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Hot Rods 12 Bolt Chevy rears - Need info

Discussion in 'The Hokey Ass Message Board' started by Moonglow2, Oct 14, 2014.

  1. Moonglow2
    Joined: Feb 4, 2007
    Posts: 658

    Moonglow2
    Member

    Hi Guys, I need to pick your brains about a Chevy 12 bolt. When Powerblock TV built a '69 COPO Camaro replica, they narrowed a 12 bolt out of a 65-68 Impala. Now I am pretty familiar with all the engine options for those vehicles but not about the rear differentials. Is it true that any full size Impala from those years came equipped with a 12 bolt even if it only had a 283 in it? I have run up on a super deal on a 65 Super Sport Impala rear but need the real skinny before I lay down some cash. It's in a salvage yard and I will have to pay them to cut it out. Thanks, Nelson
     
  2. 1934coupe
    Joined: Feb 22, 2007
    Posts: 4,644

    1934coupe
    Member

    Can
    I can only comment on what I know, I have a 65 Impala rear and its a 12 bolt I had a 67 Belair 283 3 spd w/OD and it had a 10 bolt rear. I had a 65 Impala with a 409 and 4 speed it had a 12 bolt. Too bad your far away I want $150.00 for the rear I have. They are desirable because they have 11" brakes and a bigger bearing.

    Pat
     
  3. Moonglow2
    Joined: Feb 4, 2007
    Posts: 658

    Moonglow2
    Member

    Hi Pat, Thanks for the reply. Which engine was originally in your 65?
     
  4. Grahamsc
    Joined: May 13, 2014
    Posts: 466

    Grahamsc
    Member
    from Colorado

    I would go put eyes on the axel as someone could have changed it since 1965. image.jpg
     
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  5. txturbo
    Joined: Oct 23, 2009
    Posts: 1,771

    txturbo
    Member

    it could be 10 or 12 bolt. The only full size Chevy that always had a 12 bolt was the wagon. The wagons all came with the heavy duty suspension which specified a 12 bolt rearend.
     
  6. 1934coupe
    Joined: Feb 22, 2007
    Posts: 4,644

    1934coupe
    Member

    The rear I have I bought from a junk yard, it may have been a wagon as was mentioned previously. The 65 I had back in 70 had a 409 in it.

    Pat
     
  7. biscaynes
    Joined: Mar 16, 2008
    Posts: 1,649

    biscaynes
    Member

    could be a 10 or 12 bolt, count the cover bolts. i've seem them behind 283 2bbls. 12 bolts weren't just installed in wagons.
     
  8. k9racer
    Joined: Jan 20, 2003
    Posts: 3,091

    k9racer
    Member

    I have seen quite a few rears with 12 bolts holding on the cover and only have a 10 bolt carrier. Most were from BOP cars. I know we are talking about Chevrolet but many have been swaped around.. Bobby..
     
  9. If it's a true SS car I'd say it should be a 12 bolt. Back then you probably could have ordered a 12 bolt in plain Jane car if, you wanted to. I know a lot of the BOP 12 bolt rears had 10 bolt guts inside if them but, I'm not sure if all of them were like that. It's easy to tell the Chevy 12 bolts from the BOP 12 bolts just by looking at the cover.
    ImageUploadedByH.A.M.B.1413344655.999480.jpg

    BOP the left. Chevy on the right.


    Dustin
     
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  10. Oh..... And I wouldn't pay much for the BOP 12 bolt, since it's really a 10 bolt.... If that makes sense.


    Dustin
     
  11. GRX
    Joined: Mar 28, 2014
    Posts: 68

    GRX
    Member
    from MD

    Yep. Precisely why I got a Chevelle 12-bolt for my '69 GTO. :)
     
  12. Nope...Not all wagons were 12 bolt, and not all sedan were 10 bolt.
    Obviously a heavy duty option seen in many big block cars.
    I've seen wagons with 4 arm 10 bolts, 3 arm 10 bolts, and also some with 12 bolts.Not all 12 bolts were posi's either, but a lot were.
    65-70 is the same generation and what you 're looking for.
     
  13. 1970 GTO's had 12 bolts too.
     
  14. txturbo
    Joined: Oct 23, 2009
    Posts: 1,771

    txturbo
    Member

    I didn't say they were only installed in wagons.....I said wagons were the only full size chevy that they were ALWAYS installed in. All wagons got 12 bolts because all wagons came with the HD suspension as standard equipment, which required a 12 bolt also. Same applied to any other full size car that was optioned with the HD suspension.....even an inline 6.
    I conducted a survey about 15 years ago in a fullsize chevy internet group on this subject. The survey included over 100 cars. We determined that cars that had base engines of each engine size got 10 bolts. The upgrade engine in each size got a 12 bolt. The base engines were the 235 inline 6, the 195hp 283, the 250hp(not completely sure of the exact rating on this one) 327, the 325hp 396 and the 390hp 427. Then there were several options that required a 12 bolt be included which mixes up the logic. The HD suspension was one of them. Then there was also the control arms. Some had 3 some had 4.
     
