Well I took the plunge and finally ordered the OBX helical LSD that keeps getting tossed around on this forum. I'm pretty sure my "Torsen" rear end that my mechanic from years ago sold/installed for me is an open diff. I did the parking lot test and it failed miserably. Once I get it I'll replace the bolts with something stronger (as I've read this is a failing point on Honda versions of the OBX LSD). I'll post pics once I get it and feedback when it's installed.


******************Update - 04/29/2011
The OBX Diff is installed and functioning perfectly. Here's a quick how to:

1. Buy the OBX Helical Differential
2. Order the bolt and washer kit from here:
http://rbryant.freeshell.org/obx_washers.htm
3. Open up your new OBX differential.

4. For some reason OBX appears to sometimes assemble rear wheel drive differentials in a FWD configuration. Here is the wrong and right way:

5. If your gears look like the WRONG picture, you need to swap the gears on the top with the gears on the bottom. This is easy to do.
Mine when I first opened it

And with the gears swapped (top to bottom)

6. If your gears are in correct orientation, then just remove the top gears and remove the stock OBX washers. The configuration that worked well for me was all new 6 washers in this orientation: )()()(
7. Reassemble, put blue thread locker on the new bolts, and install in a diagonal pattern. Torque to 28 ft/lbs.
8. To install into your 1.8 diff you will need two new bearings, and a couple of seals. Direct from Mazda cost me $200.
9. BEFORE YOU INSTALL - you might want to take your shiny new differential to a machine shop and get them to measure the tolerance on the surface that the differential ring mounts on. Mine was not machined properly from the factory and was out 0.007, which caused the ring to pop out of the pinion. $100 of machining later and it was perfect.
10. Use the same gear oil that you use in the regular miata diff. I put in Royal Purple Max Gear.
11. Enjoy your new diff.

Cost breakdown:
Differential: $250
Bearings & Seals: $200
Bolt kit: $15
Gear oil: $20

That sits at about $485. If you need to machine the unit true then your cost might vary, but mine was $100 which is probably on the higher end of the price. If you consider that if you install a used Torsen or any other diff you will still need the new bearings and seals, then this actually turns out to be quite a sweet deal.

* One misconception to note. This is not a direct copy of the Quaife differential. It actually appears that OBX used some sort of in-house design, and it is unique.

 

I would inspect the conical pre-load washers, a lot of the Honda guys replace these right away. They also found the backside of the side gear splines aren't tapered so it's extremely hard to get the stub shaft or axle out.

 

Interesting, never heard of them making a diff. At $290 it's actually something I can afford. Although googling "OBX LSD" comes up with the first link of a "buyer beware" thread from a Honda forum, something about an axle not coming out a week after installation. If that's the worst part of the unit, it's not too bad. They damaged transmissions while attempting removal, something we don't have to worry about.

I'd just be concerned with it actually performing as an LSD.

 

Given that I'm considering buying one in the near future, I am curious about how it is. Will be watching this thread closely...

 

A friend of mine is a fabricator for Morris Tuning in new york. They do ridiculous Honda builds, and for people on a budget they have used the OBX lsd's before with success. I'm hoping the same goes here.

 

I don't see how my Torsen can possibly last much longer.

 

http://rbryant.freeshell.org/obx_washers.htm

 

From what I understand about them, they're basically a copy of a Quaife.

 

A copy of a Quaife with shitty washers then? Doesn't sound too bad if new washers and bolts are $32 shipped.

I think I'll have to try this when I feel the urge to spend $280.

It's quite possible these are a copy of the Quaife, albeit with sub standard quality control. I worked as a machinist for three years, specializing in gear cutting. So all this information is common knowledge to me. It's interesting that he said honing with a brake cylinder hone helped, as most good splines are a major diameter fit. Aka the diameter centers the two pieces, where as the spline only locks it in. The bevels are merely a by product of not checking your parts enough. Anyone here know how to properly measure a bevel on a shaft? It's not a very precise measurement.

 

Where did you buy this and do they come in 1.6 diff size?

 

Ebay.

No. Sorry dude :(.

 

it would be nice if someone like emelio or sav looked into these. buy them, overhaul as necessary to make it reliable, then upcharge a little to resell

 

in for results!

 

So can this withstand more torque and abuse than a torsen?

 

I've seen a side by side teardown of a quaife & obx LSD, they are the same design but the fit and finish on the quaife was considerably better. I'm going to give the obx a shot regardless.

 

I have no experience with these, but I have seen numberous Honda builds with 500+whp using these. If you use that rebuild kit it should be great.

 

Thanks for that link. I just ordered the bolt/washer kit.

 

Nice one. Does it fit straight in the 1.8 diff?
Please do a report on the installation!

 

It should fit straight into the 1.8 diff, and I'm on the fence whether to do it myself or just get a transmission shop to swap it out. I'm busy with a bunch of garbage and I'm lazy.

 

I actually have one in my c60 (6spd) that is swapped into my corolla. works just fine. I did replace the bolts and Belleville springs before install with the ones from the posted link. I arranged the springs for max preload, a pattern like this ()()(). also torque the new bolts down to 40ft-lbs in a star pattern, kinda obvious.

It has gotten it's fair share of abuse since its install. I have no complaints