4x4Wire TrailTalk

OBX Racing Differentials in a '97 Sporty?!?

Posted By: Peabody

OBX Racing Differentials in a '97 Sporty?!? - 07/09/11 10:26 PM

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="" />
Posted By: ackerman

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/10/11 04:50 PM

Keep us updated on your progress <img src="/forums/images/graemlins/kewl.gif" alt="" /> Post up some photos of ur sporty when u get a chance.
Posted By: Everet

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/10/11 09:54 PM

Did you get your Sporty from Didi?
Haven't heard from him in a while.

Keep us posted on your progress.

Great post!

Everet <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" />
Posted By: Everet

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/11/11 04:13 AM

Quote
So I bought 2 diffs to replace the stock-front & rear units on my Sporty.


I don't believe that they will work on the rear diff. of the sporty.
The ring gear for the rear of the Sportage is larger than the front. To the best of my knowledge, no other carrier fits the sportage rear except a sportage. PLEASE CORRECT ME IF I AM WRONG.

If you can measure hole to hole distance on your OBX and post it.

I have an extra rear carrier that I can measure the distance and will post it tomorrow.

Everet


<img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/12/11 06:13 AM

Everet - Yes, I did buy the Sportage from Didi. He finished his grad program in June and should be back in Brazil now. But he really loved that Sporty, which made me all the more comfortable buying it from him. And he did have good things to say about you and the lift kit.

And now back to the OBX diff...
I did some quick measuring and here are some dimensions that should clear things up regarding the rear carrier, I hope:

- 10 holes on the ring mount, hole-to-hole on the outside edges measures 5.7" and 4.9" between the inside edges (approximate for both). So that should be about 5.3" center-to-center.

- The bearing mounts are 1.575" in diameter.

- The ring mount is 6.06" in diameter.

- And the length of the diff, bearing-end to bearing-end (in-line with the axles) is 6".


I am 95% sure the diff will fit both front and rear. From what I've gathered between this forum and others, the hole pattern should be the same for both the 7" and 7.5" ring gears. I think the difference is in the rings, with the 7.5" being a bit beefier with the extra 1/2" of diameter. And that would jive with the Mazda-boys not being able to mount the 7.5" ring in their diff assemblies, because their housings lack the space for the larger gear & matching pinion, even though the diffs are the same... I think. My biggest concern is with the ABS-sensing ring mounting. I haven't come across any mention of that being an issue/non-issue with the OBX diff for the Miata. So I'm not sure what to expect there.

Looking forward to hearing how the numbers compare... <img src="/forums/images/graemlins/scared.gif" alt="" />
Posted By: DennisThompson

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/13/11 08:54 PM

With all the research I did years ago what I came up with is the rear dif, ring & pinion crosses with the turbo RX7 and the front dif, ring & pinion crosses with the non turbo RX7/Miata. I have both a front and rear carrier out of the axles and the rear is bigger than the front. If you want Friday I can take measurements and pics and post them here. I am sure if the rear factory limited slip would fit in the front someone (me) would allready be running one in the front. If what you bought works, please let us know how well it does off road.

Dennis
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/15/11 06:04 AM

If I understand correctly, the 1st gen Sportages through the '97 model year had 26 spline axles in the front and rear. The non-turbo RX-7s (2nd gen/big axle) are also 26 spline, as are the '94-'05 Miatas. I think the turbos had a higher spline count and are not compatible. I have to say that there's a load of conflicting info on the topic. Perhaps we can clear things up for good with this thread...

To add to the confusion, I called a local Kia dealer and had a chat with the parts guy. I was trying to get the part numbers for the front and rear diffs on the '97 model year. I thought that if they are the same, then that would clear things up. But the guy didn't know the difference between an open diff and an LSD. He couldn't even tell by looking at the diagrams. So after 10 minutes of zero-progress, he said I should come over and check out the parts book myself. I will do that if I can get there before the parts dept closes tomorrow or Saturday.

On another note, I remember finding a few posts in the Front Limited Slip thread. There was a guy from Thailand that said the rear LSD fits in the front diff housing...

"Hello! everybody I'm yuennong from KIA@weekendhobby.com
It,s so easy to modify front limited slip by
1. find the second hand rear sportage limited slip (or buy new one)
2. remove only the ABS sensor gear
3. put (install) that rear limited slip into front axle differietial case ... then your sportage are ready to rock-n'roll."

If you read through the posts, it sounds like the rear LSD fits without issues, and that they swap out "everything" except the ABS ring (not needed in the front). The thread on Jen's Sporty (link above) also notes that the RX-7 LSD fits the front and rear, though the details are limited. And that's what leads me to believe the only difference between the front and rear diff assemblies is the size of the ring, pinion and the carrier housing (to hold the larger gear). Ah, but its all here-say until we put hands on the parts...

Last bit - I ordered the Mazda circlips today. The dealer said they'll be in by Thursday of next week. And I think I'm going on a shopping spree at Harbor Freight this weekend to get some tools I'll need for the job, but don't have (anymore). <img src="/forums/images/graemlins/kewl.gif" alt="" />
Posted By: 2002_Sporty

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/15/11 10:04 AM

Does all this information ONLY apply to the 26 spline front and 26 spline rear Sportage for years '94-'97?

I have a North American 2002 Sportage with ABS.

Can anyone tell me what items to purchase to get an LSD in the rear of my 2002 Sportage?
Posted By: DennisThompson

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/15/11 03:59 PM

I think what I will do is take apart my extra front and rear difs and see what is the same and what is differant, if what you say is right I might be looking for another rear LS to put in the front. I might not get to it today but when I do I will take pics and tell you what I found.

