is what the bumper itself is rated for. My 89 2wd 2.6 automatic is rated at 1000lb without trailer brakes, 2000 pounds with, per the owner's manual. That being said, those are very conservative ratings and I've towed about 2500-3000 pounds with my truck with no trailer brakes, and did not feel unsafe. The rear bumper will start to flex down a bit in the middle, but it's all I've ever used. Do not use overdrive. If you have an auto, lock it in 2 until you're up to speed then shift to drive. You wan't light throttle and high revs. Keeps the pressure up on the clutch discs. Coming up to a grade, force shift it into 2 before it downshifts, same thing, it will reduce wear on the clutches. If you have a manual, just keep the revs up and avoid 5th gear.
Towing a ton of coal, some bags thrown in the bed to get the tongue weight down. Towing a camry shell. Towing (2)14' sections of 15" c channel and a 3' piece(that one was dicey. couldn't get the tongue weight up. Had to keep it slow to not get any sway), towing a 1500lb granite surface plate. Trailer is around 5-600 pounds empty. A reinforced 5x8 from tractor supply with a 2x wood deck.
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