Independent rear suspension. The Long wheel base goes up to 660/6600. There is no axle tube that has to carry that weight so they can rate it higher.

 

My navigator has a higher GVWR than a HDPP...

 

Disclaimer - I'm not recommending that anyone exceed Ford ratings

However, I have reason to believe the factory Class IV is much stronger than it's ratings suggest. I know a guy who repeatedly towed trailers full of wood with tongue weights well in excess of 1000 pounds with a weight carrying hitch. I've since helped him set up a WDH. His most recent load looked really heavy so I weighed the tongue - 1,700 pounds on my crane scale.

 

The weight carrying rating you see on OEM receivers is going to be based on the vehicle rating under SAE j2807. It is not the rating of the receiver itself tested independently of the truck. Under SAE j2807 guidelines the F150 has a weak weight carrying rating, it’s not the end of the world.

 

Me thinks you should consider actually reading SAE J2807 before making such a conclusion.

 

I’ve read it completely and understand it. How about you?

 

Me? I'm just the guy who is confused how anyone could read and understand it, yet write what you did. Maybe you could clarify by posting just an excerpt to substantiate your claim? Looking for the part where the receiver rating is based on the truck rating for weight carrying. We can discuss how the receiver can have a 10,000 WD rating on a truck with a 5,000lb tow limit later.

 

Ford has been putting stickers on the receiver that reflect the specific TWR of the truck for years it case you’ve missed it. If you just tested the receiver to SAE j684 standards still attached to the truck there’s no doubt the weight carrying rating would be higher. The vertical down force is still 1,000 lbs in most cases when a WDH is used.

 

I think 2015+ Expys all have the 660 weight carrying short or long. The ‘14 and previous 5.4L Expeditions are all 600 weight carrying. Both have the same max rating of 9,200 weight distributing so not sure where the extra 60 weight carrying came from for 2015.

 

As established above, the 500 pounds WC rating is not a limit of the receiver itself but the truck. And to be perfectly clear, it's not actually a physical limitation of the truck, but instead a legal limitation based on how the truck was tested and rated. A manufacturer doesn't have to test and rate a vehicle to the physical limit where it will still pass the SAE standard. For example, Ford is comfortable with the 500WC rating on a short bed regular cab 2wd with the lightest available component. Ford uses the same rating with a long wheel base HDPP. Physically, the limitation of these to vehicles are not the same. Ford chooses to rate them the same. 3/4 and 1-ton trucks of years past all had the 500WC rating as well. The physical limitations off all these trucks are not the same.

It is what it is. And only Ford knows why.