Dennis
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/15/11 10:24 PM

Yep, this bit of Sportage-trivia is only pertinent rear diffs on model years through '97. The '98s and up have a rear diff with a different spline count. I believe the front diff is still the same. So you should be able to swap out the front diff with any compatible type (RX-7, Miata, OBX?). However(!), you can put a TrackFinder locker in your rear diff (open-type), which is a not an option for the 26-spline types. I would opt for a locker in the rear if they were available. Didn't you contact TrackFinder to get a price for the locker shipped to Alaska?
Posted By: 2002_Sporty

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/16/11 08:48 AM

No reply, Lost in translation most likely.
I would love to purchase the locker for the rear.
I just need a solid contact and a place to swipe my credit card. This seems to be the only deterent for me now.
I do not wish to steal this thread. Sorry.
Posted By: logansportage

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/19/11 12:10 AM

The 97 and older Sportages had 26 spline axels front and rear. In 98 they changed the rear to a 28 spline, but kept the 26 spline in the front. You can use the rear LSD from a 97 or older in the front if you can find one, but you will need to do some minor clearencing to keep it from contacting the inside of the case and provide enough room for proper lubrication. You need to check the clearance on both the the end away from the ring gear and also the ring gear itself.

Thanks for the info on the OBX diff. If this really works, then there is an option for a less expensive traction aid in the front for all first generation Sportage owners.

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Everet

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/19/11 03:10 AM

Quote


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="" />



Something else you will need is a dial indicator with a magnetic base (you can get them pretty cheap at Harbor Freight that will be accurate enough)and you will need to read about setting up a rear end unless you're going to have someone set it up for you. It is not complicated but "good enough" isn't. This has to be done correctly or you will have a noisy, short lived project.

The least expensive bearing source I found is <a href="www.blackdragonauto.com" target="_blank">BLACK DRAGON AUTO</a>. They specialize in RX7 stuff and I ordered the bearings for a 87-89 non-turbo diff. (I think it is the correct years). Fast delivery and know their stuff.
Keep us informed of how things go.

Everet <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/19/11 05:48 AM

Logansportage - thanks! That bit of info really takes a load off my mind. I'll be sure to post the details of the fit of the OBX diffs once I start turning bolts.

Everet - I have a dial indicator & magnetic base already. I don't have a 7-8" micrometer yet (for measuring the preload - based on this Miata Diff R&R). And I still have to pick up some basic tools (jack stands, jack, impact wrench, etc). I have the carrier bearings - got them from RockAuto for half the price at AutoZone. I'm just waiting for the circlips to arrive at the Mazda dealer later in the week. I was hoping to find a local mechanic to do the install. But it seems none are interested in doing the job unless they can bleed my wallet for $1500+. If you know someone in the Sacramento-area that will do the job for the fair-cost of labor, let me know.
Posted By: logansportage

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/20/11 07:31 PM

Just a thought, why not check to see if the Mazda dealer will set it up for you?

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/21/11 05:43 AM

I didn't give the idea of having a Kia or Mazda dealer do the install a second thought, simply because they usually only install OEM parts. And I've already starting buying tools to do the job. So I'm gearing up to do it myself. And following that line of thought, I have ordered the 7-8" micrometer from Enco. And I stumbled upon a heavy-duty floor jack while shopping at Costco today - 3.5 ton, steel frame, and all for $99. That's far better than what I was planning to pick up at Harbor Freight, and at a better price. Now I just need a slide hammer/puller, an impact wrench & some jack stands. Oh yeah... the circlips arrived at the Mazda dealer. So I will pick them up tomorrow afternoon... <img src="/forums/images/graemlins/kewl.gif" alt="" />
Posted By: Everet

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/21/11 12:37 PM

You can rent a slide hammer from autozone for free. They have a tool rental program.

Everet
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/21/11 10:23 PM

Everet - thanks for the tip on borrowing tools from AutoZone. That will definitely save a few $$$. On another note, I was calling around to get a price for having the bearings pressed on the new diffs, which seems to run about $15/bearing. That's much cheaper than buying a press at Harbor Freight... and spares my garage the additional clutter. One of the machine-guys gave me the name of a local shop that specializes in drive-train work. So I called to get an estimate for the install. Their pricing is much better - $100/end if I bring them the 3rd member to set up, and $300/end if they do the whole job. That's way better than the $1500 one of the local shops quoted. And the guy said they've done lots of Sportages over the years (dealer-warranty work)... and they are familiar with the OBX diffs (though they haven't installed them on a Sportage). So I'm seriously considering going that route - the 3rd member, at least...
Posted By: DennisThompson

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/22/11 02:27 AM

Looking at the front and rear diffs side by side the rear looks bigger, start measureing and they are in fact the same, I think the tone ring must make the rear look bigger.
When I installed my rear LS I didn't need a slide hammer, the axles slid right out after I removed the retaining bolts. I did not remove the pinion gear from the housing so all I did was measure the postion of the ring gear and make sure it went in the same. No special tools, just a sterit ruler. I did check the contact pattern and it checked out fine. It makes no noise and runs cool. I would start looking for another LS for the front but in a year or so I am planning on selling my Kia.

Dennis
Posted By: logansportage

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/22/11 10:51 PM

When I did my LS, I didn't need a slide hammer either. Just like Dennis, I undid the bolts and the axles slid right out. I also did not remove the pinion gear. I just pulled the diff out, then reset the gears to make sure the pattern was still good. To set the preload and back lash, I didn't have a dial indicator, but before pulling the diff out I checked with my hand to see what it felt like. I put it back just a little tighter than before and have had no problems with it other than using it enough now that it needs to be rebuilt. The Eaton design is a clutch design so it wares out. You use to be able to buy a rebuild kit, but it's no longer available.

Dennis,

If the front and rear are the same size, then I'm going to start looking for a 97 or newer that as the LS in the rear and maybe I can get a traction aid in the front. That or go with the OBX if it will fit in the front. The gear lockers would be the better way to go long term anyway.

Don't sell the KIA!!! Search and Rescue needs it.

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: DennisThompson

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/23/11 03:30 PM

I'm hopping my boy will buy it, he's in the S & R also.

Dennis
Posted By: logansportage

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/25/11 08:15 PM

The price is always right for a family member. <img src="/forums/images/graemlins/cheers.gif" alt="" />

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: 4runnernomore

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/27/11 10:59 AM

Quote

Dennis,

If the front and rear are the same size, then I'm going to start looking for a 97 or newer that as the LS in the rear and maybe I can get a traction aid in the front. That or go with the OBX if it will fit in the front. The gear lockers would be the better way to go long term anyway.

Don't sell the KIA!!! Search and Rescue needs it.

