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28 or 31 spline?

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Blacktop

28 or 31 spline?

Hi all,
Looking at doing a gear swap in the 9" axle on my '84 short bed.
Will this axle have 28 or 31 spline shafts?
Thanks for any info,
Alan.

1984 F150 XLT short bed 4x4 351w 4speed manual
1980 F100 long bed 2wd 300-6 3speed manual project truck
🇬🇧UK based truck enthusiast🇬🇧

Gary Lewis

Re: 28 or 31 spline?

Administrator

I believe all F150's have 31-spline axles. I'll do more checking

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

85lebaront2

Re: 28 or 31 spline?

Administrator

If it's any help my 1977 did.

Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

Gary Lewis

Re: 28 or 31 spline?

Administrator

Everything I've found says that axle takes the same shaft as all the others, so it should have 31 splines.

Gary, AKA "Gary fellow": Profile

Jacob84

Re: 28 or 31 spline?

I have a 9 inch in mine and it is also 31 spline

Jacob,
84 F150 base model, New 95 roller 351w with 5.0 ho roller cam, Summit Racing Max EFI 500, and other toys, MSD DIS, C6 trans, 9 inch rear 3.50, reg cab, long bed, 4x4. 33s, 2.5" Rough Country lift.

Blacktop

Re: 28 or 31 spline?

In reply to this post by Gary Lewis

Many thanks everyone for your input👍😁

Alan.

1984 F150 XLT short bed 4x4 351w 4speed manual
1980 F100 long bed 2wd 300-6 3speed manual project truck
🇬🇧UK based truck enthusiast🇬🇧

Rembrant

Re: 28 or 31 spline?

In reply to this post by Gary Lewis

Gary Lewis wrote

I believe all F150's have 31-spline axles. I'll do more checking

I always thought it was 28 spline for cars, and 31 for the trucks...at least with the 8.8's it is this way.

1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

85lebaront2

Re: 28 or 31 spline?

Administrator

No 100%, I had a car with a nice factory narrowed 9" with 31 spline axles. I found that for a fact when I ordered a Detroit locker from my local dealer. I also am pretty sure the big block pony cars and intermediates got 31 spline axles along with the Galaxies an Mercury full size cars.

Bill AKA "LOBO" Profile

ratdude747

Re: 28 or 31 spline?

In reply to this post by Rembrant

Ranger and Explorer 8.8's are 28 spline. As would be the Bronco II and Aerostar if they ever had it (wasn't an option on the ranger until 1990, which was partnered with the 4.0 OHV Cologne).

1984 F150: 300 L6, AOD, RWD. EEC IV / TFI, Feedback Carter YFA Carb. Stock everything but radio (for now).

MarkF100

Re: 28 or 31 spline?

This post was updated on .

In reply to this post by Blacktop

From; https://www.vintage-mustang.com/attachments/ford-8-and-9-inch-rear-ends-identification-pdf.766989/
A method to identify 28 spline axle shafts can be by looking at the center brake hub area, a rectangular slot in the center will indicate 28 spline axles. The 31 spline axle shafts will have a different appearance, with one small center chamfer and two outer holes in the center hub, however, 28 spline shafts can also appear like this to, so it does not always indicate 31 spline shafts (see photo below). Early axle shafts of the 28 spline variety cannot be shortened, due to either a reduced diameter between spline end and bearing end (early Mustangs, Fairlanes, Falcons etc.), or because of a tapered shaft which doesn't allow for re-splining (early full size).It appears starting around 1967 the 28 spline shafts became more solid and the shaft diameter increased along the entire length, so shortening is possible and they can be resplined to their original 28 count. Most31 spline shafts can be shortened and resplined with no problems.

Odd that I don't see your tag in this list. http://www.fordification.com/tech/rearends_ford07.htm It might be of use to others, as it was for me.
I don't see where the tag would identify spline count it self.
The 9 inch in my 83 F100 came from a 63-72 F100 and has 28 splines. The tag code is WDM-H

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