Hey guys,

I wanted to go POSI and Disc Brakes, and change my gear ratio to 3.42 but instead, I have the opportunity to buy a rear end from a 91 GTA.
This rear end has EVERYthing I could want, IMO, and more. Price is $350, can you tell me if it's worth it for one and two, will it direct fit into my 87 Trans Am HI 5.0.

Details (from seller):

just removed this from a 1991 GTA ,Worked great ,no issues,Complete with emergency brake cables and torque arm also rear sway bar is still intact. 3.42 gear ratio.

 

Are the pics working? I think you may have to click to view them..

 

Pics didn't seem to work. Should be a direct swap besides maybe brake lines. It should have 28 spline axles instead of the '89 and older 26 spline rears. Hopefully the posi carrier isn't worn out but you won't really have a way of knowing until after you've tried it out. Good luck.

 

Pics are fixed, is $350 a good price if everything is working?

Do I need to do anything to prep my car?
My 87 is completely being rebuilt so It won't be an issue.

His feedback rating is 100% over almost 2,000 transactions with muscle car parts.

 

BUMP:

I got him down to $300 on the price. Can any of you guys look at the pics real quick and let me know if this is a good deal, and give me an example of anymore pics I should have him take of the inside (I know I seen in a thread pics of the cone, but I don't remember thread, can anyone get me that pic so I can send to him as an example)?

Again: This is from a 1991 GTA and it's POSI, 3.42 Gears, Disc Breaks and Sway Bar, with all brake cables still attached. Says it was pulled working and he has great feedback and reputation in muscle car parts.

Also: Is this just a plan swap in/out bolt right up?

 

It should bolt right up. Can't tell by the pics but the calipers should be the newer '89+ style. I believe they should say PBR on them. The older '88 and older rear discs rarely even work. The other thing I would confirm before buying is the ratio. Only good way is to have him pull the cover and send you a picture of the numbers stamped on the ring gear. Then you can make sure it's a posi too.

 

Thanks, yes, I am awaiting full pictures of the inside before I send payment. I will get apic of the #'s and post it, there was another thread with pictures on how to tell something about the cones?? I am not good with rear ends, so sorry .

 

The only way you will be able to check the cones is to disassemble the differential. I don't think the Auburn has windows like the Borg Warner to check the cone depth.

One roough way to check for cone wear is to see how much axle end play it has. This might be a little hard to do with the disc brakes installed. Just push and pull on the axle to see how far it moves in and out. As the cones wear the axle end play will increase.

 

For what it's worth, I've ran two different used BW 9 bolts and both diffs were pretty worn out. I never knew if it was going to spin two tires or one. Around corners it would only spin the inside then the 1-2 shift would sometimes shock both tires and break the back end loose. Caught me off guard a couple times and spun me right around in traffic back in the day! I'm not sure if the Auburns in the 10 bolts are any different, but I guess my point is don't be expecting a super tight diff. It'll still be a hell of an upgrade from an open diff either way. And $300 is a pretty good deal if it checks out. Just a new posi is at least $150 more than the whole thing. Hope it works out for ya.

 

It looks to be a 10 bolt.
Was the GTA a 5speed ?
That's the only way it would have 3.42 (factory), if it was a auto it will be 3.23 gear.
I thought the 90-92 10bolts have clutches in the diff? Its been awhile since I tore into 1 of those.

IIRC, you may have to do something with the E-brake and the cable hookup may be a bit different on the car body.

 

Right; 90-92 AFAIK are all Auburn. {insert gagging puking barfing noises to your taste here}

The one EXACTLY like you have in your pic that I have in my 83 right now, right down to the story being that it was from a 91 GTA and is all ate up with salt-belt rust, came to me with an Auburn (threw in the trash) with 3.23 gears (threw in the trash) and wore-out axles. (threw in the trash) Put an Eaton and the lame stock gears for my car (3.73) and some decent axles (Superior EV 10-4) in it. TERRIFIC rear end now.

F a bunch of what gears, axles, & posi it has. Buy it. It's THE ABSOLUTE BEST POSSIBLE 3rd gen 10-bolt core you can get. Build it into what you want. This is no different from buying some truck 350 with double-hump or Vortec heads and complaining that the spark plugs are lame; big whup. FIX IT. Not a problem. It's THE PERFECT core to sink money into.

 

I don't know JACK about read-ends. That's why I wanted to just buy one that had all my specs. Is it pretty easy to fix the rust on this?

 

Ditto, I just finished rebuilding the 10 bolt axle I got from a 91 formula, exactly the same as the one you're looking at.
Mine was in great shape, but since the age and and condition of bearings and carrier were unknown, i stripped it, blasted, painted w POR15 , replaced all bearings and replaced the carrier with a Truetrac posi. Haven't put the brakes back on yet. I think the one issue you have to bolt in the axle is the brakes. The ebrake cables are different and I think you also need the proportioning valve for the different rear calipers. I took all that from the 91 as well, maybe you can get those parts too.

 

Mine, I tore COMPLETELY down (obviously, since I put gears in it, wasn't much left to tear down after getting it ready for that) and had LCARBs welded to it and had the tubes welded up; then had it powder-coated. Still is a bit pitted but at least doesn't look like it's been a ship anchor for half a century.