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />


Logansportage,

Have a look at this thread reference front traction (locker)

http://www.4x4wire.com/forums/showf...&an=0&page=0#Post1249137

Cheers, Chris
Posted By: 2002_Sporty

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/30/11 02:03 PM

Is this for real?
LSD
Or this
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/30/11 04:24 PM

I've seen the Eaton diffs for sale on a few websites. But I don't think all of them actually have the item in-stock. If you wanted to go that route, I would contact the company to verify they actually have the item, being that they seem scarce nowadays. There is a seller on eBay that has a current listing. But for a few bucks over the price of one of the Eaton clutch-type diffs, you could have two of the OBX diffs (assuming they prove off-road-worthy). I hope to have that question answered within the next week... or two... or three... <img src="/forums/images/graemlins/shiner.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 07/30/11 09:18 PM

I just realized that the seller on eBay is the same seller as the "Just Differentials" posted above. Looks like that seller has 3 in-stock at the moment...
Posted By: 2002_Sporty

Re: OBX Racing Differentials in a '97 Sporty?!? - 08/05/11 01:03 PM

Jeff Harvey jeff@justdifferentials.com
"Please review the attached estimate. Feel free to contact us if you have any questions. I have this unit in stock on my shelf at my location! smile Please let me know if you would like to pull the trigger on this unit. Please include your full shipping address. Thanks.

We look forward to working with you.

Sincerely,


Jeff Harvey
JT's Parts & Accessories
5980 Goodwin Rd
Cashmere, WA 98815
www.justdifferentials.com
Jeff@justdifferentials.com
509-888-AXLE (2953) ext. 111
866-399-7532 fax"

EAT19536 98-07 KIA SPORTAGE
10 BOLT EATON POSI 28 SPL
$599.00

But:
I want the Lock Right Locker for my rear.
So go ahead and get it if you need it.
Posted By: logansportage

Re: OBX Racing Differentials in a '97 Sporty?!? - 08/09/11 08:49 PM

I wonder if Jeff has the rebuild kit for the 98-02 Eaton diff. I already have this one in the rear of my Sportage, and would like a traction aid in the front. Either the OBX gear locker, or a 97 or older real LSD would be great.

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: hambodian

Re: OBX Racing Differentials in a '97 Sporty?!? - 08/10/11 12:08 AM

I had one of these OBX diffs when they first came out. It was on my turboed acura integra. It worked good. I took out the bolts and restacked the washers they had put in incorectly. Put the bolts back in with locktite and it was good to go. Another issue that may have been fixed by now was that the hole that the driveshaft went into was not chamfered on the inside. so it was easy to put shaft in but would not come back out without damage to the driveshaft. This was because the spring clips at the end off the shaft got caught on the non chamfered end. I may get these for my sportage front and rear. A lot off things to check before using it but it never broke once it was in. It's in my brothers car now. Just for reference I was pushing 30+ lbs of boost with a 1.8L 4cyl. on street tires. Not sure how much pressure that puts on the OBX.
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 08/10/11 06:13 AM

Still no update on the OBX diffs. But I did jack up the Sporty and figured out that the drivelines rotate counter-clockwise to drive the vehicle forward. Why is that important??? Because I need to make sure the helical gears are properly-oriented in the OBX diffs for both the front and rear axles so they will transfer torque during acceleration, as opposed to deceleration. I'll post the details on all of that, once I have it sorted out.

On another note, I did find the time to do a tune-up over the weekend - new Bosch Platinum+4 plugs, wires and coils, fuel filter, PCV valve, cleaned the throttle body... even installed a Spectre cone air filter (came with the vehicle, but had been removed to pass CA smog). My Sporty is running smoooooooooth!!! <img src="/forums/images/graemlins/smile.gif" alt="" />

And here's a pic of the "beast"...

[Linked Image]
Posted By: logansportage

Re: OBX Racing Differentials in a '97 Sporty?!? - 08/11/11 08:30 PM

Peabody, thanks for the update.

Not to hijack the post, but your signature says you have a 3" body lift. Your bumpers look like they have been relocated too. What did you do to get a 3" body lift and how did you relocate your bumpers?

Nice Sportage too!!!

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 08/12/11 03:12 AM

No worries about hijacking. The Sporty was lifted when I bought it. The seller had a set of 3" body blocks fabricated at a machine shop. For reasons not quite clear to me, he opted to get a 3.5" suspension lift from Everet, then lift the body 3". The suspension lift is perfect. The body blocks seem fine. But I don't know if they have recesses to keep them in place. I haven't noticed any signs of shifting. But some of the rubber pads seem to be a bit off-center. That noted, I haven't noticed any issues with the vehicle's handling that would be associated with the lift job. The only issue I have is that the body lift really threw off the geometry of the transfer case's shift lever. Now the lever has to slide under the lower-right corner of the tranny shifter to engage 4-low. In fact, I couldn't get it into 4L without trimming about 1/2" of threads off the TC lever. Now I need to fabricate a horizontal extension to offset the lever being under the console while in 4L. I almost had it fixed last weekend. But my extension was just a wee-bit too long, which prevents the TC lever from staying in 4H - it keeps popping back up towards 2H. Sooooooo close, yet so far away... <img src="/forums/images/graemlins/shiner.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 08/12/11 03:38 AM

Oh yeah - the bumpers have not been altered. Perhaps the low-angle of the photo makes them look off... or maybe the 3" body lift??? I'm dying to replace the factory-plastic with some kind of steel bumpers, to include a winch on the front. I've been looking at aftermarket bumpers for the Jeep Wranglers and Toyota pickups. I have yet to compare the dimensions and mounting points between them and the Sporty to see if either will work. I've also thought about fabricating my own. But I know they'll probably look like garbage. But if they do the job... <img src="/forums/images/graemlins/cheers.gif" alt="" />
Posted By: logansportage

Re: OBX Racing Differentials in a '97 Sporty?!? - 08/23/11 12:39 AM

A close up pic of the body lift block would be nice to see if you could post.

Also, they would have had to move the bumpers up or you would have a 3" gap between the top of your bumper and the body.

A picture of how your bumpers are mounted would also be nice.

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 08/23/11 04:24 AM

I spent a bit of time over the weekend beating on the front fenders and wheel wells so the beefy tires wouldn't rub (problem solved). I had to trim some of the front bumper off too, and noticed there were two metal tabs that have been added to connect the lower-portion of the bumper to the frame. I will take a picture of it and post it soon, along with the body lift.

