Here's my first post - been a "fly on the wall" for several months now, after researching the variety of small 4x4s (Samurai, Toyota pickups, etc) to find something "capable on a budget". The Sportage won the contest - I bought a used '97 Sporty from a local college student who was moving back to Brazil & didn't want to pay $50K in import duties & taxes to take it with him. And, lucky for me, he had already lifted the body and suspension (UYK) like I was planning to do, had I found a good deal on a stock rig.

Intros aside, my first big project is to swap out the differentials. I was bummed to find out the new TrackFinder Lockers aren't compatible with the early-version diffs (and they aren't readily-available in the U.S.). But I was inspired by the various posts on using Mazda LSDs (RX-7 & Miata) - specifically this one: Jen's Sporty. After doing a good bit of research on the compatible clutch and torsen diffs from Mazda (stock), I found myself getting frustrated over prices, availability and the fact that most units are used, with the wear & remaining service-life being a big unknown.

That led me to look at the aftermarket options for a new unit. I looked at Eaton, Quaife, etc, only to be deterred by the big price tags for each. <img src="/forums/images/graemlins/zombie.gif" alt="" /> Then I came across some obscure threads on the Miata forums discussing helical-gear LSDs made by OBX Racing (U.S. company - parts made on-the-cheap in China). There were lots of posts bashing these diffs, but also a few that were positive, detailed and seemingly-credible. And the consensus of the satisfied users was that a simple dis-assembly, clean-up/deburr and replacing of the factory case-bolts and Belleville washers makes these diffs "bulletproof". As for cost, these diffs sell for $279 each on eBay (Miata-type: '94-'05). And that was too tempting for me. So I bought 2 diffs to replace the stock-front & rear units on my Sporty. The grand total for 2 diffs, shipped, with sales tax (all of the eBay sellers are based in Oakland, CA <img src="/forums/images/graemlins/angry.gif" alt="" />) was... $652.41 USD. And that's about the price of a new Eaton diff for the Sporty, which was the cheapest-new-aftermarket diff available (and scarce/out-of-production, a clutch-type, with no rebuild kits available, as far as I can tell). I really wanted a torsen/gear-based diff, just for strength, durability and simplicity. The OBX diff fit the bill... and for less bills, to boot!

The other bit of trivia about the OBX diffs is that, despite the marginal machining-tolerances, they are pretty strong. I've found a few posts stating that they've been used in some beefy mod-vehicles with great success (Honda S2000, RX-7, Miata, Ford Focus & Mini Cooper). And some of these cars are said to produce 500+ WHP and didn't break the OBX diff. So I'm hoping that a stock Sporty wouldn't be too much torque for them to handle, even while 4wheelin'. <img src="/forums/images/graemlins/scared.gif" alt="" />

Here's some links to OBX-related threads, if you're interested...
Miata Forum Thread
How to "bulletproof" your OBX diff
Another "rebuild your OBX" site - This guy sells stronger bolts & washers as upgrade kits, which I also bought for mine, out of convenience...

That said, I know that I'm treading into new territory by trying the OBX diffs for off-road use (4x4), and also being the first to try the Miata-spec'd OBX diff in a Sporty (front & rear). So I'm fully-aware that I could be heading for disaster, while fully-unaware what disaster(s) I might/will encounter. That's one of the reasons I'm posting here about the project: I'm going to need some support (technical <img src="/forums/images/graemlins/notooth.gif" alt="" />, emotional <img src="/forums/images/graemlins/baby.gif" alt="" />, etc). And I want to document the process & outcome for the Sporty community ("you can do this!!!" <img src="/forums/images/graemlins/smile.gif" alt="" />... or, "you DON'T want to do this!!!" <img src="/forums/images/graemlins/zombie.gif" alt="" />). And, by the way, I'm planning to do the work myself, primarily because I've asked two different shops for an estimate of the labor-cost for both front & rear diffs - parts provided by me. The first guy quoted me $1500 for labor alone, which I laughed at (violently). And the second guy wouldn't touch the job unless he sold me the parts... which he said was required for his "warranty". Maybe I should offer to sell him the parts for $1 so he can sell them back to me for $2?!?

OK - Here's the first set of questions...

I'm going to install new carrier bearings on the diffs. But I still haven't ordered them. I was looking for the parts at RockAuto, but was a little confused by the variety of bearings & different sizes listed under "differential bearing" for the '97 Sporty. I think this is the correct bearing, because it cross-refs with the 2nd gen/non-turbo RX-7 & '94+ Miata (NATIONAL Part # 32008)... Can someone confirm this? And is there a more affordable-alternative that is still reliable???

Tools: I'm trying to figure out what I'll need to do the job. I figure a jack, jack stands and an impact wrench are required (beyond standard wrenches, sockets, hammer, duct-tape & band-aids). But I've never pulled a diff before. So if anyone can note other "you really need these" tools for the job, that would be much-appreciated! <img src="/forums/images/graemlins/kewl.gif" alt="" />

Circlips: I'm going to order the thinner circlips from a local Mazda dealer (Mazda M005-27-421, as noted at the end of the Mazda LSD-install thread, just in case. Can anyone provide some basic info on the circlips, as far as function, remove/install & how to avoid destroying them while removing/installing the diffs?

That's all I have for now. But before I forget, I wanted to thank everyone for building such an open & informative forum - much appreciated... <img src="/forums/images/graemlins/patriot.gif" alt="" />


1997 Sportage 4x4, auto-trans, Warn manual hubs, 4" UPYOURKIA front lift, TJ 106AA rear springs, 2-5/8" body lift, 31x10.50 treads, SmittyBilt SRC front and XRC rear bumper, swing-out tire mount, OBX LSD front diff, Track Finder rear locker, 5.38 R&Ps and... really crappy gas mileage! <img src="/forums/images/graemlins/shiner.gif" alt="" />