The primary question I have is...does .01 thickness increase from the HD to HDD frame make that much of a difference?

 

It does. A little can go a long way in structural design.

 

10%

 

That’s what is interesting. 10% thicker frame but with the heavy duty payload it increases payload by what, 600-800lbs? That’s like a 30-40% payload increase.

Is it not applicable to think of these increases proportionately?

I guess my real question is…is the payload on regular tow package SCREWs under rated for what the setup could actually be certified for?

 

That's just one component in the package.
springs, shocks, rear end, axle housing.
10% thicker frame ties it all together.
That .010 is on 4 sides of the frame rails box.
Makes a big difference.

 

It's not, really, because the payload rating doesn't factor in the thickness or stiffness of the frame. It's just not part of the calculation.

 

No, it is part of the overall consideration. You can not add to capabilities with weak foundations. Why do you suppose Ford makes different frames?

 

You'd have to ask a Ford engineer. All I know is, it doesn't factor into GAWR or GVWR, so it doesn't factor into payload. I'll give you that Ford wouldn't budget for an entirely different frame without good reason.

 

And you know THAT how?

 

Well... I was going to respond, but I remembered I already posted this info in this thread.