As for the OBX diffs, I tore one of them down and took some photos, which I haven't been able to post yet because I tore down my computer for a home-renovation project. Once the PC is back together, the photos will be posted. I did find that the OBX diffs are the bare-minimum of manufacturing, though I can see how they can still be strong and hold up to the horses. There were lots of metal bits around the tapped holes and some rough-machined edges to boot. That doesn't surprise me though, because that correlates with others that have opened up the OBX diffs have found. If you want them to last, then a good cleanup of the rough spots and replacing the case bolts & belleville washers is pretty-much a must. Again, the pics will come soon. That concludes my report... <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 09/05/11 08:08 AM

OK, just posted pics of the stock bumper-mod and the front body-blocks on my winch bumper thread.

I have photos of an OBX diff disassembled. I want to add some comments to (in) the photos before I post them so they'll make more sense... or add to the confusion??? <img src="/forums/images/graemlins/zombie.gif" alt="" />
Posted By: logansportage

Re: OBX Racing Differentials in a '97 Sporty?!? - 09/07/11 11:46 PM

Thanks for the pics and info. I posted comments on that page.

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 09/18/11 07:54 AM

OK - Finally got the chance to sit down and prep the photos of the OBX diff. I've been holding off, in part, because one of the diffs was defective (cracks in the case) and I wanted to get it replaced under warranty. I just received the replacement diff on Thursday and its in good shape - inside and out. I have to say that I've learned my lesson on inspecting parts THOROUGHLY as soon as they arrive. The eBay seller only gives you 7 days to return parts. However, the seller exchanged the defective diff long after the deadline... after I explained that OBX was not responding to my emails and faxes. The exchange actually went smoothly. In hindsight, I think OBX and the 3 ebay sellers are either one in the same business... or very closely networked. But getting to the point, I figured it was wiser to wait to post pics after the exchange was done... just in case the sellers stumbled upon this thread (opening the diff voids the warranty, as does the installation in a non-approved vehicle ... what do you mean this ain't no Miata?!? <img src="/forums/images/graemlins/scared.gif" alt="" />).

Now for the pics...

Here's the diff, fresh out of the box...

[Linked Image]


Another view showing the ring gear mount...

[Linked Image]


Here's the case - opened up and gutted. The internal machining is crude and dirty - lots of metal shavings left from the tapping of the holes for the case bolts. But that can all be cleaned up...

[Linked Image]


Here's a layout of the internal components...

[Linked Image]


Belleville washer comparison - The Chinese washers are known to be of poor-quality and should be replaced, along with the case bolts. I bought 2 kits of washers & bolts, as noted earlier, to replace the Chinese parts. You can see in the photo that the stock washers are ugly. But they also lack "spring" and have failed in some diffs (don't forget that this diff is only $279 U.S. - a little elbow-grease, some bolts & washers, and this diff might roll a tank!)...

[Linked Image]


Sun gears showing circlip grooves...

[Linked Image]


These are the components that form the "spring assembly". Its basically the belleville washers stacked between two splined-retainers, which sit in an internally-splined housing. The outside of the housing is grooved to receive the helical satellite-gears...

[Linked Image]


This is the spring assembly in its assembled-state. Note the height created by the washers - compressing the stack creates preload on the sun gears...

[Linked Image]


Here's a photo describing the proper-orientation of the sun gears. This is critical for proper-functioning of the differential...

[Linked Image]


This is the "don't do it like this" orientation...

[Linked Image]


Here's my "trying to make sense of it all" diagram. This shows the relationship of the internal components as they would interact within the case. Basically, the pinion turns the ring gear and case to provide forward-travel. The helical-planetary gears are, in turn, rotated by the case - turning in the opposite direction of travel. The planetary gears subsequently-turn the helical-sun gears in the forward-direction, which are splined with the axles...

[img]http://i999.photobucket.com/albums/af117/peabody1986/Sportage/OBX%20Diff%20Project/OBXDIFF11-1.gif[/img]


(NOTE: I had to edit the photo and the description below... got my thrust directions reversed... what you see now is correct... I think <img src="/forums/images/graemlins/baby.gif" alt="" />)

I still don't understand how this design provides limited-slip, or torque-distribution (it might not really slip... not much, at least). What I do understand is that the planetary gears thrust laterally and internally against the diff case (away from the wheels) when under the load of forward-travel. That's why the orientation of the sun gears is critical: you want the sun gears to thrust away from the belleville washers. Get it wrong and you grind up your washers while you drive because the axles/sun gears continuously-compress the washers. Now here's where I get lost... when the torque-bias reaches the threshold-ratio (not sure what it is for the OBX, or if it is even a static value), the planetary gears on the side with less-torque get pulled outward - away from the center, pulling the low-torque sun gear towards the belleville washers (I think)... while the high-torque side retains the normal-positioning. And somehow during that action, the torque is distributed to the wheel with better traction. As long as there is some torque on the low-traction side, you will get some percentage of torque delivered to the traction-wheel. However if the low-traction side spins freely (i.e. is in the air), then no torque is delivered to the traction-wheel (zero torque X a bias ratio is zero - or zero torque delivered to the wheel on the ground). The simple fix for that is to lightly-touch the brake while driving - the drag of the brake returns some torque to the low-traction wheel, and X-times more torque to the drive-wheel. I just don't understand how the gears slip or slide to transfer torque unequally... there's not much room in the case for them to move much more that a millimeter, or maybe a few. <img src="/forums/images/graemlins/confused.gif" alt="" />

Jump in if you can explain... <img src="/forums/images/graemlins/shiner.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 09/18/11 09:23 PM

Well, you think that you understand something and then you come to find you're wrong again...

I found a video on YouTube that shows how the Eaton TruTrac differential functions to distribute torque. It is another helical-gear design, but only uses 3 helical-planetary gears per side (they call them "pinions"). The essence of the design is the same as Quaife, OBX and the Type-2 Torsen. And it all comes down to this - The planetary gears don't rotate when the torque bias is equal between the two sides (50%:50%). Once the ratio changes, the planetary gears begin to rotate. And though the planetary gears for both axles mesh in the center of the differential (common to all designs mentioned), they somehow allow the axles to rotate at different rates... which appears to be all based on torque and the pitch of the helix (changing the pitch apparently changes the torque-bias ratio [TBR]). So it might not really involve "slip" - at least not in the same sense as you find in a clutch-based diff.

