What rear fits my 1966?
Replacing my rear in my 66 GTO (late 66 style rear, according to measurements), and I am trying to figure out what years will bolt in? I am looking at a 1970 rear that is for sale on this site, but the spring perches are different and before I buy I want to make sure it will fit. I have googled and found very little info. Some places say anything from 72 and earlier will bolt in. Others say only 67 and earlier. Does anyone have any real experience in swapping in a newer rear into a 66? I know I could go custom ford 9", but I am working with a budget...(yes, funny, I know)
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Do you not have a rear now?
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68-72 rearends are wider. By 1 inch I believe. They physically bolt in but generally you need offset wheels to compensate. Skinny stock wheels and tires can usually still fit but look a little funky on 67 and earlier a bodies with a rear that's too wide.
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http://www.iegtoclub.com/Tech%20Lib/...tification.htm |
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I have a '64 GTO and have had 3 different rears in it. All three rear ends were the 1" wider rear of the later A bodies. I was still able to run 255/60/15's with all 3 rear ends using stock GM 15x7" rims with 4.25" backspacing.
The first 2 were 8.2" Pontiac 10 bolts. The current one is a '68 Chevy A body 12 bolt. That '70 rear end will work fine in your car, as long as you have rims with proper backspacing. |
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I have a 66 GTO with a 70 GTO rear housing. Using my stock Rally I wheels no issues. If technically 1" wider, thans only 1/2" per side. Good Luck
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1966-72 Pontiac A-body uses the same rearend width.
1964-65 was 1" narrower overall width. Only 1964-66 uses the bolted down springs. For '66, the 10 bolt center casting was p/n 9783393. For '67, the 10 bolt center casting was p/n 9783393 (no change). This casting was also used for the '67 Firebird rear end assembly, even though the axle tubes were different and the upper ears were not needed/used. Chevy A-body was different, 1964-67 was the narrower style, 1968-72 was 1" wider width. Also, NO need to replace the springs using a 1967 and later A-body rearend on 1966 and earlier. 1964-66 A-bodies uses rear springs with one tangential end and one pig tail end. 1967-72 A-bodies uses rear springs with pig tail on both ends and the upper end bolted to the frame. FWIW |
I would just get a new auburn posi unit and new gears .
The shop that you have do the gear and posi install should weld the axle tubes in better and while there at it rede the upper control repair if it looks like it needs it. There’s no sense in shelling out money for a used posi rear and stuffing it with new parts if yours is still usable! Any original 8.2” rear with what maybe a good posi will not be good for long anyway and then your almost back at square one anyway! |
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WHAT'S the PURPOSE BUILD of the car??? thats the first thing that I always ask when someone's considering a differential build or total r/e replacement? Second, from hands on experience, the #1 cause for edges of teeth getting chipped of a ring or pinion gear is a loose pinion, the pinion no longer being properly located, but moving slightly too & fro in its carrier bearing bores upon coast & accel. Can not relay how many 8 or 9 tooth pinion gear sets that I've taken out, that the R&P blew up from light coast to full throttle acceleration. 3rd, In instances where there is a gob more Torque being abruptly loaded to a weak design center housing rear, than the rear was designed for, there can be pinion deflection. This becomes more evident with lot of torque & really low gear sets, i.e; 4.33, 4.56, 4.88's. |
By the time you spend all this money tracking down and rebuilding an inferior 8.2 you can buy a 9 inch from quick performance for not much more. You’ll be surprised
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Another option OPH may explain better than me is a 1971-72 Olds or Buick A 8.5"; superior to a 8.2 but cheaper than a 12 bolt and you get bolt in axles.
I have one in my 71 with a Detroit TruTrac. IIRC you may need to mod the prop shaft. |
Regarding the 9 inch from quick performance, the price is tempting, but there are also a lot of high torque pontiacs running around with old 8.2 rears.
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Quite frankly I've never had much luck with the 8.2 when the horsepower gets around 400 and sticky tires are used. If you are just looking to drive around and not thrash it you can go back with another 8.2, BUT if you have ideas of getting a little aggressive, do yourself a favor and get an 8.5, 12 bolt or 9".....you'll be money ahead in the long run!
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