I think my GN has been raped....

[deputydawg]

I took my GN out the other day and got on it just to see what it would do.....sonofabich its fast. Only one problem, only the passenger side tire spun and left a black mark. I am beginning to suspect the posi rearend was taken out. I know my GN was wrecked at one time and while under it I noticed the junk yard yellow marker on the Diff cover. Am I screwed or can I just change the internals of the rearend to make it a posi---or do I need to hunt down a stock GN rearend?

[kenmosher]

First step ... make sure it's an 8.5" rear end ... if they swapped in a 7.5" rear, then you have a different problem.

http://www.gnttype.org/numbers/axcodes.html

If it is an 8.5", it could just be the clutches are shot (about $100 rebuild) or you may need to swap in a new posi unit (if missing or too far gone) which is about $400. Auburn, Eaton, etc. make replacement sections.

[Keller]

First, check the sticker in the trunk for code "G80". If you have it, then there is a chance that there may be (or might have been) a posi to begin with. If not, you never had one at all.

[deputydawg]

of course, the sticker is gone......I took a pic of the rear end. Can anyone tell me which rear end this is?

[novaderrik]

that looks like a 7.5 rear to me..
which is bad.
good luck finding the proper 8.5 to put in there. a good place to start would be to search for a rusted out Monte SS that you can buy cheap, and hopefully it will have an 8.5 under it. or shell out the $$$ for a GN rear end- which will probably be more than the cost of a complete rusted out Monte SS.

[Keller]

Monte SS's have 7 5/8" rear ends.

You would need to find a GN/TR or a Olds 442. The 442's have 3.73 gears, but 8.5" setups.

[novaderrik]

i don't think the 7 5/8" rear came out until the early 90's when the Camaro got re-done, but i could be wrong.
and i've seen several Monte SS's that had 8.5's under them. maybe if you got a posi in the SS, you got the 8.5, non-posi got the 7.5 or something screwy like that.
i do know that at the boneyard i used to wander around on weekends (when i lived 4 miles away from it), whenever i saw a Monte SS body there, the rear was always taken out before it made it to the yard, and they always had some writing on the 1/4 panel that said something like "8.5 3.42 posi".

[kenmosher]

That's a 7.5" from the picture ...

I've never seen an 8.5" in the Montes?? According to Eric Fisher (who has worked in GM parts since the early 80s) it was never offered in the Monte SS, just the 7.5"?

[Keller]

From http://www.montecarloss.com/SSThunder/stock.html

"New in 1985 was the 4-speed automatic transmission (THM 200-4R) in which 4th gear was a 0.67:1 overdrive. The rear axle was changed to a 7-5/8 inch ring-gear, with a new ratio of 3.73:1 from a 7.5 inch, 3.42:1 gear."

So before '85 they had the 7.5", and '85 and later they had the 7.625" to handle all the power of the new motor.

Still, no 8.5".

[Keller]

Originally Posted by deputydawg

I took a pic of the rear end.

The little 'fangs' hanging down give it away as a 7.5". See http://dyeager535.topcities.com/diffid.html

That exhaust looks like one from a stock V6 or V8 Regal made in a muffler shop. I don't even think the stock system was that small from the factory. Maybe I'm just getting old. Get that replaced and you'll have that rear end scattered all over the pavement in no time!