28 or 31 spline rear in 69 Mach??

[dkm004 11]

Guys, I have an M code 69 Mach 351W FMX with a 9" rear and Im about to order a new posi rear to replace the old open diff. My question to you is, did these all come with 28 spline, or is there any chance that its a 31?

 

Cheers!

Edited May 13, 2014 by dkm004

['70MACH1 10]

Factory auto has 31 and 4spd has 28.

[RPM 1,190]

My 351w fmx mach one San Jose car has 28 spline. Usually 28 spine has an oval recess in the axle center, while the 31 spine has two holes. Your warranty tag on the drivers door should have the axle code, if the door hasn't been replaced or the rear hasn't been changed.

 

 

Bob

Edited May 13, 2014 by RPM

[ashleesmach1 28]

My mach1 m code had 28 spline with an FMX auto so my bet is you have 28 spline. Once you get the axel out you can count the splines

[dkm004 11]

My 351w fmx mach one San Jose car has 28 spline. Usually 28 spine has an oval recess in the axle center, while the 31 spine has two holes. Your warranty tag on the drivers door should have the axle code, if the door hasn't been replaced or the rear hasn't been changed.

 

 

Bob

 

My warranty tag says that the axle code is a 9. Im not clear what that would be as far as splines?

[69gmachine 15]

It didn't come with a 31 spline rear, but unless you're the original owner, there's always a chance someone has replaced it. Just check the axle hub end. If it has a recessed squared oval in the center it's 28 spline, if it's solid with 3 holes drilled out they're 31 spline (of course this only applies to original ford axles).

[RPM 1,190]

Doh! The 9 axle code only tells you it's got 3.25:1 open, not the spline. 3 holes not 2, I knew that. The center one is from lathe work. Some 3 hole ends are 28 spine, my brother has one. I didn't believe him, so I counted them. My money is on 28 splines.

 

 

Bob

[Guillaume69 150]

If you crawl under the car and manage to see what's on the tag attached to the rear end (provided there still is one), then you'll find out exactly what you have back there. That's how I figured mine was 28, as I didn't know the trick about the ends differences.

[SA69mach 39]

this webpage may help. It has pics of the common 28 and 31 spline axle ends for comparison.

 

http://www.metropartsmarket.com/rearend/measure.html

[maxum96 32]

Factory auto has 31 and 4spd has 28.

 

Where did you get that info? The only factory cars with 31 spline axles that I have ever seen, read or knew about were big block cars (i.e Cobrajets, Boss 429, etc) and Boss 302's. The type of transmission made no difference on the rearend.

[ashleesmach1 28]

your correct maxum96

[dkm004 11]

this webpage may help. It has pics of the common 28 and 31 spline axle ends for comparison.

 

http://www.metropartsmarket.com/rearend/measure.html

 

Perfect...thanks for that, 28 it is!