Ford has been making a huge deal about the F-150's fully boxed frame (even though all the other trucks have it too). I was wondering why the super duties do not have a fully boxed frame. It seems logical....

Here is an '08 F-450 super duty:

 

I really cant see very much in that pic... Are you sure that its not actually, fully boxed, just not a ladder frame?

 

If you look at the area of the pic "under" the driveshaft you can see the cables that run along the inside of the frame on the driver's side. It's just like the frame on my truck, which is not fully boxed.

 

those are fuel lines, and looks to me like its on the outside of a fully boxed frame rail... let me see what other pics i can find to help prove you wrong

 

Ooh, no need, my bad. I thought the fuel lines were recessed in the frame like mine (I remember because that's where my fuel filter is located). But now that I look closer I see the bottom of the frame and I think it is fully boxed....

But pics would be great.

 

Doh, you win https://www.f150online.com/forums/sh...highlight=rust

Oh well it definetly looks thicker, and much stronger then my frame does

 

Aww man I conceded way too early!

Doesn't that seem odd that it's not fully boxed? Isn't that supposed to help a lot?

 

hahah yea well i came on a little strong without knowing all the facts

But yah full boxed frame helps with twisting, and impacts, but adds weight. My best guess is that if the truck is over a certain weight (4dr dualie) then they either have to pay more to make them, or the consumer has to pay more to register it etc...

So simple answer is i bet it has to do with the truck would be too heavy with a fully boxed frame

 

Hmm... well that's good enough for me.

 

If you're happy im happy

 

I know that the front end frame rails are fully boxed on the new Super Duty. The ones under the bed are not. It's strange that they did not fully box the full length of the frame. I also know that the frame rails are much thicker on the Super Duty.

 

I dont know if this was discussed on this board or thediselstop but it seems that they dont fully box the frames because it would make the truck too ridged. Due to the higher weight raitings/capacities of the super duty trucks the frames need to bend/flex slightly under exterme loads.

 

You basically got it.

With 1/2 ton trucks the powertrain and suspension are the limiting factors for towing. they can only go so high, where as with the super Duty trucks, Big rigs etc, they have much heavier suspensions and larger powertrains. On the smaller trucks having a rigid frame adds stability when towing, and due to the powertrain limiting max weight possibilities it becomes an advantage. When you go to a Super Duty truck if you had a fully boxed frame dealing with the 15,000-24,500 pound loads it would have too much stress on individual points due to a lack of flex in the frame- causing them to snap or break.

 

That makes sense.

 

Good explaination Lumadar!...especially when pulling heavy trailers / equipment in an off-road situation. I've never seen any big rig - 4X2 or 4X4 with a fully boxed frame. Thats' why for comfort the cabs sit on their own suspension or air-bags because of the flex.