I have verified that the splines on the 28 Spline Rear axles are larger than the 26 splines. No precision measurements yet but it is aproximatly 28.5 or 29mm.

This does look positive for Mazda RX-7 Turbo LSD's fitting the Sportage and possably ARB having the tooling for splines to make a locker for our [color:"blue"] Rear [/color] axle.

What I have found out is that the non-turbo RX7s have a 7" ring gear and the newer (85+??) have the same splines as our front diffs.

The turbo RX-7s have a larger ring gear and MIGHT be the same size as the Sportage REAR.

It seems that the Turbo RX7 is a 30 spline diff.

Are we sure that the Sportage rear axles are 28 splines not 30 splines? Much of the RX7 specs seems to be just repeats of old info that may be wrong. Could our 28 spline rear info be wrong too?

No disrespect, but you seem to be contradicting yourself.

The other issue is that axle diameter does not always equal spline diameter, this depends on whether they are rolled on or cut into the axle ie

___/--------| rolled
.................|

or
____________
....\---------| cut
..................|


where:
------ = spline
....... = metal
_____ = edge of metal (axle diameter)

G'Day Gary,

I don't think that I have contradicted myself but is kind of late here. The contradiction seems to be some info on the web.

We do have verification of the size of the Sportage 26 spline FRONT diffs and ring gear.

We DO know that the splines of the REAR axles that have been called 28 spline axles have larger diameter than the 26 spline ones.

We also know that the REAR axle shaft is larger than either spline diameter. I have the figure somewhere but I think it is around 32mm.

What I have not been able to verify is whether the 28 spline axles really are 28 splines or are they 30 splines.

Also with Mazda and Kia's part numbering methods, we can't really tell if the rear Sportage and rear RX7 TURBO ring gears are interchangable.

All we really know is the Sportage REAR diffs and the RX7 TURBO REAR diffs are larger than the Sportage FRONT diffs and the Sportage FRONT diffs are nominally interchangable with the 94+ Miata REAR diffs and the RX7 NON-Turbo 26 spline REAR diffs.

At this time we can only speculate that the Sportage REAR diff is the same size (but possably different splines) as the RX7 TURBO diffs. The only source of info on the RX7 TURBO axle splines is SoloMiata's site which states 29mm x 28 splines but both of the RX7 Turbo diffs on ebay are reported to be 30 splines by their sellers.


Just had a thought: I wonder if the Sportage rear splines are actually 30 splines with 2 splines 180 degrees apart removed?

What we really need is someone with a newer rear axle or diff out of the vehicle that can do some counting and measuring.

when i used to talk to Jeff at Eaton, he verified the 98-04 rear axle had 28 splines. he didn't say anything about a gap between any of them, so i doubt that's the case. we have also heard from solomiata that the rear diff is a 7.5" ring gear, not an 8" ring gear and as can be seen from looking at the housing, it is not as large as a toyota 8" housing so it is safe to say, the ring gear is prolly not as large as the the toyota 8" ring gear, but it is visibly larger than the verified 7" front Kia ring gear, so it is safe to say that the Kia rear ring gear is larger than 7" and smaller than 8". ron, if there is an rx-7 or miata diff that measures 7.5" that may be the one that will work. this is the only reaon i mentioned to look into ford stuff, because the broncoII and ranger rear axle is a 7.8, which is very close to 7.5 and therefore, may be close enough, with light machining to be interchangable. also, from what i have seen, normally, the spline area is actually a larger diameter or the same diameter as the majority of the shaft, not normally larger.

Hi Dave,

Was Solomiata talking about the Sportage rear or the RX7 rear? I have not seen anything from SoloMiata that says the RX7 is anything other than 7" or 8". See here about 1/3 of the way down:
Solomiata Mazda Drivetrain Interchange

------------------
"While the 1990-93 Miata rear had a viscous LSD option, the 1994+ Miata's could have been ordered, based on package, with the superior Torsen type LSD. A poor mans alternative to the Torsen is a clutch type LSD from the '84-88 NA RX-7. They will also bolt into the later 1994+ Miata housing since they are basically the same diff type (the 1989-91 RX-7 LSD will also fit but it is a viscous type, the earlier RX-7's had smaller axle shafts and won't fit). The OEM RX-7 clutch type LSD does have replaceable friction plates and is rebuildable.


According to the literature all 84-85 RX-7's had the large axle. It has surfaced that some 84 12A's with the 3.933 ratio has the "small axle".
7" small axle = 25mm x 24 spline
7" large axle = 27mm x 26 spline
8" = 29mm x 28 spline"
-----------------------

As you can see he only mentions 7" and 8". He also shows the 8" splines as 29mm x 28 splines which is now looking to be wrong.

As far as the Sportage axle shafts, my KIA service manual lists the rear axles as 33mm in diameter. It's not the same diameter or smaller than the splines.

So we still don't know if the RX7 and the Sportage REAR diffs are the same size.

solomiata mentioned it in a post he made here in THIS forum, sure it shouldn't be too hard to find, although, it was at least a year and a half ago.

your 33mm measurement could be the wheel bearing neck-up.



true.

Hi Dave,

I read all 11 of solomiata's posts and couldn't find any info from him about our rears but I did get to put a ruller on a Sportage rear diff today. The ring gear is about 7.5" and the splines are 28. So It doesn't look like the Turbo RX7 rear will fit. I guess the next diff to check is a Montero or a Honda S2000.