big bearing vs. small bearing 9 inch rear

[lethal289]

Is the only difference in the bearing the outside diameter?  In other words, is it safe to assume that the same axle (as long as spline count and axle tube length is the same) could be used in either style bearing housing? 

Theres enough information on the net to really confuse somebody about this.  Ive exhausted multiple avenues in trying to find a 9 inch rear end for my car, I've done plenty of research, and im confident i could modify one to fit.  I even think i could make a jig for checking trueness and straightening if necessary and also for reassembly. However, the housing i've sourced is a big bearing truck housing. I am curious if there is any problems i may run into. 

I plan to replace the 31 spline 5 x 5 truck axles with 31 spline correct length mustang axles. So when i replace the bearing with new, are the axle diameters the same length? 

Any tips, thoughts, ideas, links would be appreciated.  Speak up if you have done anything like this.  Thanks.

[johnpro]

I'm not sure of the answer to your question, but I think the axle is different on the big bearing cars.  Do not quote me on that, though, as I could be very wrong on that.

If you're shortening the axle anyway, though, you could probably use the tubes off your 8" rear and turn a big bearing rear into a small bearing rear.  Then, if you wanted to just stay with a 28 spline you could re-use your 8" axles, or just buy new 31 small bearing axles.

[DougG69]

Is the only difference in the bearing the outside diameter?  In other words, is it safe to assume that the same axle (as long as spline count and axle tube length is the same) could be used in either style bearing housing? 

Theres enough information on the net to really confuse somebody about this.  Ive exhausted multiple avenues in trying to find a 9 inch rear end for my car, I've done plenty of research, and im confident i could modify one to fit.  I even think i could make a jig for checking trueness and straightening if necessary and also for reassembly. However, the housing i've sourced is a big bearing truck housing. I am curious if there is any problems i may run into. 

I plan to replace the 31 spline 5 x 5 truck axles with 31 spline correct length mustang axles. So when i replace the bearing with new, are the axle diameters the same length? 

Any tips, thoughts, ideas, links would be appreciated.  Speak up if you have done anything like this.  Thanks.

If you haven't already, you might check out this site:

http://www.kevinstang.com/Ninecase.htm

Scroll down to the section named "Housings and Bearings, etc." I'm far from an expert, but this page looks like it has some info on the bearings, case taper, backing plates, and shock plates that may help answer your questions.

[65fast]

Have you considered purchasing a "new" housing online?  I picked one up for about $450 with with the correct spring pads and all.  I looked about modifying the housing I had and it was going to be about the same price as the new one I ended up purchasing.

[M66Stang]

Rather than going thru all the trouble in finding a 9" housing that fit in the '66, I just had my new 8" third member splined to accept 31 spline axles and installed the 31 spline small bearing axles like Johnpro said. 

Mark

[lethal289]

If you're shortening the axle anyway, though, you could probably use the tubes off your 8" rear and turn a big bearing rear into a small bearing rear.  Then, if you wanted to just stay with a 28 spline you could re-use your 8" axles, or just buy new 31 small bearing axles.

Ive considered this, but ruled it out for now because i don't want the car to have any down time.  The show season is finally getting started here.

Any idea if I just put small bearing flanges on the 9 inch tubes, would that work?

DougG69, thanks, i've been all through that site already.

Have you considered purchasing a "new" housing online?  I picked one up for about $450 with with the correct spring pads and all.  I looked about modifying the housing I had and it was going to be about the same price as the new one I ended up purchasing.

Yes, but i scored a complete rear end off craigslist for 50 bucks.  After 100 bucks per axle (if i have too), im still $200 ahead after my time, labor, and some welding wire.  :craz  Plus i like metal projects.  

[buening]

The way I interprete Kevinstang's site, the axles are interchangeable in all 8" and 9" rears in terms of diameter at the bearing.  He mentions that earlier axles are tapered but that only comes into play if you decide to shorten an early axle.  I think you should be fine in terms of using any 8" or 9" axle as long as you don't get one of the early tapered ones since you'll likely be shortening the shafts.  If you are getting aftermarket axles, then the shortening issue doesn't come into play  :craz

[pprince]

I thought so too but my 8" axles don't fit the bearings I bought for the 9" Versailles.

I could get other bearings, maybe, but I had already bought bearings for the 9 so I am going to use the Versailles axles. They are actually significantly chunkier than the 8" axles.

[camachinist]

OP, try reading this thread and see if anything meaningful results...

IIRC, I've got a small bearing 31 spline rear in the race car, with a housing from a 57 Fairlane, and it takes a special bearing and seal to make the larger axles work in the small bearing housing. I did this to retain the OEM brakes (lighter) for drag racing, but still have the advantages of the 31 spline axles. I wish I had more specifics but did it 30 years ago so that info is long gone.