"Dear Diary"... I stopped by the local 4x4 shop (where I bought my Smittybilt bumpers) and had a chat with the boys about my dilemma with the rear diff... and how I've painted myself into a corner... and that I'm determined to make something work, even if I have to stand on one foot while the paint dries - so I can switch to the other foot and finish the job! <img src="/forums/images/graemlins/shiner.gif" alt="" /> And from my discussion, I've narrowed down a few options...
A) See if the Lock Right locker for the Ford/Mazda 7.5" open diff is compatible with the 28-spline Sporty axles. The guys are having the part shipped in tomorrow morning and I'll stop by with the stock diff and a 28-spline axle for a test-fit. I doubt this will work because the Ford splines are reported to be 1.2" diameter, which is just over 30 mm. The Kia splines are 29 mm. And then the side-to-side spacing inside of the carrier would have to match too. But it's worth a try...
Estimated cost: $400
B) Had a desperation-induced epiphany at yesterday: The OBX diff is a 2-piece case. The only dimensional-difference between the stock rear-diff and the Miata-spec'd diff is the size of the ring gear mount (mounting flange and case diameter where the inside of the ring press-fits). The bearings are the same and the end-spacing is dead-on. So... I could have the ring gear-side of the OBX casing duplicated with the case diameter and ring mount modded to fit the 7.5" ring gear (i.e. have a new part machined). That would allow me to use the OBX gears + the other half of the case. I know that will work, as long as the machining is good... or at least as good as the Chinese-version of "quality control". <img src="/forums/images/graemlins/zombie.gif" alt="" />
Estimated cost: Unknown
C) Buy an Eaton LSD for made for the Sporty. The guys at the shop are looking into it and said they'd sell it to me at cost if they can find one. Their supplier said the 28-spline Eaton LSD (#19536-010) is still active in their parts-system, even though Eaton has discontinued them. They also said that if the "Just Differentials"-dude on eBay can get them, they shouldn't have a problem (they used more colorful phrasing while stating that... <img src="/forums/images/graemlins/notooth.gif" alt="" />). They also said the Eaton clutch-type LSDs are pretty solid and would probably last longer than I'll abuse the vehicle, as long as I don't spin a wheel in the air and slam it down on the ground (tends to destroy the clutches, they say). Again, another option that will work if the part can be found.
Estimated cost: Less than $699...
D) Try to get a Track Finder locker made for the 28-spline open carrier. That will work, for sure. But I haven't heard of anyone getting one shipped to the U.S. - If you have, let me know...
Estimated cost: Over $700 for the part, plus shipping and possible import fees... <img src="/forums/images/graemlins/rolleyes.gif" alt="" />
Yep, that's where I'm at right now. Oh, I went back through the "
Jen's Sporty" thread. After reading several times before buying the Miata-spec'd diffs and several times after confirming the 7.5" ring gear isn't compatible, I still get the impression that she installed 2 second-gen big-axle non-turbo RX-7 diffs in her Sporty. But she also commented that she did the welding, which I now wonder if it alludes to Lincoln-locking an open carrier (rear). I don't know. And she never responded to my PM through this forum. The other possibility is that she installed a Mazda LSD in the rear using a front pumpkin bolted to the rear axle housing. From other posts related to this topic, it sounds like the rear pumpkin will bolt onto the front axle housing. But that would mean she's running a 7" ring gear in the rear. What's the drawback with that? Anyone??? I'll add "test-fitting the front pumpkin on the rear axle housing" to my list of things to check out... <img src="/forums/images/graemlins/baby.gif" alt="" />
