12 bolt posi from my 69 g.s.400

Discussion in 'Got gears?' started by gsgeorge3, Oct 22, 2018.

  1. gsgeorge3

    gsgeorge3 Silver Level contributor

    I have the original 12 bolt posi from my 69 g.s. 400. Im planning on going through it. I would like to know how to i.d. which rear end it is. Any help would be appreciated!
    Thanks,
    George
     
  2. Ken Mild

    Ken Mild King of 18 Year Resto's

    When you say "which rearend" you mean the ratio? Or what make? If it was a Canada car then the 12 bolt was born there (as long as it was never swapped out) and it is a Chevy 12 bolt.

    I counted the ring and pinion gears in my 12 bolt (not a posi though) and it is a 3.08. From my research the U.S. 10 bolt comparable ratio would have been 2.93.
     
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  3. gsgeorge3

    gsgeorge3 Silver Level contributor

    Thanks, ken, I should have been more specific. It was a Canadian built car, so I believe it's the rear end that it was born with. I am wanting to know the make.
    George
     
  4. hugger

    hugger Well-Known Member

    Only one 12bolt, other than the oldsmobile version which is a boat anchor. But what you have if its correct to the car, is a passenger car GM 12bolt 8.875, order parts accordingly
     
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  5. gsgeorge3

    gsgeorge3 Silver Level contributor

    Thanks, hugger.
    George
     
  6. BrianTrick

    BrianTrick Brian Trick

    780677FB-8EB1-4E0B-B5A5-504FFCFA3090.jpeg EEC8CF13-96A4-409E-89D9-BB9ED81FC33B.jpeg 897BB21C-C531-498F-8A9B-A64553944F44.jpeg 38387E43-A737-423E-8485-03B789D5BA35.jpeg D40FF1D5-51AC-49A6-BC12-02C1C7763488.jpeg 670CD043-2B08-4270-B674-A33F33EFFC1A.jpeg 914E0185-69F6-4DFD-A188-964DB1C90691.jpeg This is what a 12-bolt Chevy rear looks like:
    The only difference with yours would be the yoke. Your 12-bolt will have a BOP style yoke,which takes the 3R u-joint,and is secured with u-bolts & nuts.
     
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  7. Ken Mild

    Ken Mild King of 18 Year Resto's

    Brian that is quite the specimen there. Almost too nice to put in!
     
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  8. gsgeorge3

    gsgeorge3 Silver Level contributor

    That is a beautiful thing there.....and that is what mine is......with the positraction tag on the side
     
  9. monzaz

    monzaz Jim

    Tag on the side? Red by the fill plug or on the rear cover?
     
  10. BrianTrick

    BrianTrick Brian Trick

    Some have a fill plug with a collar that holds the red plastic tags.
     
  11. gsgeorge3

    gsgeorge3 Silver Level contributor

    jim,
    red, on the plug on the side, 1/4 pie shaped.
     
  12. monzaz

    monzaz Jim

    Yep 12 bolt chevy have that plastic red 1/4 pie shaped limited slip fluid tag and special fill plug mushroom head to hold it in place. .... not on the rear cover stainless tag
     

    Attached Files:

  13. Ken Mild

    Ken Mild King of 18 Year Resto's

    What's the proper location for this red tag. Can't believe after almost 34 years of owning this car I never knew this red tag was correct for my 12 bolt. (I don't have a posi but when I convert I'll want this correct tag).
     
  14. BrianTrick

    BrianTrick Brian Trick

    Some of the 12-bolts don’t have the mushroomed full plug to hold that red tag. The one I pictured didn’t have that plug,and had the typical bent,twisted cover tag.
     
  15. monzaz

    monzaz Jim

    I would think the BOP cars with 12 bolt Chevy from Canada would get the metal tag ... All I know is Chevy got the red tag with the limited slip. After 1972 1973 I would say all reas got the steel / stainless tag as this was the CORP era .... everyone used the same rear. I know 8.5 BOP had bolt in axle and Chevy had c-clips still till the mid 70's. Also I think the 1971 1972 GTO received the 12 bolt Chevy rear as there high performance option too.
    I do not worry about details like that as that is the customers deal for show resto parts... I deal with making them last. I deal with drag racers and custom rears for BIG WAGON WHEEL crazy city cars from Cleveland etc...lol .

    Jim
    J D Race
     
  16. Bigpig455

    Bigpig455 Fastest of the slow....

    I didnt even think of the Donk/Box/ Bubble crowd... what do they have to run to make those cars streetable? 4.88's?
     
  17. BrianTrick

    BrianTrick Brian Trick

    Most people are not particular about the minor details like that,but if I am doing a concours rebuild,I have to make it exactly how it was. I remember doing a few 1970 LS6 codes rears,and I took a lot of pictures before and during the process,so it ended up the same way again. I remember one of those was done and sent to a guy in Australia.
    Those can be a lot more nerve-racking than just taking one and rebuilding it with the desired parts for the customer.
     
  18. Ken Mild

    Ken Mild King of 18 Year Resto's

    Better yet why would you need a posi with 30 inch wheels?
     
  19. monzaz

    monzaz Jim

    And the reason I do not do Numbers on rears anymore... Number guys have driven me crazy for 30 years. I am glad to be out of original 12 bolt housings... lol. They all wanted a specific number for the restoration and then wanted to pay minimum money for the build...lol. Or they just wanted a housing for cheap after i did all the work to find them...
    You can have all that all day long. Too old and do not want to deal with it anymore.
    Might switch over to little aluminum Jr dragster motors.... They sell for 4500.00 ... God I am in the wrong business lifting this heavy stuff. :D

    30" wheel posi ... yep I do not know either but the pay and I build. PLUS they pull the rear and I do not need to be under a rust bucket.

    I am down to custom rears and Muscle car rears and drag race Rears. Nothing else ... No 4x4 or commercial etc. Thank God.

    Jim
    J D
     
  20. BrianTrick

    BrianTrick Brian Trick

    I would rather have a 2:56 non-posi and do a custom build,but there were a few odd occasions where I ended up with some real rare and valuable ones,like the 70 LS6 ones.
    That was the big reason the guy from Australia bought mine. It was exactly what he needed in every way. Correct codes,build dates,etc. He probably paid more to freight it to Australia than what he actually paid for the rear.
     

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