9" rear end lengths for axle swap

Clutch, transmission, rear axle

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NUTNDUN
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9" rear end lengths for axle swap

Post by NUTNDUN »

I have a 9" rear in my 2wd 72 f100 but it has an open diff and 28 spline axles. I am mainly trying to get it on the road while not spending too much money. I want to run a 31 spline axle setup with a full spool. Instead of buying aftermarket axles right now which I really can't afford what are the chances of finding axles at the salvage yard that are the same length? I am going to put 4.11 gears in it and was originally going to just get a mini spool and run my 28 spline axles but instead of having to get the rear setup twice I would rather spend a little more on the full spool and the gears and find some stock 31 spline axles that are the same length.
George
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Re: 9" rear end lengths for axle swap

Post by mrtleavitt »

The 31 spline axles are 2 inches longer so basically you have two options:
1. Purchase aftermarket axles
2. Swap the whole rear end housing from a 31 spline vehichle which will consist of relocating the leaf spring purches
I'm sure this is not what you wanted to hear but you can't just simply swap axles between the 28 and 31 splines.
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Re: 9" rear end lengths for axle swap

Post by NUTNDUN »

I appreciate the info. I will just get the 28 spline open diff I have now welded up and put 4:11's in it. Once we get situated with moving and finances are there or until I snap an axle then I will put a 31 spline full spool and axles in it. It sucks trying to get so much done with a little budget LOL especially when it involves the whole truck.
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Re: 9" rear end lengths for axle swap

Post by fordman »

the easier way around is to get the whole rearend. and change the spring perch location to fit under yuor trucks and with your leaf springs.
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Re: 9" rear end lengths for axle swap

Post by NUTNDUN »

I thought about doing that but my only problem with that is the truck is lowered and the rear tires are 295's and the tires sit inside the wheel well and are almost against the inner wheel well. I am afraid of having to do some resizing and or having to get new wheels and tires if I go that route.
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Re: 9" rear end lengths for axle swap

Post by 1971fordcustom »

http://s205.photobucket.com/albums/bb31 ... d%20F-100/

1971 F-100 Explorer Special custom
1971 F-350 Flatbed
1966 Ford Galaxie!
1966 Ford F-250 4x4
1960 Ford F-750 FireTruck
1960 Gmc 6000 FireTruck
1962 IH R-185 Firetruck
1959 Ford Custom 300
1940 Ford Truck
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Re: 9" rear end lengths for axle swap

Post by NUTNDUN »

I appreciate the help. I found a 3.25 locker from a 77 but the axles will be too long and I don't know if they are 28 or 31 spline. I am going to try my luck with a few more junk yards in the area. Is there any way to tell if it is a 28 or 31 spline without pulling the axles? I know what to look for on the tag for the ratio and locker option. I am figuring on trying to find one the right width with a locker and 31 spline axles but in case I can't I could go with a 73-79 and just get the axles cut down and resplined.
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Re: 9" rear end lengths for axle swap

Post by fordman »

check this chart for some of our trucks options. http://www.fordification.com/rearends-ford01.htm
if you find a wider 31 spline rear end just swap the whole thing and relocate the perches so they will fit under your truck. no recutting axles and splines. that is a waste of money i think. i dont even know if it could be done .
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Re: 9" rear end lengths for axle swap

Post by Salt-shaker »

Hi..Ford did produce a 31 spline axle that was a bolt in for your application, with the correct wheel bolt pattern, ( they came out of a Ford truck ) I can get the lengths if that info will help. Just for thought though, prior to the 31 spline axles I never broke or twisted a 28 spline, and several years ago I installed a factory disc brake rear with 28 spline axles and have yet to break them even with some pumped big blocks. Perhaps I have been lucky..Take care..Steve
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Re: 9" rear end lengths for axle swap

Post by fordman »

