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Discussion Starter · #1 ·
I have a 8.5 10 bolt w/posi and 332-1 gears out of a Grand National Buick in my 69 sport coup.
I am interested in a 66 12 bolt a guy has that has 355 & posi.
The 10 bolt has a very good clutches and no whine the 12 bolt "who knows".
The only reason I want the 12 bolt is that I hear the 66-67 were 1" narrower than the 68-72 and this would allow me to use a wider wheel.
Am I wrong?
wWats this 10 bolt worth in trade value? I have heard they are harder to find than a 12 bolt?
any input will be appreciated.
thanks T.C.
 

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If it is out of a GN, it would have 3.42 gears. I have seen those rear ends go for as much as $700. I have also seen 12 bolts go for that too. I would find out about the 12 boly condition, if it is good, sound like a fair trade to me. 8.5 rears are indeed hard to find



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1968 SS396 350 HP TURBO 400 4.11 POSI, TUXEDO BLACK
1979 Chevy Malibu, Restored
1978 Malibu Factory 4-speed No Option car
 

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Discussion Starter · #3 ·
Thanks MY68SSCHEVELLE:
It does have those numbers stamped on one of the axle tubes.
I guess I will have to make shure I am getting a good 12 bolt, because there is nothing wrong with the way my 10 works.
Just wanted to get those wide wheel/tires under there without cutting the flanges.
I have also heard that "C" clip eliminators will or can be installed as to shorten the rear? But I also hear they leak?
thanks again T.C.
 

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tc, you say you have the GN rear in there now? well its 51 1/2 inches wide. 64-67 rears are 53 1/2 wide. you'll be losing 1 inch on each side if so.
 

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Is the 8.5 in your car now? I thought GN rear ends had different mounting points for the control arms. If it isn't in your car right now then check the mounting points. If they are not the same then get rid of it and get the 12 bolt or something else that will fit.

Steve R.
 

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Discussion Starter · #7 ·
Thanks for the replys!!
Yes it is in the car now and it is a 8.5" I know this because I've had the cover off and checked the bolt size on the ring gear, also thinking back I believe it has 323 gears, does that sound correct for buick?
I also had a guy who knows the differences look at it (with the cover off) conferm it was a big 10 bolt and most likley out of a GN.
The numbers on the axle shaft match no chevy numbers I can find and it also has buick brake drums on it. If that means anything?
I will say that I have 10" rally wheels with 295/50 & 5" b.s. on the car now. The side walls will just barley rubb if I have someone in the rear seat or go around a corner to fast.
It has no hop bars so I couldnt say if the mounting lugs are in the correct position?
I will measure it tomorrow as I wont bother with the 12 bolt if this rear is narrower.
I dont know what other cars these big 10 bolts came in? I was told they came out in the mid 70's.
Mabe I have the best Im going get for a bolt in?
I'll measure it and post tomorrow.
thanks T.C.
 

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If you really have a GN rear in there you must have some funky looking control arms, because the G body rears' mounting angles are way off from the chevelle. If it looks like a clean bolt in with straight control arms, and it really is an 8.5 10 bolt, then it probably came from a 72 chevelle or monte carlo. Some 72s had em, I have had a few with the 8.5 but more often with the 8.2 10 bolt or 12 bolt.

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Dave (NY)
70 chevelle ss396 conv
66 chevelle ss396 hdp/conv
72 chevelle
TC member #493
Never forget Earnhardt!
 

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Discussion Starter · #9 ·
You guys are rite!
It measured aprox. 55" from plate to plate.
I know it has the large bolts on the ring gear and I know it is a 323 ratio. It also has the odd shape cover and the two ear looking things at the bottom of the center section. So is it a BOP? What are they worth?
I found some numbers before and had no luck with the I.D. of this. thats when I took the rear cover off to look at the bolts and put a fill plug in the cover as the no hop bars cover the one in the front.
Any help is appreciated T.C.
 

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Odd shaped how? is it round or round with "c" shaped cutouts on the ends? If it has the cutouts it is BOP, if it is round then it is chevy.



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Dave (NY)
70 chevelle ss396 conv
66 chevelle ss396 hdp/conv
72 chevelle
TC member #493
Never forget Earnhardt!
 

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I would say $150, $200 max. Unfortunately the BOP rear is not sought after, so prices are not as high as the chevy stuff.

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Dave (NY)
70 chevelle ss396 conv
66 chevelle ss396 hdp/conv
72 chevelle
TC member #493
Never forget Earnhardt!
 

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Discussion Starter · #13 ·
So what youre telling me is, that a 8.5" 10 bolt with a clutch pack posi. unit in good shape, with a decient gear ratio is only worth 200. max? I've heard these are as bullit proof as a 12 bolt? how can this be? You would pay more than that for a 7.5 10 bolt. Didnt chevy also have a rear with the odd shape cover? I believe it is called a "corporate" in fact looking at the gasket pics. in the Jeg's cat. the corporate is more round than the BOP rear looks to be "as mine is"
Thanks for you opinion.
T.C.
 

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TC, let me offer my .02 with regard to BOP rearends. Keep in mind that I'm no rearend specialist. I have a 8.5" 10 bolt out of a 72 olds station wagon. It was bought as a complete unit including posi (in good shape)
with new richmond 4.56 gears. I paid $550 for it about 4yrs ago. It has held up really well! The only thing I've done to it is replace the outer axle bearings (ran about $100 parts & bearings pressed on). While I won't argue that it is as strong as a 12 bolt I will say it ain't far behind. It also has the non c-clip axles (a good thing). With that said, I'll have to agree with Dave and say $200 for a good core (with posi not in need of a rebuild) is about right. Throw in $150-175 for new gears and labor for someone to set them up right and your right about at what I spent.

BTW, this rearend has withstood many 12.0 sec 1/4mi passes without a complaint.

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MY 67

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[This message has been edited by JOHN WILSON (edited 04-03-2001).]
 

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Sorry if I offended you with my value on the rear, but its not a guess...Ive been dealing with chevelles almost 15 years, and any 10 bolt posi rear with a high 3 gear doesnt sell for more than $200 at swap meets or locally. The BOP rear is generally not wanted, and is usually cheaper. Doesnt mean it is a bad rear, but popularity drives the prices of parts. 12 bolts bring the cash, 10 bolts dont.

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Dave (NY)
70 chevelle ss396 conv
66 chevelle ss396 hdp/conv
72 chevelle
TC member #493
Never forget Earnhardt!
 

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Discussion Starter · #16 ·
Dont misunderstand,I'm not upset.
I'm not convinced it's a bop yet and if it is that doesnt bother me either. I know the rear is good. I will just keep it and buy the 12 bolt outrite.
The rear will be out of the car in the next month or so, at that point I will find out exactly what it is. I think its a corporate myself? I really doesnt matter because I know it will hold up to my 468 with no problem.
thanks guys!!!!
T.C.
 
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