I am sure this has been discussed here before but I am not finding the threads by searching. I have a 2014 F250 4x4 SuperCrew SB that I tow a 5th wheel with. Being an uninformed newbie to towing a camper...I bought a camper that is legally too much for the truck. Can't undo either one of those decisions so I just have to move on at this point. And trading an almost new paid for truck is not an option either. So...I am looking for the details on how I can upgrade the rear of my truck to be technically equal to the rear of a SRW F350 with the 11,500 GVWR. I know it won't legally change the GVWR of my truck but it will make me feel safer about towing the camper we have. I have already installed AirLift bags on the back and at 65 psi...they level the truck with the 5th wheel attached. Let me state that so far I have not experienced any issues towing but I am considering making things worse by swapping out my 26 gallon fuel tank for a 50 gallon.

 

I think the main difference from F250 to F350 rear suspension is the size of the spacer block. Makes the F350 sit a little higher. Springs and Diff are the same in SRW trucks AFAIK.

 

I think NYCruiser is correct. My 250 is only 8800 gvwr but if you look at GAWR's my front axle was about 5200# and rear was @ 6200#. If I get close to those numbers I'm over 11000# and probably moving really slow

 

Correct me if i'm wrong but I believe if you change your gearing that might push you into legal territory?

 

airm4n I think it varies by sanctioning body

In PA you can get the title changed but you need info to back up your claim which needs to be signed by an inspection mechanic

 

There is no difference in a SRW truck other than the F350 had a 3 1/2" block where the F250 has a 2" block. Ford uses progressive leaf springs so the further they sag under load the more they are supposably suppose to hold. Now since your airbags at 65psi are keeping the truck level there really isn't a need to "upgrade", I u swap in the F350 block all it will do is keep the rear slightly higher and u could most likely reduce the PSI to 50 to keep the truck level while loaded. NOW if your trailer has the rear axle overloaded (unlikely) or has you over your gcwr THEN going to a F350 will keep you under the limit of the truck. Other than that 250/350 are identical i every way (yes u can have different packages that alter front gawr, etc)

iPhone from IB AutoGroup

 

It was my understanding that the F350 SRW had a "helper" spring that only gets engaged when enough load is placed on the rear.

 

That's the overload spring, It's also on the camper Pkg of the F250. Standard on the F350.

 

A lot of the info here is dated.

1) Starting at some point between 12 and 14, even F250s came with a 4" spacer block.
2) Wheel size must be at least 18". 17" wheels come with a reduced RGAWR even on F350s. The load index of the tire needs to be 126 or higher, stock 17" tires usually came with a 121 load index.
3) You can't "change" the GCWR by changing gearing, because it's a made up number and not a legal rating anyways.
4) Anyone EVER seen an RV tagged by a weight cop? Def never seen it in Texas or Free America, no idea about Kalifornistan or New Yawk.
5) Do things to make it drive better and forget about the paper numbers.

So the first thing to do it get scaled and find out exactly what you're playing with. Full load of everything, water fuel the works, on the truck and trailer, and see where you are. Check front and rear axle weights, total on the truck, and total combined.

Check your tires, make sure they have a high enough load index to cover the weight that's on the rear axle. This is arguably the most important rating you'll consider, because tires blowing out are a for-real safety problem that really does happen. If you aren't running stock 18s or 20s, check the load rating of the wheel. Check the trailer tires while you're at it, just to make sure.

If the truck sags, add airbags, or airbags combined with an add-a-leaf. Aftermarket shocks make a big difference in the "feel" of how the truck is handling weight.

Drive. Make sure you have enough stopping power, especially if there are big hills where you are. Upgrade brakes accordingly.

Drive more. Add a rear sway if the trailer really pushes the truck over in the back.

 

Wouldn't you need to replace the class 4 receiver hitch with a class 5, according my my research that's what's required for me to tow 12k on my f350

Lift blocks are truly aweful, they promote wheel hop and axle wrap of rough terrain. Should be avoided at all cost.

 

With a 5th wheel I don't really think the drawbar matters much.

For bumper pull yes you are correct, the drawbar specs are probably more important that tire load specs, because there's always the chance of someone stick a 5k or 6k rated ball into to mix just because "the parts fit".

 

My truck came with plow package springs up front and 10K GVWR package and 17" steel wheels.

 

Plow package only upgrades the Front GAWR. In the past (and maybe for '15, I'm not sure) it's included rear aux springs in addition to the +2 front springs and a larger alternator, but the RGAWR is determined by 1st) 250 or 350, then if a 350 2nd) base 17" or 18" rims, which in the '15 order guide is driven by the 10k or 11.4k GVWR package. In 2014 there was an actual "derating" package that was required with 17" base rims on an F-350 SRW, through the commercial ordering service.

If you look at the RGAWR on an F350 SRW, it will be higher with 18"s than with base 17"s. The stock 17" tire's 121 load index of 3195# will cover at max 6390#. The ~6800# RGAWR of a SRW F350 requires 18" wheels and tires with a load index of 123 or higher.

 

OP here...my truck came with 20's and also has the class V hitch...although I have a 5th wheel so that does not matter. I have the air bags but would like to also add the helper springs just for some added insurance. I have seen a few aftermarket add-on springs but not sure if they are better or worse than what they come out of the factory with. Also, since the F350 SRW truck comes in 2 different GVWR flavors (10K and 11.5K)...trying to find out what the difference is between them.

 

The difference in 10k and 11.4k SRW F350s is the ink used to print the number on the VIN sticker. Some states have different regulations for trucks over 10k GVWR, so the "10k GVWR package" is offered by Ford to change the legal number on the sticker. Mechanical differences are based on package selection apart from the 10kvs11.4k option. Heavy front service suspension, snowplow prep, and camper packages all alter spring rates selected and GAWRs, but won't change the GVWR.