    Last edited: Oct 15, 2014
  15. No.. again..saw plenty of wagons with 10 bolts..
    I had an Impala, 3 speed stick, 283/195, 10 bolt
     
  16. flux capacitor
    Joined: Sep 18, 2014
    Posts: 676

    flux capacitor
    Member

    The real COPO 12 bolt shares the 1/2 ton truck "HO33" gm ring gear not to be confused with the gm a, b, f, & x body cars 8.875 12 bolt, even though both have same ring gear diameter & number of bolts won't interchange. Friends dad owns Fred gibb 68 427 copo nova shipped as L78 car with th400 extra capacity clutch drum and ultra rare truck center section & heavier axle tubes on the novas 60 inch width. Prob why TV guys wanted to use cheaper doner car equipped with 12 bolt & narrow it to fit. At a glance one bolt dead centered on bottom of cover = 10 bolt, two level on bottom = 12 bolt. Easier than trying to lay in grass & count all the bolts. Crazy cool stuff . Truck HO33 Way heavier duty! Good luck!
     
    Last edited: Oct 22, 2014
    loudbang and Moonglow2 like this.
  17. No way..Urban legend or some other kind of street burner BS
     
  18. flux capacitor
    Joined: Sep 18, 2014
    Posts: 676

    flux capacitor
    Member

    Well at least for the COPO cars only. They have some strange but cool drivetrain upgrades.
     
    Last edited: Oct 22, 2014
  19. biscaynes
    Joined: Mar 16, 2008
    Posts: 1,649

    biscaynes
    Member

    'impala' 12 bolt is the same 8.875 diff as the other a/f/x body cars. 12 bolt 1/2ton truck diff is not the same sorry.
     
  20. flux capacitor
    Joined: Sep 18, 2014
    Posts: 676

    flux capacitor
    Member

    Whoops, my bad, I have once again learned something new today! The COPO cars were the only ones to have the truck "HO33" ring gear center chunk and the Impala 12 bolt is the same as the 8.875 car, just checked the old BCA bearing book for pinion bearing #'s and as biscaynes said the impala is same ring gear as others. Always good to know these things. TV guys prob used impala housing to same some money over aftermarket expensiveness. I revised the error of my ways. That's what I love about this place always something new to be learned. Sorry guys, thanks for the lesson!
     
    Last edited: Oct 22, 2014
  21. Back in early 81, I built a V8 Vega, and used a 67 Impala 12-bolt, narrowed and with "Olds" bearing ends to eliminate the c-clips. I put a Moroso Brute Strength limited slip in along with 4.10 gears and it all fit fine. It was the same Chevy style car 12-bolt as any other Chevy car 12-bolt. Only difference is i did not use the Chevy style c-clip axle retainers.
     
  22. Dealer packages and special run cars were almost never allowed in NHRA Stock classes...That would include 427 68 Chevy II's (not necessarily Novas) .
    Personally , I don't see the wisdom of building packages that weren't accepted by NHRA..Drag racing was a big deal back then.. Of course Fred Gibbs was in AHRA country.
    As an aside, truck rears weren't allowed in NHRA Stock and Super Stock unless factory installed. (Dana 60)
     
  23. models916
    Joined: Apr 19, 2012
    Posts: 380

    models916
    Member

    COPO cars were ordered by dealers, not just produced by Chevrolet as a whim. A dealer or dealers got together and decided what they wanted and got a quote from the production office and if accepted, the order was run.
     
  24. speedyb
    Joined: May 12, 2010
    Posts: 484

    speedyb
    Member
    from socal

    Interesting , all these years of scrounging 12 bolt parts and housing and I never thought of using a Impala housing or posi when I was younger. I'm going to measure the with of my 66's 12 bolt, I bet It's the same as an early chevelle
     
  25. Junior Stock
    Joined: Aug 24, 2004
    Posts: 1,822

    Junior Stock

    Not sure what year Impala housing I have, but it has bigger axle tubes than the one in my Nova.
     
  26. GRX
    Joined: Mar 28, 2014
    Posts: 68

    GRX
    Member
    from MD

    Yes. But like Justin said in post #10 the BOP were 10 bolt in a 12 bolt housing.
     
  27. Not in 1970 ..12 bolt cover , 12 bolt carrier..just like a Chevelle.
    Not urban legend or cruise night talk either, my friend.
    I parted out more than one 70 GTO.
     

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