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"
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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.
