Rear Axle Help!

[70grande]

So I have a 1970 Mustang Grande and my drivers side axle grease seal and bearing blew out, so now my car is making a clicking noise, leaking axle grease everywhere and I need to get it fixed ASAP. I busted out my NPD Catalog and went to the axle section only to find that there are 3 different rear axle grease seals for 70's.
The first is for 2 5/6" O.D., 7 1/4"
The second is 2 17/64" O.D., 9" w/31 spl
and the third is 2 17/64" O.D., 9" w/28 spl

How can I figure out which one to buy?

 

[ForceFed70]

Well, you need to figure out what rear axle you have.

The 31 spline 9" is called the "Big Bearing" version. Unless you have a car that came with a big block, it's unlikely you have this axle.

If you have a V8 engine, it's unlikely you have the 7 1/4 rear alxe.

There's lots of pictures out there for info on how to identify your rear axle. I'd start by figuring out if you have the 9" axle or the 7 1/4.

Also, these seals are readily available at your local autoparts store. It might be easiest to buy 1 of each and then return the seals you don't need.

 

[tx65coupe]

If he has a V8 then most likely it is an 8 inch or a 9 inch. I didn't think the 70 Mustangs came with the little 7.5 even with the 6 cylinder.

I bet you have an 8 inch.

Does your car have the stock rearend?

Take a look at these rear axle ID websites. Maybe it will help. These are pages I found when I swapped in a 9 inch Versailles.

Kevinstang's Ford Nine Inch Differential Page +

Rear Axle

 

[96 DOHC Cobra]

390 FE Mustangs came with 28 spline axles. Boss 302 Mustangs came with 31 spline axles. What rear originally came in your car? Does your car have the original rear in it? Unless your car was a factory high performance model or someone swapped in a 31 spline Mustang rearend, it's 99.9% most likely a 28 spline small bearing seal. The last time I needed one of these, I just went to Pep Boys. Faster and probably cheaper than shipping from NPD. It was 1/2 of what theFord dealer wanted when I checked with them.