Posi replacement

[JoeliusZ28]

With 110k miles of "spirited" driving my posi is about expired. Anyone know of a good writeup for replacing it and where I can source the parts?

[NullHead]

DTS for parts. 10 bolt?

[JoeliusZ28]

Yes its the factory 10 bolt in my 95 Z

[Gregs_gsxr]

DTS is great.

[NullHead]

Honestly, I went off Google when I put the Detroit locker in my firebird. The specs are all usually the same, and all the guides I seen seem to all say about the same thing. The one thing that wasn't immediately clear to me was how to check carrier side bearing preload. It involves math, but it's done separately than pinion bearing preload. Then when they're both calculated you'll end up with a total turning torque.

Dunno where the disconnect happened in my brain, but I was 90% done when I realised I had to tighten up the carrier bearing preload.

[JoeliusZ28]

Bump. Still havent found any good writeups with pictures. Would really like to know what im doing ahead of time. I'm all for diving into a project and learning but when it comes to axles this thing has been a trooper i dont want to "disturb" anything i dont have to.

[Boost Addict]

So you're just changing the carrier? Not a complete rebuild?

[JoeliusZ28]

I want to replace just the posi. While the rear end is leaking and could use a rebuild id rather it just leak and stay working than risk messing up what is apparently a well-set gearlash or whatever the technical term is. Hundreds or even thousands of holeshots/powershifts on this thing and its still quiet as a church mouse and there is no slack in it or any other sign of it failing.

...But thats all assuming i can remove the posi without disturbing the gearset. If thats not possible then i might as well do the full rebuild, which is why a writeup would be helpful.

[JoeliusZ28]

[MENTION=709]bri2203[/MENTION] what would you recommend here?

[hoogiesngrinderz]

A new carrier will not fit exactly like the old one. Pinion depth should be the same but you will have to shim the carrier to achieve the same backlash.

[JoeliusZ28]

A new carrier will not fit exactly like the old one. Pinion depth should be the same but you will have to shim the carrier to achieve the same backlash.

Ok so let me demonstrate my noobness here... Why would a replacement carrier not have the same dimensions as the existing one?

[hoogiesngrinderz]

It very well could be the same dimensions, but in reality you're talking about setting it up within +/- .001 of an inch. You have to factor in overall length of the carrier and where the face is that the ring gear bolts against. Then you have to factor in bearing preload.

I got extremely lucky when I put that Detroit TruTrac into the v6 3.42 open rear I purchased. I was able to use the original shims but I had to swap them around to get an acceptable backlash. Preload was nearly spot on, meaning the overall length was close to OEM but ring gear was sitting too close to the pinion.

[JoeliusZ28]

Well my understanding must be way out in left field then... I had the impression from a number of threads this is was bolt-out/in job. If i gotta mess with shims i might as well do the whole thing, not sure i want to get into that right now or at all

[JoeliusZ28]

Maybe before i get too invested here, would low fluid could be a cause of the posi not holding? I wanted to check on this before i put the car away for the season but i didnt get that opportunity. I topped it off at the beginning of the season (edit: actually drained / refilled) like i usually do, possible it leaked more this season than in years past.

[hoogiesngrinderz]

The cones are likely wearing out but you could try the 4oz GM additive, even if the gear oil was formulated for limited slip.

You might be able to get away with a simple swap if you don't mind the backlash being a few thousandths off from how it came apart.