Also, I don't think the spring-effect of the belleville washers is critical to the function of torque-distribution. After doing a bit more research, I came across some posts that claim the first Quaife diffs didn't have the spring-stack. They were added to eliminate the annoying sounds caused by the sun gears rattling in the case during turns. Again, it is important to orient the sun gears so they thrust away from the spring assembly "naturally", when under the load created by forward travel.

Here's a link to the clip on YouTube... The demonstration of the torque-split starts around 1:20 min in the video.

Eaton TruTrac video


Here's another clip that shows how the T1 torsen works...

T1 Torsen clip


Oh, you can't leave out the Lego model of the T1 Torsen...

Lego Model of T1 Torsen...


And here's a link to another clip that shows how the TruTrac distributes torque - the Land Rover shown has the TruTracs installed in the front and rear. The "touch the brake" technique is shown at the very end...

Land Rover with TruTracs demo
Posted By: Everet

Re: OBX Racing Differentials in a '97 Sporty?!? - 09/19/11 12:23 AM

GREAT PICS AND EXPLANATION. When are you going to install them?

Everet <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 09/19/11 12:36 AM

Ummm... not until after I get the bumpers installed. I'm mid-way through with that project - have no license plates on the Sporty and have gone too far to put the stock bumpers back on. That said, I might just pay the shop in Sacramento (http://www.jawsgear.com/) to do the job, simply because I have too much stuff piled up on my plate and I'm itchin' to get out an play... <img src="/forums/images/graemlins/evil.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 09/20/11 05:48 AM

I was looking for more videos that demonstrate how torsens work. I found another from the guy with the Land Rover equipped with TruTracs - front and rear. This one has some good footage of some 4-wheel driving in the snow. I have to say that I'm pretty impressed by the traction he's able to get with helical diffs. I hope the OBX diffs can do the same...

Here's the link: http://www.youtube.com/watch?v=T8kYCqzYWyg <img src="/forums/images/graemlins/kewl.gif" alt="" />
Posted By: logansportage

Re: OBX Racing Differentials in a '97 Sporty?!? - 09/22/11 06:11 PM

Peabody,

AWESOME write up!!! Very Well Done!!! I did a similar one for the Eaton LSD, but never posted it.

You are really making me consider doing the same thing to my Sportage.

My rear LSD is in need of servicing, and maybe I'll just replace it with the OBX unit.

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: 2002_Sporty

Re: OBX Racing Differentials in a '97 Sporty?!? - 09/23/11 11:14 AM

Peabody,
Would you please tell me where you got your OBX differential.
I read that it was from e-bay. But I do not know what vehicle and year you typed in to find the correct diff. Please tell me here. I am mechanically declined.
I wouldn't mind one for the front diff on my 2002 Sporty.
Posted By: TheGoat

Re: OBX Racing Differentials in a '97 Sporty?!? - 09/23/11 01:22 PM

as far as what i understand, 94+ mazda miata.

since you have an 02, you'd need an RX7 diff for the rear, but just the front would be 94+miata.
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 09/23/11 04:34 PM

I just checked eBay - 2 of the 3 sellers have the diffs listed
( eBay search results here ). I bought mine from TuningDepot. They were good about replacing the defective diff long after the 7-day return period, once I had emailed them photos of the cracks. If you get one, inspect it closely inside and out as soon as you get it. Don't be like me... <img src="/forums/images/graemlins/zombie.gif" alt="" />

I'm pretty sure (95%) the OBX diff will work in the front-end of your Sporty because, if I recall correctly, Kia only changed the rear diff's design in the 98-02 models - no changes to the front diff. Again, I'll let the world know how my experiment turns out once I finally get the parts installed. <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/scared.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" />
Posted By: logansportage

Re: OBX Racing Differentials in a '97 Sporty?!? - 09/23/11 11:26 PM

My understanding is this:

If you have a 97 or older Sportage you can use the same diff front or rear, so you could use the OBX lockers with no problems.

If you have a 98 or newer Sportage you cannot use the same diff front or rear. The reason is in 98 KIA changed the rear axle spline count from 26 spline to 28 spline.

However, if you change out the axel shafts for 97 or newer axel shafts you can use the OXB locker. All other parts are exactly the same.

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: 4runnernomore

Re: OBX Racing Differentials in a '97 Sporty?!? - 09/28/11 02:05 PM

Quote
My understanding is this:

If you have a 97 or older Sportage you can use the same diff front or rear, so you could use the OBX lockers with no problems.

If you have a 98 or newer Sportage you cannot use the same diff front or rear. The reason is in 98 KIA changed the rear axle spline count from 26 spline to 28 spline.

However, if you change out the axel shafts for 97 or newer axel shafts you can use the OXB locker. All other parts are exactly the same.

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />


Can anyone confirm this. That a 97 or older sportage has the same differential centre front and rear?

Cheers, Chris
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 09/28/11 11:04 PM

I'm 99.9% sure. The install of the OBX diffs in both axles will prove or disprove the theory absolutely... <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: logansportage

Re: OBX Racing Differentials in a '97 Sporty?!? - 10/03/11 11:59 PM

When you search for the rear Eaton LSD there are different part numbers for the 95 - 97 and 98 - 02.

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 10/04/11 05:08 AM

Yes, there are different part numbers for the Eaton-Sporty LSDs.