Salt-shaker wrote:Hi..Ford did produce a 31 spline axle that was a bolt in for your application, with the correct wheel bolt pattern, ( they came out of a Ford truck ) I can get the lengths if that info will help. Just for thought though, prior to the 31 spline axles I never broke or twisted a 28 spline, and several years ago I installed a factory disc brake rear with 28 spline axles and have yet to break them even with some pumped big blocks. Perhaps I have been lucky..Take care..Steve
your right about that but they are harder to find. the chart shows where they were made prettty much in 72.
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Re: 9" rear end lengths for axle swap

Post by Salt-shaker »

WoW..Fordman what a great chart for identification..I cant seem to find the Dana 60 axles in there? can I be overlooking them? Thanks for the info...Steve
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Re: 9" rear end lengths for axle swap

Post by NUTNDUN »

Going by that chart if I can find a 71 with the original rear I might be in business. I will have to call around.
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Re: 9" rear end lengths for axle swap

Post by averagef250 »

I have no idea what Ford's rhyme or reason was for using the 31 spline big bearing 9 3/8 axles under bumpsides.

I've owned a couple of them in 70-72 F-100's. All of them were fleet ordered trucks and had the highest GVW package with 360/T18's/3.50 gears and a trac-lok. I've seen many more semi-floater dana 60's under bumpsides and they were used under lighter GVW pickups and 4x4's.

The bumpside 31 spline 9 inches use a completely different housing, pumpkin, gears axles and axle bearings so I cannot see how if you found just the axles you could swap them into a 28 spline small bearing housing. The easiest way to tell if a bumpside has one of these is the housing is much larger than the standard one. The weld where the tubes meet the center housing is almost at the spring perches whereas the standard 9 inch has a smaller center section and tubes extend all the way up to it.

I can't recall what happened, but one of the axleshafts got damaged when a wheel bearing let loose on my in my 70 F-100. My only option was to reuse it or have one made for $$$. I couldn't even just call up dutchmans and have them plunk one out for me, I had to bring the axle down to them so they could copy it. They told me they'd never heard of a 31 spline 9 inch under a truck before 73 so I'd imagine they're pretty rare (not sure how I've run across enough of them to make me think otherwise though).

I absolutely pummel the 28 spline small bearing rear in my 74 Ranchito. It's welded up, the carrier bearings are pitted and the housing is too hot to put your hand on after a dozen mile cruise. It refuses to let loose so far though. The car has a factory 4 link coil rear, sticky wide tires and takes some really stupid abuse like 460 valve float reverse-1st drops and it's seen 60 MPH accidental shifts into reverse several times. The Ranchito weighs about 3500. I'd say 28 spliners are adequate for most on road uses. I've broken a pickup load of them in an EB on 36" boggers though, so wheeling is not thier thing.
1970 F-250 4x4 original Willock swivel frame chassis '93 5.9 Cummins/Getrag/NP205/HP60/D70
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Re: 9" rear end lengths for axle swap

Post by NUTNDUN »

I don't know what I want to do, if I could find someone to weld my center up I would do that for now. The motor should be right around 600 horse without the giggle gas. I don't plan on going to the drag strip too often, maybe once a year and I would probably just run on street tires anyway, makes it more fun LOL.
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Re: 9" rear end lengths for axle swap

Post by Salt-shaker »

Good-afternoon, Averagef250 is the "Man" and has Helped me very-very much..He is correct the 9 3/8 is a different animal, however it will bolt into a std housing with a small half moon ground relief notch where the ring gear passes into the case. A quick check of the gasket between the regular 9 inch and 9 3/8 will show the same mount pattern, you can also use the gasket to position the relief notch. My gear set was the 4.09 and I street raced them for years..The axles will also fit, and of course you don't have to use the 9 3/8 housing if do not want to grind the reliefs, the axles I currently own will fit any 31 spline 9 inch truck housing such as a N case which I used years later..As I remember my axles and pumpkin were out of an earlier model truck than listed in the posts above, perhaps there was a bearing change but mine used the std large truck bearing and retaining plate. I know they were available but the specific application I can not remember as they were salvaged over 20 year ago..
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