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View Full Version : I think my GN has been raped....


deputydawg
03-18-2006, 10:51 PM
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
03-19-2006, 01:28 PM
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
03-19-2006, 02:14 PM
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
03-19-2006, 09:00 PM
of course, the sticker is gone......I took a pic of the rear end. Can anyone tell me which rear end this is?

novaderrik
03-25-2006, 02:19 AM
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
03-25-2006, 02:37 AM
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
03-25-2006, 02:50 AM
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
03-25-2006, 10:38 AM
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
03-25-2006, 11:23 AM
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 :crackup: power of the new motor.

Still, no 8.5".

Keller
03-25-2006, 11:28 AM
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! :loll:

deputydawg
03-28-2006, 03:56 AM
Okay, I am officially P.O.'ed. I am beginning to think I bought a complete basket case. I have been having a problem with the rear end not sitting centered under the car. I know the car has been wrecked at some point. I suspected the control arms were bent. I just replaced the lower control arms, and nothing. The rear end is still sitting more to the driver's side. Anyone have any ideas on what is wrong and how to fix it? :duh:

Keller
03-28-2006, 04:32 AM
Get it on a 4-wheel alignment machine or a frame alignment jig. There's no other way to really tell just by scratching your head.

deputydawg
03-28-2006, 03:36 PM
I just got back from the frame shop.....the frame is bent and will cost about 750 bucks to fix. Well, I guess the body work and paint will hold off...

JHensberry
03-28-2006, 08:55 PM
Sorry to hear that. Have had to put off things before. Atleast you were able to get the important/needed things done before throwing performace parts at it like other people have done. Start with the basics and reliability first and performace second and you will be a happy Buick owner.

deputydawg
03-28-2006, 11:43 PM
true, going to get the frame straightened, see what body work presents itself and go from there.