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Discussion Starter · #1 ·
on a Ford 9 inch, is there a way to tell if it is 28 or 31 spline without disassembly?
 

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Yes, almost always the axels have two holes in end towards the wheels for a 31 spline axels. 28 spline have a rectangular dish cut out on the ends of axels. That is an easy way to tell.
 

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spent most my life working in the junkyard..have never seen this method fail...
It not full proof, but most of the time it works. There are exceptions. If you want to see a 28 spline 9" with the 2 hole pattern, check out a 57-59 full size Ford.
 

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I hate to say it, but I've got a 63 Galaxie with 28 spline axles,.....(that's all that was available then), and they have two round holes in each flange.

Also have a 72 F100 9" with 28 spline axles with two holes in each flange.
 

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Discussion Starter · #8 ·
well, I didn't want to rip the rear end apart to count splines so this was great help. I am hoping to find a center section already setup with a limited slip posi. something i could just bolt in. not sure if i care what gears are in it, although i dont think i'd want anything over 4.11 the way gas is. I have 3.00 in it now and get around 18mpg which i'm happy with, but since I only drive it about 3000 miles a year, gearing isnt too big a issue.

I didnt want to rip mine down since i am still able to drive it. not going to touch it till i have what i want ready to go back in.
 

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If it's still there (and most are), post the info on the metal tag that's under one of the center-section retaining nuts. We can often decode it for exactly what it is. Look carefully, as some numbers or letters are often partially hidden under the edge of the nut.

David

Example of a 9" rear axle tag:
 

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I always thought my 65 was pretty stock with a 28 spline. Would this pic indicate it is a 31?
 

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I always thought my 65 was pretty stock with a 28 spline. Would this pic indicate it is a 31?
No. From what I have seen, the 31-spline dimples vs the 28-spline rectangular dish was not a reliable indicator until 1966 or 67. Production methods apparently changed around that time (see 28-spline re-design below) and there were a couple years of overlap where dimples could mean either. However, the rectangular dish always means 28 in every case I've seen.
Which is better, 28 0r 31 and WHY ?
Neither is "better" for most stock applications. However, HP and HD applications can use the greater strength of the 31-spline, which is generally rated roughly 20% stronger in both flex and twist (bending and torsion) than the 28. In HD load-carrying applications (trucks) the axle size also changed the axle housing tube size and thickness for greater load, as well as often including a larger flange (wheel) bearing. Just beefier all-around.

So, you can see that changing the axles in your car's housing from 28 to 31-apline will not increase the HD load capability much on it's own, but will increase the HP torque capability for higher horsepower. Along these lines, it's interesting to note where failures happen, as high shock load (manual launches with slicks) even at fairly low power tends to twist or break the axle at the splines where it enters the gear carrier, whereas cars with brute power twist their axles along the length.

This is interesting as it relates to the overall increase of both power and weight through the 1960s, from typical 6-cylinder cars to later years where mid-size V8s were standard in many models. In these later years, the 28-spline axle was beefed along it's length for the reasons stated above, and are significantly stronger than earlier versions for handling torque in the more powerful and heavier cars. If they had not beefed the 28-spline design, we would have seen far more cars with 9-inch 31-spline axles as standard. HTH

David
 

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well, I didn't want to rip the rear end apart to count splines so this was great help. I am hoping to find a center section already setup with a limited slip posi. something i could just bolt in. not sure if i care what gears are in it, although i dont think i'd want anything over 4.11 the way gas is. I have 3.00 in it now and get around 18mpg which i'm happy with, but since I only drive it about 3000 miles a year, gearing isnt too big a issue.

I didnt want to rip mine down since i am still able to drive it. not going to touch it till i have what i want ready to go back in.

Better to check it now than to take a chance on getting the wrong punkin. Jacking up one side of the car and removing the wheel and one axle doesn't take that long. Chances are you will guess right with the info given, but there is always the chance you won't. It'll cost you a new axle gasket and an hour or two.
 

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Better to check it now than to take a chance on getting the wrong punkin. Jacking up one side of the car and removing the wheel and one axle doesn't take that long. Chances are you will guess right with the info given, but there is always the chance you won't. It'll cost you a new axle gasket and an hour or two.
+1. Remember, it only involves removing the wheel and drum, and then four nuts to pull the axle. That's it. You could be counting splines in 10 minutes. My 2-cents is that it would be worth the peace-of-mind when you're talking big money or big frustration for a mistake. Think of it as a practice run, and a check for if you will need an axle puller to get them both out later. Some stick, some don't.

David
 

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I have a 3.5 pumpkin, is there a way to check the number of splines in it?
 

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I always thought my 65 was pretty stock with a 28 spline. Would this pic indicate it is a 31?
Mine's the same and they are 28 splines.

James, why not go ahead and pull an axle? It's a very simple job, you could have it apart and back together in 30 minutes and then you would know for sure. Even if you have a stubborn one it shouldn't take much longer than that. Mine had never been apart and I was surprised at how easy it came apart the first time I pulled an axle.

Here's a simple step-by-step procedure for you:
-Crack lugnuts loose
-Jack car and support with jackstand(s)
-release parking/emergency brake, put car in neutral
-remove wheel
-remove brake drum
-Use a deep 9/16 socket through the hole in the wheel flange to remove four nuts from axle retainer
-place brake drum backwards on lugs and put on three lug nuts about half a nut deep
-use the brake drum as a slide hammer against the lug nuts to pull the bearing loose from the housing
-grab a rag and slide the foul smelling, sticky nasty thing out of the housing
-wipe it down good and check/measure/count etc.

It goes back in just as easy, just have to wiggle it around a little and it will drop back into the splines in the differential and should slide in without hammering but you could hammer if it's stubborn. put the retainer nuts back on, brake drum, wheel, let the car down, make sure your lug nuts are torqued down and you're done, piece of cake.
 

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I agree there is only one way to know for sure what your spline count is. Pull the axle and count. Unless you have a big block performance car it's probably 28 spline. Pull it!
 
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