Rear axle shaft identification questions

[tpj71mach]

I was wondering if there is some way to determine, without removing them, if the axles in my rear differential have 28 or 31 splines. I have been told by friends that are "Ford guys" that because my car was an H-code with an open case 3.00 rear differential they are definitely going to be 28 spline axles. Is this true, or are there any identifying marks on the axle hub or ID tag or some other way that I can verify the spline count?

My goal is to order a new center section with limited slip and 3.25:1 gear ratio and was hoping to be able to order the center section and axle seals and bearing before I disassemble the rear end. If anyone has any suggestions, I would appreciate any guidance I can get.

The other question is, can I change the axles to 31 splines, or do I even need to? Speedway has axles for around $250 each which isn't cheap but if that is the better way to go now would be the time as I could buy the 31-spline center section to match. I don't know that I necessarily need the bigger axles as my car has only 437HP and 451 lb. of torque at the crank, and I am not planning to race it. I am only inclined to do it because if there is a better option I usually want to go that route for some reason. My motto since high school has always been if you're going to be a bear, be a grizzly, ha-ha. There is no legitimate reason to overkill other than I tend to err on the side of overbuilding as a habit.

Another thing that I don't know since this is my first 9 inch rebuild since the one in my 73 Mach 1 I had in high school. They are listing different length axles, they offer 24 1/4", 26" and 31" and all state they are guaranteed to fit my 71 Mustang. Are the axles different length left to right, or are there different width differentials offered in Mustangs? I thought it might be based on the rear brake size like a 12 bolt is, the wider brake shoes had a longer axle shaft to position the drum properly, but I am just guessing on that.

Also, they offer big bearings or small is there a way to know which you have and are they case specific, or can you upgrade from one design to the other if one design is better?

Sorry, I know I am posing a lot of questions, but I know there are a lot of guys here that know a ton about these differentials. I am hoping to pick your brains as I am really in the dark on this and want feedback from those who know before I start buying parts, thanks.

 

[giantpune]

If I'm not mistaken, the axles slide out without taking the rear cover off. Unbolt the retainer behind your hub and slide each axle out. Then you can measure it and count the splines. Thats a lot easier than accidentally ordering the wrong part and having to send it back.

And wanna say all ours are the small bearings, driver's side is the 31 inch, passenger side is 27 and some change.

You can change to different spline count if you buy a new carrier. The axles and the carrier need to match.

In your screenshot of your shopping cart, those bottom 2 axles say "cut to fit". Of coarse its guaranteed to fit, if you have to use power tools to cut it to the correct length.

 

[CandyRcode]

Yours are 28 pline. The drum pilot design tells me that. 31 are not necessary. You will need to hook it up and rum 11's to consider them. Lenghts are 31 13/16 and 27 7/8th. Most likely your case is big bearing. Big and small bearing cases are not importatnt with your application.

 

[Sheriff41]

Yep, you can generally tell by the exposed end of the axle (drum pilot, as @CandyRcode correctly states); there are some rare exceptions. With the 31-spline there will be two small holes in the end, while the 28-spline have the large indentation like in your pictures. Changing to 31-spline is possible but for a cruiser, not necessary and just added money spent.

I ordered from Quick Performance <https://www.quickperformance.com/> and they were helpful in getting me what I needed. Also, 8and9inchfordrears is a popular source with a track record of being very helpful <https://8and9inchfordrears.com/8"-ford-third-members> and their site has some informative pages.

EDIT: https://metropartsmarket.com/rearend/measure.html

 

[Hemikiller]

Your axles are 28 spline.

As far as the Speedway listing, you're showing a number of "cut to fit" axles. I bought mine from Strange, I should have the spec sheet around somewhere.



The axle ends are a good way to identify the spline count on a Mustang/Cougar or Torino/Montego axle. It *does not* apply to other car lines. IE: the T-bird and full-size axles have the "three holes" pilot of the 31 spline axle but are 28 spline.

31 Spline axle

 

[basstrix]

The image is the end of a 31 spline axle. In a car application, this style has a high probability of being 31 spline, but I've found numerous exceptions in truck axles.

 

[basstrix]

Your axles are 28 spline.

The axle ends are a good way to identify the spline count on a Mustang/Cougar or Torino/Montego axle. It *does not* apply to other car lines. IE: the T-bird and full-size axles have the "three holes" pilot of the 31 spline axle but are 28 spline.

31 Spline axle

You beat me to posting a picture. Good into on the different car lines....I've seen lots of exceptions on truck axles.

 

[tpj71mach]

Thanks to all for all of the great information! Now that I know they are 28 spline axles I can order up the center section for 28 spline axles and be done. I don't feel I will ever need the 31 splines as this car won't be raced and if I were to race it, it surely will not run 11's.

So, am I correct in understanding that our cars have the smaller axle bearings then?

This is not as big of a deal as the center section. I can get axle bearings and seals from the local parts store, but if I can determine which bearings to order first it would be better to get the right ones the first time around.

 

[CandyRcode]

bearing RW207CCRA Seal 9569S Get seals from orielly. They are red. If the seal is green it will leak (cr). The bearings are all junk. China. Try to find KOYO wheel bearings. Those are Japanese. I suggest checking your wheel bearings and see if good. The originals are the best.