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Do all Ford 9 inch limited slip differentials use 31 spline axles? I think the unit  is out of a 66 Ford station wagon. I have a bad wheel bearing in my 57  and have a set of 28 spline axles with new bearings on them I would like to use and save some money.

They come with either 31 or 28.

  Vic Correnti

Thanks Vic, I guess I'll have to pull the axles and count the splines. 

Check this page. K don't know if this works on all 9" rears but it might help. Chuck
http://www.metropartsmarket.com/rearend/measure.html


Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

Wow, thanks MoonShadow, big help

The 28 spline posi is actually stronger as the larger diameter of the 31 spilne axle thins out the carrier bearing area and they tend to break.the clutch hemisphere.
Yet they did make a centre section which housed a larger carrier bearing too.

CK,
    The posi may be stronger, but the axles are not. The idea of the 31, 33, or 35 spline is to increase the diameter of the axle itself. Allows it to transmit more torque without twisting. The additional splines make that interface stronger as well.
        You are correct about the large bearing housing, it is stronger than the small bearing housing for a number of reasons. 

Frank/Rebop

Bristol, In ( by Elkhart)