There are many limiting factors, but I imagine that one of the ultimate limiting factors for upgrading a truck's capacity is the frame of the truck, so I was wondering if there were any threads discussing frame differences between regular or super duty F150 / F250 / F350 trucks.

I like thinking about building a "stealth" heavy duty truck with an F150 emblem on it, but even if I put in a ZF tranny, upgraded rear axle, brakes, springs / shackles / hangers, etc., you eventually come back to the frame, and I've always wondered how much you could load on some of these trucks before actually bending something!

 

Thats what i'v done, i have a f150 with a 10.25 rear, f250 springs, air bags, and the 300 which is about to get a ZF.

The frame is strong, it will handle all the weight you want in the bed. The biggest thing iv noticed is towing really tong heavy trailers. Iv had well over 1000# on the hitch which is 4ft behind the axle( guy loaded 2k of pipe as far forward as he could) and could barely start to see it bow and flex just a tad. I think it'd pick the front tires up before it'd bend anything.

The only bent f150 frame iv seen(other then wrecks) was a tow truck that was winching a truck out of the mud, and had a crane on the back. So the winch point was creating leverage and picking the front tire up, so the chained the front of it to another truck. It bent right behind the cab.

 

The frame C channel is a full 3" taller on the F250HD and F350 trucks so bigger axles under an f150 frame does nothing to increase the safe load capacity.

 

I've often wondered how much of the curb weight differences between trucks is a function of the frame versus other components.

I suspect that these trucks are rated conservatively, and that the F250 / F350 trucks are built to operate at maximum load for near 100 percent of their duty cycle without incident.

By comparison, I suspect that the F150 frame could carry a lot if loaded and driven carefully on relatively smooth pavement, at least for short / occasional trips.

 

im not sure the the f250-f350 frames are any taller, i think they are just thicker. And early new body style f250s (98-99) had the same frame as a f150, with just rivited braces at the rear hump and at the front cross member

There is no easy way to increase your GVWR which is what limits your vehicle to carrying only so much weight.

But if you do carry a large amount all the time, i think its a good idea to have a bigger axle, brakes, and springs to help carry that load safely. That doesnt mean you can grossly overload it. And of course its easier to just buy a f250, but i kinda like my truck. And its awesome to have a ext cab short bed, which is rare for f250s. And its cool to have a Full Float with F150 badges. Haha