Is this for real? '70 12 bolt

Discussion in 'Auctions and Online Sales' started by hwprouty, Mar 16, 2021.

  1. hwprouty

    hwprouty Member

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    I've looked at the charts and see it was a 3:55 ratio non posi, built by Detroit Gear but what does the 'Z' designate? C OW 0210 G Z
     
  2. badazz81z28

    badazz81z28 Veteran Member

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    pic?
     
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  3. Gary S

    Gary S Administrator Lifetime Gold Member

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    The 3.55 was available on the Camaro only on the SS396/L78, and that car required posi. That leads me to believe that a COW rear end is likely from a Firebird. I can't find a complete listing of Firebird drivetrain offerings, but the Trans Am option mandated posi just like the L78, so it isn't likely from a Trans Am. I don't know if the Formula or Esprit options mandated posi, so it could possible be from one of them.
     
  4. Rosster

    Rosster Veteran Member Gold Member

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    Yeah, typo by me. Sorry as said it’s a 3.55 non posi so likely from a firebird .
     
  5. hwprouty

    hwprouty Member

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    Mystery solved!
    Badazz81z28 had me go look again, it's a 2 not a Z...
    My eyes aren't so good and overtime made it worse I guess! IMG_1672[1].JPG So it was made on second shift, something I'm well aware of!!
     
  6. mallard

    mallard Veteran Member

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    I hadn’t thought about it in years but I’m imagining trying to keep a right rear tire on a non-posi ‘70 350 4spd. :bowtie:
     
    Last edited: Mar 18, 2021
  7. hwprouty

    hwprouty Member

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    camaro1.jpg Um yes, Here's proof!!
     
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  8. hwprouty

    hwprouty Member

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    I have storie's from that pic. If there's interest I'll single finger type some posts from work this weekend!
    At work I have 8 hours of boredom, you guys help me out.
    And V8Buick.com. Good group of folks
     
  9. hd_cat

    hd_cat Member

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  10. 70RamAirIII

    70RamAirIII Pontiac-aholic

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    I'm going to piggy-back on some of the replies here;
    Yup, craigslist add for a COZ coded (originally contained a 3.73:1 posi) Firebird/Camaro 12 bolt housing is legit.

    From what I have read, that's one of the most desirable setups to have, and if you have an original 3.73: posi car, and you want to built it right - that's the way to go.
    I understand the comments on being able to buy new but if it's a desirable car and you put an aftermarket rear end in it versus an original rear end you will see a difference in the selling price.

    I would think that no one would be so anal as to insist on all original parts inside - that seems to be in the same vein as suggesting a car is worth more if it's correct or numbers engine uses OE cast pistons, and an OE timing gear set instead of newer better replacements - it's good for a chuckle when you want to make fun of people who are trying to get their car numbers correct, but it's not entirely accurate.

    To anyone who might appreciate seeing this, here are the codes used on the 1970 Firebirds with twelve bolt differentials (I'm going on memory here as to which gear set was 12 bolt versus 10 bolt, so please correct me if I make a typo):
    COS = 3.07 open
    COT = 3.07 posi
    COU = 3.31 open
    COV = 3.31 posi
    COW = 3.55 open
    COX = 3.55 posi
    COZ = 3.73 posi

    Also, I do not know when a Camaro came with a posi, but as far as Firebirds are concerned, that item only came standard on the Trans Am - it was optional on the Formula.

    I have recently learned that Camaro's and Firebirds could share differential housings, but there were some Camaro specific one - those had leaf spring perches for a four left spring - Firebirds only used a three leaf spring. I do not know if the Camaro housings had different codes.
     
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