8.8 28/31 spline count question

juice90 · Jan 26, 2016

got a 1994 mazda B4000 4x4 with an 8.8 28 spline trac loc in it. I am still looking for a new set of spider gears and 28 count seems rather hard to come by.

I do believe I read both on here in the axle section and on a parts web page that I can use the 31 spline spider gear kit in place of the 28 spline. Is this correct? I just want to confirm before I commit to buying a spider gear kit.

Thanks

mkyhmltn · Jan 26, 2016

If you put 31 spline spider gears in there you would also have to go to 31 spline axles. 28 spline spiders for a trac loc are hard to find.

Here is a set'

http://www.ebay.com/itm/OEM-Ford-2L1Z-4215-EA-Differential-Pinion-Gear-Kit-Ford-Lincoln-Mercury-NEW-/161933262001?hash=item25b3f97cb1

4x4junkie · Jan 26, 2016

Isn't the Mustang 8.8" (non-Cobra) 28 spline? Might be able to use spider gears from that (certainly the entire carrier could be swapped).

I believe the 31-spline 8.8 carrier is different than the 28, so the gears will not swap if so (and yes, you would need to have custom axle shafts made with the smaller size wheel bearing journal).

adsm08 · Jan 26, 2016

IIRC, and I may be out in left field here, the spider gears, the ones the pins go through, are the same 28 or 31 spline. The side gears, where the axle shafts go in, are definitely different.

4x4junkie · Jan 26, 2016

No the smaller spider gears are different too... Gears for a 28-spline have a 3/4" pin bore, 31 spline has a 7/8" bore.

mkyhmltn · Jan 26, 2016

4x4junkie said:
No the smaller spider gears are different too... Gears for a 28-spline have a 3/4" pin bore, 31 spline has a 7/8" bore.

Correct. Also while in there it would be a good idea to replace the LSD clutches, which are the same for 28 or 31 spline.

juice90 · Jan 27, 2016

Ok thanks guys. That's what I thought. The reality is, I only need the two smaller gears, as the side ones are perfectly fine. The trac lock clutches were worn right out and the tabs started breaking off and went through the gears, and chipped only the small gears badly, but left the side ones alone.
And I didn't want to pay big dollars for the Yukon gears.
Seems rather odd, that with the popularity of this diff, having been used so much, that 28 spline sets are not readily available. But i'll try that set from the ebay add that was posted by Mkyhmltn.

AllanD · Mar 15, 2016

The "Spider" gears are the same in open diffs.

8.8 28/31 spline count question

juice90

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