I have an 84 z28 and it was a 5 speed. Ive been told that means it has 3.73 gears but it is clear that there is either no posi or the posi has worn out. I was curious what would be a good aftermarket posi unit for a cheap price, or atleast reasonable price. I'ce sseen SLP has one for 88+ models, Im curious as to if I could makle that one work for my car with some modification. Any help would be appreciated, thanks.

It would work if you changed over to 28 spline axle shafts
your 84 has 26 splines.

Considering you have some very good gears, I would guess the best alternative for you might be the Powertrax Lock Right or No Slip Traction system. I haven't tried it yet (it's presently on my mod list) but have read some very good reviews.

It replaces the spider gears in the open diff. and makes the rear a locker when power is applied, and from what I've read its a very easy install. If you do a search in this forum you should find some reviews on it.

I bought a kickass 26 spline auburn pro on ebay for $86 + $20 freight (heavy), you have to be careful though there are a bunch of POS posi's on there that wont be any better than yours...

yes, def. watch e-bay, i got my Eaton Posi for $102 after shipping.

I bought an Auburn Posi unit for my car and I couldn't be happier with it. I will have to take a picture of the slab that I layed yesterday. This is a very strong unit and reasonably priced brand new. If you buy one from ebay or get one used somewhere else, you are chancing failure. Someone else has all ready had there way with it. Just my opinion.

i wouldn't buy a used auburn, the eaton however is rebuildable, so even if someone really whales on it, you can put new discs in, new springs in, new races in, new bearings on it, ect.

So try and get a Auburn por or Eaton posi. I'm curious when searching for it, what should the specs be for it. As far size goes, I'm completely unfamiliar with posi, this is the first time I've had to buy one.

Well you need to find out what you have in there right now. There are 2 different rearend housings for our cars. 3 if you count the borg warner rearend. But the 7-5/8" rearend have 2 different series housings. The series 2 housing holds gear ratios from 3.08:1 and numerically lower and the series 3 holds gears from 3.23:1 and numerically higher. A series 2 carrier will not work with a series 3 housing and vise versa. Figure out which one you have and then you can figure out which unit you need.

I was thinking of going the same route with an Auburn posi with Richmond gears. I'm kinda new to the posi myself and heard that you're speedo will be off once you install the new gears. How would you go about correcting this? I'd be going from an open ended rear to a 3.42 so there will be some issues with this.

either way remember this when buying, the "ratcheting" posi's suck, not to be confused with a detroit locker which I doubt was ever made for a 7.5. This "ratchet" style is super weak and will usually break in the case or ratchet area. here is a pic to tell the two apart...

Is it possible for me to go from an open end to a posi rear? Some people I've talked to say yes and others say no. I have an open ended rear and have someone in line to buy an Auburn posi unit and Richmond gears. Doesn't that just bolt up or would I need to get a used posi rear end?

you can install those into your rear end but its not a bolt in process, you need a tool for setting pinion depth ($90-$300), one for checking backlash ($40-$50), and one for setting pinion bearing preload ($20-$150).

The low end of that price spectrum is for tools to be used by very experienced installers.

most shops charge $250 to $350 install labor for gears. They make no promisses on reliability if used parts are installed or if all bearings are not replaced. reinstallation of used gears where the pinion depth and backlash are even a thousanth or so off from the way they were previously installed (but still within spec) can cause a horrible howl. I have installed 30 or 40 (guess) sets of gears on everything from a 7.5 GM to a huge dana 1 ton.

Well, all the stuff I am going to buy is brand new, so would it be wise to get a used posi rear to install them in or just put them in my open ended rear?

some shops cut $50 off the price for a carry in rear

and your car doesnt have to be down as long either, just a rear swap and drive...

i had a open 3.23 rear end with 26 spline axels. i went to jegs ordered the Auburn differential posi for 329.99 and got the richmond Mega pack install kit for 128.99 and i had a local guy ( i trust him alot, he used to own my car and builds some sick motors and drag cars) and so far im very happy with it now, i need new gears becuz either the carrier bearings or pinon bearing is warped and caused the teeth on the ring gear to get a sharp edge but other then that im happy.

and ive read and reread that the 7 1/2'' and 7 5/8'' rear ends are basiclly the same excupt for the housing, everything internaly can be exchanged between the 2 housings.

Everything I've read says that the 7.5 and 7.65 rears are the same internally. (of course it is different beween F-bodies, A-Bodies, and S-trucks), but that the internals are all the same

26 and 28 spline axles were/are available for them

The big difference is in the carriers. An axle equipped with 3.08 or lower (like 2.77) uses a different carrier than an axle originally equipped with 3.23 or higher gear ratios. Of course, higher gear ratios are available for the 3.08 carrier.

Of course, none of this matters to me, because I have the 9-bolt. (with 2.77s goddamit!)

sharp edge in one spot or all the way around?

i think the machanic said all the teeth so yeah all around.

Gears were installed incorrectly then. not due to warpage or any other BS like that.

www.reiderracing.com makes a drop in locker-type unit for the 7.5. Just pull out the retaining bolt (if it's not broken like most) pull the axles out a little, remove the spider gears, shove the axles back in and button it up. Takes about 2hrs if you're slow.

this thing? http://www.reiderracing.com/ezlocker.htm they dont seem to disengage or unlock on the cars ive seen them installed in they act like a mini spool 90% of the time.

And they're noisy, but that's beside the point. the original post said cheap or at least reasonable price.
My experience has been that once you open the rearend up, you end up putting in the axle bearings and seals, what the heck, pinion and carrier bearings and while I'm here I might as well pony up for the hi dollar posi and Maybe I should go with the 4.11 gear change as well. Don't forget the girdle. My $350.00 projects eats up about a grand.
Trust me, buy it, drop it in and be happy.