31-spline Trac Loc conversion

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What differential? 9 inch, 8.8, Dana?

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I dont think you need to machine anything to fit a 31 spline axle in there. You already know they came with 31 splines from the factory. The axle should go right in as long as the rest of the components are set up for 31 spline.

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i have done this a couple of times... If you have a set of 31 spline side gears lying about for free then it could be worthwhile. Yes on some carriers you do have to machine them out to fit the 31... however, if you have to buy a new set of gears, then you might as well replace the clutch pac while you are there, and then the bearings,,,, etc, etc,,, Better off just buying a new truetrac and getting it over with... The ford Posi unit is not that great to start with... imho...

dkp

JBR-3 wrote:No. The case halves are too small, the hole for the axle where the carrier bearings ride.
Needs to be bored out about 1/16" more diameter.

A 28 spline side hat has internal 1.236", has to be machined to 1.360" to match the 31 spline. The axle won't go through otherwise

Bosshoss said some carriers need to be machined. Forgive my ignorance, as I have never encountered this situation.
I have swapped 31 spline setup's into all kinds of different cases, and the axles always seated in.
So I guess there are some cases out there that were made with the smaller diameter opening, and then it seems like the factory began opening them up to the larger diameter not too long afterwards?

It's kinda like the way early C4 transmissions used a 24 spline input shaft, then switched to a 26 spline later.
Learn something new every day!

JBR-3 wrote:I have a 28-spl Trac Loc.
I know it will depend on shops local to me, but just gauging if I should machine/convert
or just sell it and buy a 31-spl Trac Loc.

You may want to find a friend or family member that has the machinery to help you with this.