93-97: #19519
98-09: #19536

Eaton LSDs for Sporty's on eBay

Hope that helps... <img src="/forums/images/graemlins/kewl.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 12/04/11 10:29 PM

"Houston, we have a problem"... on the rear diff, at least. <img src="/forums/images/graemlins/zombie.gif" alt="" /> <img src="/forums/images/graemlins/zombie.gif" alt="" /> <img src="/forums/images/graemlins/zombie.gif" alt="" />


I went to a bone-yard yesterday to pick up a spare rear diff (26 spline), just so I could pull it apart to confirm or deny that the OBX diff spec'd for the Miata will fit. It won't. It turns out that, in the U.S. at least, the 26 spline rear diff with 7.5" ring gear IS DIFFERENT than the front diff with 7" ring gear. I haven't yet compared the front and rear diffs directly. But I did test the fit of the 7.5" ring gear and ABS ring (tone ring) against my OBX diffs (had to check both to convince myself that the results were true). They are - the 7.5" ring gear is larger than the mount and case on the OBX diff. <img src="/forums/images/graemlins/zombie.gif" alt="" /> <img src="/forums/images/graemlins/zombie.gif" alt="" /> <img src="/forums/images/graemlins/zombie.gif" alt="" />

I don't understand how anyone got the rear LSD of any Mazda RX-7/Miata diff to fit in the rear axle, unless they set it up with front ring gear and pinion. Is that even possible to do and still keep the proper gear ratio between front and rear axles??? <img src="/forums/images/graemlins/confused.gif" alt="" /><img src="/forums/images/graemlins/confused.gif" alt="" /><img src="/forums/images/graemlins/confused.gif" alt="" />

Here's a few photos to show you what I have found...


The OBX diff set on the 7.5" ring gear from the 26 spline diff...

[Linked Image]



A view of the offset hole pattern when one side is lined up... <img src="/forums/images/graemlins/scared.gif" alt="" />

[Linked Image]



ABS "tone" ring should be snug on the ring gear mount... not even close.

[Linked Image]



Ring gear set on the OBX case. It should be snug on the case-body... again, not even close. <img src="/forums/images/graemlins/scared.gif" alt="" /> <img src="/forums/images/graemlins/scared.gif" alt="" /> <img src="/forums/images/graemlins/scared.gif" alt="" />

[Linked Image]



So it looks like I'm "S.O.L." on getting the OBX diff in the rear. I could look into having the ring gear drilled for the smaller bolt-pattern and having spacers made to adapt the case for the ring gear and the ABS ring. But that will be a lot of $$$, if it would even work. So I'm going to look into other options for the rear axle. I'll let you know what I find, if I find anything. And I will let you know what comes of the front diff once I get into it... <img src="/forums/images/graemlins/confused.gif" alt="" /> <img src="/forums/images/graemlins/scared.gif" alt="" /> <img src="/forums/images/graemlins/zombie.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 12/07/11 07:07 AM

"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="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 12/08/11 05:16 AM

Plan "A" is a no-go. The Ford splines are too big, as I suspected, but refused to believe until I could test the compatibility myself. Still working on the other options... <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 12/09/11 10:50 PM

Well, the local 4x4 shop can't find an Eaton LSD. So getting one through them won't happen. On another note, I have a CAD program and made a drawing of a "hybrid" OBX case (ring gear side only) with the Kia-specs for the ring gear mount. Here's a comparison of the stock OBX case for the Miata and my red-headed-step-design. Sadly, I've been calling around to local machine shops all morning to get a quote, but can't find a shop that will even look at the job because:

A) "We don't do small-volume"

or

B) "We won't make automotive parts"

<img src="/forums/images/graemlins/angry.gif" alt="" />


So, if anyone knows of a machinist that can/will do the job for a fair price, let me know. And now for the pics (3D renderings)...


OBX stock casing...

[Linked Image]


The "hybrid" case with Kia's 7.5" ring gear mount...

[Linked Image]


<img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 12/10/11 09:02 PM

Because I was unable to find a local machinist to bid on my job, I took my design to some on-line prototyping/machining companies. One is based in the U.S. The other is in Hong Kong with manufacturing done in China. The U.S. company responded with a bid exceeding $1200.00!!! <img src="/forums/images/graemlins/zombie.gif" alt="" /> <img src="/forums/images/graemlins/zombie.gif" alt="" /> <img src="/forums/images/graemlins/zombie.gif" alt="" /> I'm still waiting to get a bid from the Chinese-based firm (which I suspect will be much lower). On a side-note, I have to say that, given the state of the U.S. economy, I would expect more companies would be willing to bid, and that the bids would be reasonable. Now I understand why our job-market and manufacturing-base is shrinking... <img src="/forums/images/graemlins/rolleyes.gif" alt="" />

On related note, I decided to contact OBX Racing to see if they would be interested in machining a prototype. If it works, they will instantly have a new product line to fit the pre-'98 Sportage rear diff. And if they simply swap the axle gears with 28-spline x 29 mm (which is the same size as the splines on Honda's S2000, which they already sell LSDs for), then they will have products that cover all Sportages manufactured through 2005. Ah, but with my luck, they won't want to do it... <img src="/forums/images/graemlins/shiner.gif" alt="" />

<img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 12/18/11 03:59 AM

I have finally started work on the front diff. I have put the rear diff on the back-burner until I can find the "least expensive option" that is suitable for regular off-road use. As noted, that may involve having a the ring gear-side of the OBX case fabricated with the 7.5" ring gear mount. Or I will go with a Track Finder locker, if I can get one. Either way, the rear diff won't be done anytime soon.

As for the front, I have the diff assembly ready to pull. That is a lot more involved than it sounds - You have to pull the wheels, brake pads and rotors, unbolt the bottom joint on the knuckles (popping out the outer tie rods helps too), swing the knuckle to slide out the CV half-shaft, then pull the shafts out of the axle housing. However, the knuckle (a.k.a "spindle") seals were shot on both wheels, leaving the needle bearings (spindle bearings) corroding in petrified, water-contaminated grease and rust. The passenger side was the worse-off of the two. I didn't even realize it was a bearing until I noticed the black "rocks" I was pulling out of the muck used to be needle bearings. <img src="/forums/images/graemlins/zombie.gif" alt="" /> And that lead to a panicked-frenzy to find bearings and seals. They arrived today, along with 2 new outer tie rod ends (rubber boots were torn into 2 pieces). I have some photos of the project and will post them soon.

Anyhoo, I was holding off on installing the OBX diff until I was sure I could install the new side bearings. That worked out like a champ using my "poor man's bearing press"... a 3/8" bolt long enough to reach through the OBX case halves (separated into 2 separate pieces) and some steel washers & a plate. I simply lubed the bearing mounts with some grease and wrenched the bearings down (keeping a watchful eye to make sure they went on straight) - it worked great! I'll post some photos of that bit too when I have a chance.

