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Discussion Starter · #1 ·
I have a nine inch rear that is a 31 spline and posi. I would like to put this in a car I'm building. It bolts in fine but is an inch too wide on each side. I have been told that the axles shafts can be cut down on 31 spline axles. My ? is would they need to be cut down for only an inch or could I just let them sit in an inch farther. Also would there be enough of the spline left or would I need to get them resplined also?
 

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How about wheels that have 1 inch more back space?? just a suggestion.Gary
 

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Discussion Starter · #3 ·
Right now I have test fitted a 14 by 7 wheel with 4" backspacing and it is too close to wheel well, so I need to shorten rearend.
 

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I did this on an I6 rear end. It was just to see if I could and because I had wheels that rubbed. If you shorten the housing the axles will push in . There might be enough spline but what I found was that the axles will hit the cross pin. I shortened the rear 3/4" on each side and had to cut a 1/2" off the ends of the axles before they would fit. I also had to extend the splines a little. A cutoff tool is great.

My suggestion get new wheels or the correct housing.
 

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Here's what I would do....

Take the rear end out of the car but leave the springs in. Put the wheels and tires into the wheel wells where you want them, carefully checking for clearance in all relevant areas. Once finalized, measure between the inner flange surfaces of the wheels.

Then, take that dimension and your bare housing and axles to a local machine shop that does rear end narrowing and get an estimate on making the housing and axles the correct width. A shop which does this often will have the jigs to do the housing and the cutters and dividing head to do the axles.

I run 31 spline axles in the race car which are substantially narrowed (about 10" total). IME, the 31 spline axles I've seen have sufficient diameter to re-spline or extend the splines. I did many an axle the old-fashioned way, in the lathe with a correctly angled cutter turned on its side. Kind of like a horizontal broach. Time consuming but inexpensive (compared to 1 to 2K for a dividing head and cutters). It's important that the area being re-splined isn't too much larger in diameter than the original splined area as machining the area could weaken the case hardening of the axle.

IMO, don't take any short cuts when doing this, if narrowing is what you want to do. You can't just cut axles off and stick them in. I know ways of cheating in this area but none of them are good for long-term reliability.

Another option, although it affects driveshaft location, would be to consider running two short side axles and narrowing the housing to the correct length. It might be a bit more than 2"; I can't recall. Of course, you'd need two short axles *G*. The spring pads would need to be moved because of the way the housing has to be narrowed.


Hope that helps!
 
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