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'91 G80/drum rear end combo....9" or 10"?

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Old 01-19-2005, 12:21 PM
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Car: 1994 Trans Am
Engine: LT1
Transmission: Auto
Axle/Gears: 3.23
'91 G80/drum rear end combo....9" or 10"?

Does that combo sound like a 9" or a 10"? Reason why I ask is because the car, again the car isn't in my possession yet, is because if the car has crappy 2.77 or whatever crappy gears, I'd like to swap it out for like 3.73 or 3.42 disc instead. Obviously, the discs are for aesthetics and if it's too much trouble, it wouldn't be a big deal to keep the drums.

Do they make 3.73's in both 9 and 10inch rears? What about 3.42's or 3.45's?

Sorry for such a newb question, but I need to know in case I come across a good deal.

Could I use a 4th gen rear with discs, if it had the gearing I liked? I know they aren't the same size as 3rds and require spacers for wheels, but I would want to get 4th gen WS6 wheels anyway.

Let me know.

Thanks, Kevin
Old 01-19-2005, 01:15 PM
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9" or a 10"


Do you mean "9-bolt or 10-bolt"?

If so, it's a 10-bolt. Last year for the 9-bolt was 89.
Old 01-19-2005, 01:22 PM
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Yeah, that's what I meant. So then what does a "9 inch rear" mean? I've heard these exact words before, but I did mean 9 bolt and 10 bolt not inches. Whoops!

So '89 was the last year huh? I have a 10 bolt, is that bad for performance? Will it break under stress, say with DR's or slicks?

I've been searching since I posted this thread and it looks like I will try and find a 9bolt or another 10bolt with rear discs and 3.42's. All I need is a PV.

Thanks.
Old 01-19-2005, 01:25 PM
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A 9" is made by F*rd; that refers to the ring gear diameter. GM rears are usually differentiated (excuse the pun) by the number of bolts holding the cover on.
Old 01-19-2005, 02:32 PM
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Yes, that explains why I never hear 9 inch chevy rear end. Thanks. I'm now a bit smarter.

Okay, I asked the guy I'm buying the car from for the RPO codes and here's what I found out:

It has aluminum drums (rare & lightweight!) and the aluminum Driveshaft, and LSD!!

But the flipside is it has 2.73's And like you said, '89 was the last year to have the 9-bolt.

So I can simply swap out the gears right? Where can I get either 3.42's or 3.73's at?
Old 01-19-2005, 03:56 PM
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Not so quick on your Gear swap. Its not as easy as changing your oil. Do a search on this subject, there were posts by someone else who wanted to do the same thing. And he was not a happy camper after being told of the headaches to be encountered.
Old 01-19-2005, 10:30 PM
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In my opinion, for the same price as new gears, you're better off buying a 10-bolt out of a 4th gen, especially if you want to run 4th gen wheels in the future. You'll get disc brakes that brake much better, and you'll get better gears (assuming the rear you buy has the ones you want!...my '98 Trans Am rear had 2.73s!!)

If you get lucky, you can get one out of an optioned SS car that has a stronger differential as well.
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