The original post asked for rail thickness and box dimensions comparisons, I don't think it's semantics.   But sure... it's your posting.  I'd like to know too.

Chadsalt, no I'm not trolling. I don't like newer Chevys, but have owned a great number of 1979 and older ones I loved. I got a bad taste for Dodge in 1982, when I bought a 1981 with a straight 6 that blew up with less than 40K miles on it.

Hosspuller, the frame with the thickest wall section may not be the strongest or the heaviest depending upon the configuration. What spurred me to ask is the stupid commercial they have with Toby Keith for Ford where he walks in with a section of frame from all 3 brands. Just looking to find out how valid Fords claim is here.

Hi, the Ford Super Duty replacing the Heavy Duty 97 and older was 1/8 inch thicker, again thicker in 2005 Super Duty being boxed under the engine and more frame cross member gussets. Ford 2005 is saying it's 10-17% thicker than 2004. The F450/550 is a thicker frame than F250/350 by at least another 1/8 inch as it was in 99, the difference between the pickup frame and the cab and chassis frame. It's been a one piece cold rolled C-channel frame since the 99 model. I just looked threw all my Ford spec press releases and don’t see an exact frame thickness. I know I have it somewhere on disc, it will just take a while to find it.

Dodge starting in 2003 on 2500/3500 are a 4 piece boxed frame with hydro-formed bed uprights and some gussets. GM I can't remember the year, but on HD2500/3500 it's a three piece frame with engine section being hydro-formed, middle piece stamped C-channel and the last piece under the bed cold rolled C-channel. There is a tinsel strength rating on these frames and that I'd have to look up.

There are two main theories at work with frames. The old one used by Ford on Super Duties and semi trucks using the flexible C-channel frames that twist under load and drive train torque.

The newer direction for frames is the boxed and boxed hydro-formed. The new Ford F150 starting in 2004 has a totally boxed frame that is hydro-formed. The Nissan Titan has a boxed frame. All Dodge trucks have a boxed frame. Using a stiffer boxed frame allows engineers to dial in the suspension for an improved ride.

The verdict is still out whether boxed frames will handle the weight loads on heavy duty pickup trucks. Dodge is doing well so far with 3 years of boxed frames. C-channels are easier to mount bed ball hitches and air bags. But the aftermarket manufactures are adapting to the boxed frame.

Hope the Boxframing on the new trucks don't hold/trap water and mud causing it to rot out like my old ( 1974 ) Landrover box frame did

Along the same lines as marketing trucks, Truck manufactures decide what their GVWR, payload, GCWR etc. is. Oh sure they test things, measure things, and then decide what numbers they will stand by. Bottom line is what warranty liability do they want to pay out. Kind of like a drug company deciding how many lawsuits will be still profitable before they pull a drug. It's all about cash flow.

What concerned me is as trucks have become more competitive, each year in the race for more power and payload, some manufactures raise payload and tow capacity without doing anything to the truck physically. That didn't make since to me and shows who decides these towing/payload #'s that the insurance companies and law enforcement folk consider the final word.

I've been giving Ford a hard time for years because their payload and towing capacity was below Dodge and GM. Not that they couldn't tow/haul as much, but that's the numbers Ford chose to stand behind. Then in the 2005 Super Duty, they finally raised their payload/towing ratings above GM and Dodge, but not just numbers, I was happy to see the numbers were justified in real changes to the truck like thicker frame, more gussets, thicker wheels, larger brakes, thicker axle tubes, heavier front suspension etc. So my hats off to Ford raising their ratings and backing it up with a stronger truck.