Rear Axle Weight Rating

[schaibaa]

Hi Guys,

Just found a document from Ford the says the SuperCrew rear axle weight rating is 3700lbs. I guess I'm surprised that the standard F150 with the max payload package has a stronger rear axle. Does anyone know if this is a situation where the axle was de-rated for some reason?

https://www.fleet.ford.com/truckbbas/topics/2014/2014F150_techspecs.pdf

 

[t_j]

It's wider than the standard axel so it will be weaker

 

[schaibaa]

That seems unusual since the super duty axles are wider than a standard F150. I'd imagine the wheel bearings are roughly the same distance from the hub as a standard F150 - I can't think of any real reason the width would matter.

 

[t_j]

Because it's the same tube size and the weigh rating of a span is based on material dimensions and span length. I'm sure the super duty axel tube is larger in some way than the f150 tube

 

[Nv Guy]

It's not just the axle assembly, you need to factor in tire capacity & springs as well. it's rated lower than a max payload because it's a Raptor, not a max payload truck.
This is the same as saying a Clydesdale and a quarter horse both have hooves, so both should run just as fast.

And the Super Duty will have a full floating axle design, larger gears & possibly brakes which add capacity as well.

 

[schaibaa]

Well they are E rated tires and I'm just trying to understand the differences. Analogies aren't very useful here - "because it's a raptor" doesn't make much sense. The strain on the rear axle over desert whoops is pretty extreme. A 1G landing would significantly overload the rear axle rating - I know that's just an impulse force but of all the bent frames, I've never heard of a damaged axle.

Gears wouldn't change the axle load rating.

 

[Deleted member 12951]

What are you trying to accomplish? You are asking this for a reason, no?

 

[Nv Guy]

Well they are E rated tires and I'm just trying to understand the differences. Analogies aren't very useful here - "because it's a raptor" doesn't make much sense. The strain on the rear axle over desert whoops is pretty extreme. A 1G landing would significantly overload the rear axle rating - I know that's just an impulse force but of all the bent frames, I've never heard of a damaged axle.

Gears wouldn't change the axle load rating.

One of the factors of an axle load rating is the suspension- and if you haven't noticed, Raptors have a unique suspension, so yes - "Because it's a Raptor" does make a difference.
Axle ratings are not calculated in a vacuum, the entire package is considered.
Several guys here have broken axle shafts, so it does happen.

 

[schaibaa]

What are you trying to accomplish? You are asking this for a reason, no?

Yes thanks for bringing this back in to focus.

About 5-10 times per year, I have a ~5,000lb total weight (trailer and contents) I'm pulling right now and as mentioned above, the rear suspension on the Raptor doesn't do so well - even with that weight.

I pull around a track car on an aluminum open trailer - I'd like to upgrade to an aluminum enclosed ATC ~28', which will add about 3000lbs, plus I'll put some more crap in it so I'm thinking I'll be 9,000-9,500 max.

I'm going to add the RPG stage 2 kit with the 4" bumps that increases payload, but weight distributed, I'll be a bit over the axle ratings.

I only go ~150 miles each way, and only 5-10 times per year. I'm just trying to figure out if the axles are up to the task. I love the Raptor and would rather not buy a Super Duty when I only do it 5-10 times per year for relatively short distances.

I'm totally confident in the brakes, with the RPG stage 2 I'm confident in the rear end, and other F150's have a much higher tow/payload rating, so I'm confident in the chasis and towing dynamics. I'm just not quite sure about the axles - I would be pushing them a couple hundred pounds over their stated limits. If they are de-rated due to it being a "total package rating" as suggested above, then I'm probably fine.

I know it's not the greatest idea to do this, and I do like the new Super Duty, but I like the raptor more.

Aside from the RPG stage 2, I could also go with a Trailer Toad (mostly used for RV's) - but that would take all of the weight off of the truck.

Thanks!

 

[EricM]

You are not going to damage the axle towing 9000 lbs. However, you are exceeding the tow rating of the vehicle, which is illegal. You gotta remember, Ford sold the truck rated to carry/pull certain weights, which is what it's legally allowed to carry. You cannot increase those numbers, no matter what you do to the truck.

Cue the speeding and window tint comments....