So as it stands, I have the bearings on the OBX diff, the diff housing ready to drop, new parts to install (after I clean out the rust & crud a little better), and the OBX diff to reassemble and swap out with the stock carrier. I hope to get that all done tomorrow. I'll post the results after... <img src="/forums/images/graemlins/shiner.gif" alt="" />

<img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 12/19/11 06:53 AM

The OBX diff fits in the front-end & I have the diff housing back in the Sporty with the half-shafts installed. But that's as far as I've gotten. I had a battle with the backlash and preload when assembling the diff. And I think much of that was caused by the magnetic base on my dial indicator being just a wee-bit unsteady. In hindsight, I should have used a long bolt with short threads as a base for the indicator, and just bolted it through one of the pumpkin's mounting holes. I also found that my "bearing press" didn't seat the bearings completely. But I also found that using a section of 1.5" PVC or ABS pipe worked perfectly for finishing that job - just tapped them down with the pipe and a rubber mallet. <img src="/forums/images/graemlins/kewl.gif" alt="" /> If I would have used a thin ring of 1.5" pipe with the "press", the bearings would have seated perfect on the first go... I still have to get the knuckles and hubs together, oil in the diff, and finish up the front brakes. But I think that should all go smoother, now that I've found all of the bum parts and have the replacements in hand... right?!? <img src="/forums/images/graemlins/scared.gif" alt="" /> Pics will come soon...


<img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 12/23/11 06:59 PM

Update: I was able to get everything back together, despite a nasty bout with the flu (still recovering), to include replacing the front brakes and lengthening the front brake lines (plenty of line when the wheels hang). I road tested the front diff with the hubs locked in 2wd - no strange sounds or pulling. Then I did some short laps around the neighborhood in 4wd and everything felt fine. I'm now in So Cal and hope to do some testing on the dirt. <img src="/forums/images/graemlins/kewl.gif" alt="" /> I will let you know how it goes...

As it stands, the OBX diff works in the sporty's front end. And for the price and a little elbow grease, it may be a good option for getting a torsen-type LSD for the front axle. Again, I will let you know how it performs...

<img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 12/28/11 01:56 AM

I'm back from So Cal. Unfortunately, my battle with the flu was far from over. It was merely shifting gears. And that kept me from getting out and testing the OBX diff in the front axle. However, the vehicle is handling better now and the new brakes are great!

Here are some photos of my "poor man's bearing press"...

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Now for the spindle/knuckle bearings - here are a few pics of what I found on the passenger-side knuckle...


My CV half-shaft covered in greasy rust (mostly rust). But the splines were fine...

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The backside of the knuckle with the seal still in place...

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And a close-up of the crud and bearing... <img src="/forums/images/graemlins/zombie.gif" alt="" />

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It took me a few minutes to realize these bits were the needle bearings...

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Hey, isn't this thread about the OBX diff?!? Yep. And here are a few pics of the assembled diff... <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" />

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<img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: kia74

Re: OBX Racing Differentials in a '97 Sporty?!? - 02/09/12 10:55 AM

So what is happening did it work or not <img src="/forums/images/graemlins/confused.gif" alt="" />.I am gettin itchy <img src="/forums/images/graemlins/sleeping.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 02/10/12 03:50 AM

Yes, the OBX diff works in the front axle of the Sportage. And that should hold true for all 4x4 Sportages made from 1995-2005 (they all have 26-sline x 27mm axles and 7" ring gears and use the same carrier and pinion bearings - only the rear diff changed starting in 1998, which was only a change in the axle and spider gears' spline count to 28-spline x 29mm; nothing else). As far as testing, I have only road tested it on paved streets. I haven't had a chance to hit a trail yet. However, it feels fine - no clunks or chunks or grinds. I am confident that it will be an improvement over the open-carrier that is stock equipment on the front end. For the price, it seems to be a very good solution... so far. <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 06/12/12 01:47 AM

Update... I'm having an issue with the front drive. I'm getting a popping noise when I turn left in 4wd, which I can feel through the steering wheel. <img src="/forums/images/graemlins/scared.gif" alt="" /> I think everything is good with the front diff. But the front drive wasn't engaged. Unknown to me at the time, my Sporty will only engage the front drive when I shift into 4wd (high or low) with the tranny in neutral. "Shift on the go" or even stopped in "drive" doesn't do it. Going straight or turning to the right with the transfer case engaged works fine. I can feel the front tires gripping. So I know the OBX diff is working. But I'm going to have to do some investigating to figure out what's going on. More to come, once I have a chance to to dig into it... <img src="/forums/images/graemlins/baby.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 10/22/12 06:31 AM

Finally... I have an update!!! I was able to pull my front axle and tear down the OBX diff. I found the cause of my trouble - the reason why the diff was catching and banging when I tried to turn left with the 4x4 engaged. The sloppy machining tolerances allowed one set of the helical gears (planetary) to contact the opposing axle gear ("sun" gear) when the vehicle was turning to the left. Straight was fine, as no gears move within the casing. And the right turn was fine because the gears didn't touch (barely...). Here's a pic of the gears that were catching, chipped teeth and all. <img src="/forums/images/graemlins/zombie.gif" alt="" />


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It took a bit of thought, but I was able to come up with a fix: I took the gears to the bench grinder and beveled them so they can overlap without catching teeth. I tested the mod thoroughly to ensure the problem was solved. I did this by assembling the casing with all parts except the belleville washers, inserting a spline shaft in one of the sun gears and spinning the gears while holding the shaft upright with the diff on top (like a head on a pike... <img src="/forums/images/graemlins/evil.gif" alt="" />). The weight of the diff will push the sun gear up while the weight of the opposing planetary gears will pull them down. The lack of the spring washers allowed the "system" to act as if it were under sufficient load to overcome the preload of the washers, which is exactly what happens when the wheels turn at different speeds. If both gear-sets turn freely without hangups (have to test both sides this way), then the problem is gone. <img src="/forums/images/graemlins/kewl.gif" alt="" /> Here's some pics of the modded gears...

