Talked to a guy at Randy's ring and pinion today to order a set of 3.42's and a rebuild kit for the factory posi because I don't want to spend $500 on a beefy aftermarket posi for a 7.5. The guy asked what kind of posi came in the car. I don't know what to tell him. So what kind of posi comes in a 1987 Iroc Z with a 2 series carrier with 2.73 gears??? Has anyone ever rebuilt their factory posi in a 10 bolt that could provide some advice and confirm if its even possible??? Anybody know of anywhere else to get the rebuild kit??

It's an Auburn.

In theory, it's possible; but Auburn long since quit supplying ANY parts for those. You might be able to find some laying around somewhere in GM's parts system; but I seriously doubt it. I tried to get parts to repair about a 1997 one, in 2003 or 4; called Auburn direct, finally, when I couldn't find anything; they even had already discontinued those.

Does Auburn support their aftermarket ones any better?

Their most recent aftermarket ones, they have some kind of a program for; but it has to be pretty new to be eligible. Doesn't apply to the old stock ones though. www.auburngear.com/aftermarket

That's cool. $115 for an exchange, assuming mine is new enough to qualify.

Right:

I actually went and looked at it and read the fine print.

http://www.auburngear.com/aftermarke...EX_Program.pdf

The unit itself has to have a production date less than 4 years old, or you have to have proof of purchase less than 4 years earlier.

4 years isn't of much value, to a part that is supposed to last for decades.

I will NEVER buy an Auburn product again, after the bad experiences I've had with them.

I bought it used, so it is probably too old. Works well so far. Out of curiosity, when you had problems - did it just quit working correctly, or did it destroy other parts when it failed?

Key point to note:
you bought 3.42 gears to replace your existing 2.73 gears, and you want to rebuild (or reuse) your existing posi right?
You know how the 2/3 series thing works right?

If you're asking about mine, what it did was, the small end piece on the pass side that the bearing presses onto, came loose in the carrier; so the whole big piece, the main outer piece with the ring gear on it, could sort of flop around in the housing. Had a nasty vibe. Ruined a gear set. When I called them they basically told me I was SOL. I had bought it used, and it was maybe 7 years old at the time; so NOT ONLY was it ineligible for the "program", BUT ALSO they didn't have any parts for it any more and hadn't for several years. Basically, ZERO effort to stand behind their product. I bought an Eaton to replace it. Auburn can go pound sand for all I care, I'm not going back.

My Auburn was working great too, then one big bang later it was dead.

I would second the Eaton.

Yeah, a "replacement program". What a joke! By the time you actually read all the fine print to that deal like Sofa did, it basically amounts to a pile of beans. Besides that, the program is really just a band-aid to supplement an inferior product design. Even Auburn units usually last longer than 4 years, so the replacement deal means nothing. At least if the clutches ever burn out in your Eaton unit, even if it's 20 years from now, you can buy the parts to rebuild it. Another thing to note is the picture that mcgee posted. Eaton's housings are made from high strength steel, and the spider gears are forged. A buddy of mine grenaded his factory Auburn unit exactly the same way as the picture above with a stock tpi motor.

Yeah, 3.08 and higher (numerically lower) is 2 series and a 3.23 or lower (numerically higher) is a 3 series. Randy's Ring and Pinion sells thicker ring gears to compensate for the 2 series carrier. That way you don't have to run a spacer or change carriers.

I was just wanting to know if it could be rebuilt because I get sick of the weak springs in this posi. Is there a way to space the springs to make them clamp harder??? Turning to the right and nailing it...1 wheel peel. Turning to the left and nailing it...all over the road with 2 spinning. Nailing it from a stop going straight...its questionable, sometimes 1, but mostly 2.

Did any of the factory 7.5's come with an Eaton posi unit that isn't a Govlock???

In theory, yes; in practice, no. There's no parts to do it with.No.

What if I were to just put gear lube only in the rear end with no additive would the unit function better as far as locking up just with a little chater around corners? Could that further ruin my posi unit? What about a posi unit from a 4th gen, the zexel torsen unit? Are they rebuildable? Will the carrier bolt up in a 3rd gen rear?

Zexels aren't rebuildable as they don't need to be rebuilt. Nothing wears out, no clutch packs inside it.
Yea, carrier bolts in, you just need matching 28 spline axles from a 1990-1992 third gen, or aftermarket. Boy this is a familiar topic to be discussing.... Check the other thread about this very topic that's on now. online170's thread

Yeah, if you can manage to pick up a torsen unit for a good price somewhere, that's definitely a good way to go. Like Sonix said, there's no clutches to wear out, they use gears just like the true-trac units. If it's not overly abused, a torsen should last indefinitely. If you still have an 87 rear, you'll need to hunt up a set of the 90-92, 28 spline axles too.

How good is the Detroit TrueTrac differential? I have heard of it, but does it take one wheel to spin before it engages, or does it do it real quickly?

so my 3:08 is a 2 series carrier??

so my 3:08 is a 2 series carrier??[/quote]

Correct. 3.23 is the start of the 3 series carrier. Kinda screwy that the 3.08's are 2 series, but that's the way it is.
----------
You could send Sonix a PM and ask him. He just installed a True Trac in his car not long ago. I would imagine it engages quickly though. I know the Torsens do, and the True Tracs are a very similar design.

I just finished installing mine a few weekends ago, the rear end is still up on sawhorses and it'll be until april when the thaw hits before I get a chance to try it.

I also am look for a good way out, I have a 89 IROCZ with a 405 and a 700r4 trans. looking for a rear that will not brake. Don't know anything about rears (this is the third one in the car).

Wow, if you're already on your third replacement rear, it sounds like you're putting out enough power to justify spending the cash on an aftermarket 12 bolt or 9 inch from Moser Engineering. They cost about $2K-$2.5K, but they're a direct bolt in, and they're WAY stronger than the factory rears. Also, if you can dig up your own center section and gears, you can just buy the bare housing and axles for a bit less than $1K. When you consider the cost to keep replacing the weak factory rears, or to beef up one that still stands a real good chance of breaking anyways, the Moser rears are money well spent. Attempting to retrofit a different and stronger junkyard rear is more of a PITA than it's worth due to the difficulty of trying to adapt the factory torque arm to one.

youll have bad wheel hop on turns if u dont add additive. yes itll hurt the posi, you could burn up the clutch packs, zexel arent rebuildable and will last a long time if you dont do any racing, and its just a daily driver

I upgraded to a True Trac unit with a 3.42 gear with a Trick Flow girdle and studs back in March. Great results so far, lots of hard launches at the track from a dig, dead hooking on ET streets making over 400 ft lbs to the tires.