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Discussion Starter · #1 ·
I thought about getting a new F350 but decided against $900 payments. I am looking for more payload capacity for my 30' toy hauler. On the scales I am right at my max door sticker payload of 2330# with an empty toyhauler and before I added my 70gal aux tank. Some weight is on the front axle i'm sure but not going to figure out the arm of moment for the aux tank. on the trailer I'm sure the water tanks in front of the axles will add pin weight while loading all the bikes behind the axles will reduce it.

I have read many threads about SRW/DRW conversions but have not found much (one thread) that discusses anything about 250/350SRW swap. I know the 04below had different axles, Am I simply getting confused on the specs for the 05+ 250/350?

If the axles really are different what all do I need to find from a 350 and swap over and what years will work? If the rear axles are the same in 2006 what is needed to increase the payload to that of the 350 just springs? I only tow 10-20 times a year from Houston to DFW then Hallet, OK and NOLA 3 of those trips so a DRW is out of the question.

From the door sticker:
Arpil 06 build date
Short bed 6.0L 4x4
factory 20"
3L axle (e-slip 3.73)
5600# front 6100# rear 10,000 GVWR
Spring code DDFF which from the best I can tell is
DD — F81A-5310-AGD, 5,600 lb
FF — 5560, leaf
 

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The biggest issue is no matter what axle you put under the back end, your truck was certified as an F250 when it left the factory. Sticking an F350 rear axle under the back means you still have an F250 and can only legally carry that weight. I can't blame you for not wanting the payments of a new truck, but who says you have to have a new truck. BTW hauling a fiver, DRW is the only way to go IMO. Brought mine home today in 40-45 MPH cross winds and was rock solid.
 

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The 250 and 350 SRW trucks from similar years have the same 10.5 rear axle. The difference is in the blocks, springs and door sticker. The problem is even if you change all that out it is still a 250 according to the VIN. Realistically unless you plan on getting a DRW truck, just add some airbags to it. That will get red of the squat and help with handling the load.
 

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Discussion Starter · #6 ·
My problem isn't GVWR it's the rear GAWR so being over weight combined isn't my concern. If the rear axles are the same 10.5" for both 250 and SRW350 what gives the 350 the extra 900lbs rear axle rating? Springs and the 4" blocks?

My toyhauler is 6,080# empty and rated at 10k but I doubt I've ever gotten close. Maybe 8,500 if that. I'll try to find the old weigh tickets and post up exact numbers.
 

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If the rear axles are the same 10.5" for both 250 and SRW350 what gives the 350 the extra 900lbs rear axle rating?

The rear axles are not the same. Those who claim that all Sterling 10.5" rear axles have the same 9k weight capacity are uninformed.


Ford owns and runs the Sterling axle plant in Sterling, Michigan. The engineers at Ford and Sterling Axle work together to produce the axles with the specs that the Ford designers need. Although the housing and the 10.5" ring gear is the same, there are numerous other parts that determine the actual weight limits of the axle assembly. Axle shafts, bearings, and various gears, for example.


Over the years, the Sterling axle factory built the Sterling 10.5" axle assemblies with weight ratings from 6,000 to 9,000 pounds. Ford specified the 6,084 weight capacity for the '99-'04 F-250 and 6,840 weight capacity for the'99 '04 F-350 SRW. Those weight capacities matched the weight capacities of the tires available at the time for those pickups.


That's no big surprise. If you study cost effectiveness, the higher weight capacity costs more money to produce than the lesser weight capacity. So wasting money by specifying the same axle weight capacity for the F-250 as the F-350 SRW would get the engineer fired by any decent MBA manager. Same for springs and other parts of the suspension. Remember that Ford produced millions of trucks with 10.5" Sterling rear axles, so a few bucks difference in cost per axle adds up in a hurry. Engineers hate us MBAs that hold their feet to the fire on cost per unit, but that's what it takes to make a profit.

Beginning with 2005 model year, Ford increased the GVWR and GAWRs of the SuperDuty SRW pickups. To meet the higher weight specs, the Engineers at Sterling Axle had to redesign the SRW axles to meet the new specs. F-250 rear axle weight capacity was increased from 6,084 to 6,200 pounds and the F-350 SRW rear axle weight capacity was increased from 6,840 to 7,280.

Ford did build one Sterling 10.5" rear axle with weight rating of 9,000 pounds @ground. The 2005-'10 F-350 DRW rear axle was rated at 9,000 pounds for SuperDuty pickups with a 5.4L gas engine, so perhaps that's what confuses the folks that claim all Sterling rear axles were rated at 9,000 pounds. They probably read something on the Sterling website that said the 10.5" axles had weight capacity UP TO 9,000 pounds. (Rear axles behind the more powerful diesel and V-10 engines in duallies were Dana 80 axles rated for 11,000 pounds, not the Sterling 10.5" dually axle behind the 5.4L gas engines.)
 

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Discussion Starter · #8 ·
Thanks smoky. So from what I gather I could use either the 04 axle or the 05 axle and both would have a higher capacity than my 06 f250. Then I would need to match spring weight to the axle. And just make sure I'm not exceeding all limits, legal or otherwise, and I'll be fine.

Anyone know if the 04 axles swap right over to the 05+ I can't find any reason not to. Think 08+ would fit?

what else I would need besides the axles and matching springs? The 4" blocks maybe? I'll research some more but I think the only benefit was ride height.
 

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Discussion Starter · #9 ·
Edit: seems people are saying the 04 axles are narrower. Still trying to find out about 08
 
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