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#1
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Does anyone produce a 12 bolt for a 73-77 GP?
Does anyone produce a 12 bolt GM rear end for a 73-77 Grand Prix, specifically a 1976. I've searches the internet and the only thing I have found is a Moser M9 through Spohn. I'd prefer to keep a GM type rear end under my car if possible.
Thanks in advance |
#2
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Don't let the number of bolts fool you, the 8.5 is where I'd start
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#3
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I would give curry or moser a call directly.
I can't see the the A and G body being so different that they couldn't build one for you. I would think they would just need to adjust the tube length. You might have to add the spring perches yourself. |
#4
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The '73-77 A-body r/e housings have a wider spread on their cast in upper control arm perches than the perches cast into housings used in all previous ('64-72) A-body rears, that would mean a different casting of the center housing by an aftermarket mfg like Moser. The typical 12 bolt doesn't have the pinion support of an 8.5 rear, so the extra 3/8" diam of a 12 bolt ring gear isn't the deciding factor in comparing r/e strength. Neither is the extra 2 axle splines, as OEM 12 bolt axles flare up at the beginning of the axle splines. unless the 12 bolt rear has 40+ year old GM HD service pkg axles or quality aftermarket 12 bolt axles, stock c-clip axles are a problem point.
Desire to stay GM rear, one can build up the '73+ 8.5 A-body housing with custom 30 spline bolt-in axles & an Eaton posi unit. I've built several '73 A9 housing A-body rears that way, as well a few with 33 spline spools & Strange axles for track use. What is the Purpose Build of the car, that should be the determining factor. Footbraked 11-12 second street car? Heavy low 11 sec car leaving with on trans brake?
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Buzzards gotta eat... same as worms. |
#5
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Quote:
I know very little about upgrading rear ends so I don't know where to start and what would be good for the car and what would be a waste. I'd also prefer not to do any cutting on the original rear end. If I have to buy something from a different car to cut/weld up, I may go that route. |
#6
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There was a '10-bolt' with an 8-7/8" ring gear that was used on '73-'77 A-body wagons. Our '76 Buick A-body wagon had one.
Factory gears for that ranged from 2.56 to 3.23. |
#7
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I have this for sale... I bought this for my 77 GP in 1990. It is still brand new, 30 years old. Has never driven the car and only rolled maybe 100yds total. It is a Currie 9", was $4000 in 1990. It has 3.70 gears and a Ford Traction-Lock 4-pinion posi. I added Lincoln disc brakes after I bought it. This same rearend will still cost you $4000 today. Send me a pm if you are interested. (I don't know why the last pic uploaded upside down)
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Jeff Ianitello |
#8
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These did come in some GPS. My 75 has one from the factory. Aftermarket support is zero. Shame because they’re pretty strong. Mine has 31 spline axles but has C clips. Steepest gears are 3.42. There used to be a machine shop in Texas that made 3.55 gears for these to fit the most common 2.78-3.08 carrier. I upgraded mine from 2.56 open to 3.23 posi but searched for years to find good used gears and rebuilt carrier.
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#9
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Quote:
The ironic thing is my car actually came with a posi rear end (1 of only 3 options the car has on it.), but the gear is like a 2.27:1. I'd use the existing carrier, but I don't trust the 44 year old 28 spline axles with a 455 in a 4000# car running deep into the 12's. |
#10
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I have one of these 12 bolt ring gear, 10 bolt cover rears hanging in my shop if anyone is looking for one.
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#11
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What gear ratio?
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Jeff Ianitello |
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