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And here's a pic of how the gears load into the case - the heavily-beveled ends all face toward the center, because that's where the overlap occurs...

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Once I had it all sorted out, I reassembled the case and proceeded to install my new 5.38 R&P set (those details in another thread). Here's a tip for anyone that may decide to give the OBX diff a try - It's easier to torque the case bolts if you mount the diff in a vise like this (I torqued mine to 40 ft-lbs using red thread locker)...


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Another issue I ran into while setting up the R&P was that the ring gear mount was out of "true" by about 0.004". That doesn't sound like much. But when the ring gear wobbles towards and away from the pinion, it can and will throw your backlash off. I found the simple way to fix it was to file the centerline-face of the diff case (ring gear side) to eliminate the high spot (the area that measures farther away from center). It took a few hours of filing (I used a diamond hone for sharpening blades), assembling the casing (no gears... no need) and loading the diff into the housing for measuring. But it worked! <img src="/forums/images/graemlins/cheers.gif" alt="" />

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Once that was sorted out, I did the final assembly on the diff and finished up the 5.38 R&P upgrade of my front axle (those details in another thread)...

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I still have to put my fix-it-mods to the test. But I can't do that until I finish installing the 5.38 R&P set in my rear axle. I hope to get that done next weekend, time permitting. I am pretty sure the problem has been solved and the diff will function normally. That said, I want to table a few "insights". First, the direction of the sun gears may not make a difference after all. I say this because, after sorting out the issue with overlapping gears, I came to realize the following...

1) No gears turn when the wheels turn at the same speed (this isn't new and has been noted earlier in this thread).

2) Because the gears are not moving under the conditions of point (1), the pulling inward or pushing outward of the planetary gears against the case is a non-issue. It doesn't matter. (That's an epiphany)

3) When turning, one set of planetary gears will pull towards the center while the corresponding/meshed sun gear will move away from center. The opposing gear set will perform oppositely: the planetary gears will move away from center while the corresponding sun gear will move towards center. When you turn left, one set of gears shift to center. When you turn right, the other set of gears shift to center. This is a big epiphany!!! (For me, at least).

Thus, the direction of the sun gears, as mentioned earlier in this thread based on references from other OBX discussions on other forums, doesn't matter. This is due to the fact that the shifting of gears towards and away from center is dependent on variation in wheel speed (i.e. one wheel rolling faster than the other). And each gear set will move towards or away from center only when the wheel speed varies specifically (like turning right or left). The critical point of this is that the gear sets on one side turn in the opposite direction of the other side when wheel speed differs. And if the planetary gears from one side overlap the sun gear on the other side, the teeth of both will catch - catastrophically. This will happen because the planetary gears from one side and the sun gear from the other side BOTH MOVE TOWARDS THE CENTER under one specific turn condition (left or right). That's why bad things happen if the machining tolerances are crap... And that's what happened to me. Fortunately, the fix was relatively simple.

Taking all things into account, I am hesitant to recommend the OBX diff - assuming it works well off road. I say this because the quality of the product is low. It's a made-on-the-cheap-in-China product. The machining tolerances are sloppy and I had issues with the quality of the casting (case had pits, pockets and cracks). I was able to fix the issues (cracked case had to be exchanged - not an easy process). And the fixes, as I've noted, weren't too difficult, just tedious. For $279, a little elbow grease will give you a tough little diff. But the OBX diff is now selling for $358-$378 on eBay. That's another $100 over what I paid. And for that price, I'd shop for a quality-made diff that will drop in without hassle, even if it was a clutch-type LSD (or a Track Finder locker for the front). I will report back when I have had a chance to test the mods on the OBX diff, and assuming they work, how the OBX performs on the trail. Wish me luck...


<img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 10/22/12 10:01 PM

One more issue with the OBX diff that I forgot to note in my previous post... The shoulder of the ring gear mount on the OBX casing, where the ring gear should have a press-fit, was 0.002" smaller than the inside diameter of the ring gear. I tried mounting the gear to see if the ring gear bolts would self-center the ring gear. But it didn't happen. I then began to think of ways I could shim the ring gear against the case so it would center properly. I decided to work with a section of 20-gauge steel wire (solid) because I had it on-hand. Basically, I took a length of wire just shorter than the circumference of the diff case at the ring gear flange/mount and wrapped it around the base. Then I set the ring gear over it and tucked the wire into the chamfered edge of ring gear, which meets the corner of the flange and case. This bit of wire filled the gap between the corner and the flange. And when I bolted the ring gear down, the wire acted like a shim that was a crush-fit. It worked pretty well, bringing the measured runout down to 0.001". It isn't ideal. But it worked. And that bit of wire will not slip out of place - no way for it to move at all... <img src="/forums/images/graemlins/kewl.gif" alt="" />

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Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 10/29/12 05:55 AM

Update - I was able to finish installing the rear diff with 5.38 R&P. After giving the rear diff a run of testing, I found a gravel lot where I could test everything in 4wd. It works! So it appears the OBX diff is actually working without catching gears - no bad noises when turning hard in any direction!!! It actually seems smooth. And I did jump back and forth between 2wd and 4wd to make sure the front axle was actually engaging... <img src="/forums/images/graemlins/shiner.gif" alt="" /> So far, so good. I will post more after I have a chance to hit a trail...

<img src="/forums/images/graemlins/kewl.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" />

<img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Peabody

Re: OBX Racing Differentials in a '97 Sporty?!? - 10/30/12 04:27 AM

I took my Sporty back out for a bit of break-in driving. Richmond Gear recommends driving for 30 minutes at "normal driving speed", then letting the vehicle rest to let the gear oil cool down. This process is to be repeated for a total of 3 break-in runs. So I took the rig back to the gravel lot and gave it another go. I was able to turn hard left and right without issues. And the front wheels seem to be getting some good grip, though the Track Finder locker in the rear will overcome the steering a bit if I goose it a little too hard... <img src="/forums/images/graemlins/notooth.gif" alt="" /> That said, the OBX diff is working well and without any odd noises - it's running smooth. Now that I've tested it on a gravel lot, I have the utmost confidence that it will work well enough to get me out of the McDonald's drive-thru, should I ever have the need to crawl my way out. <img src="/forums/images/graemlins/lol.gif" alt="" />
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