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woould like to clear this up once and for all....

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Jersey, Aug 24, 2001.

  1. Jersey

    Jersey 1/2 ton status

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    my rear 10 bolt is shot. i'm goin' to a bone yard tomm. to look for a "new" rear. I want to get a 12 bolt/6 lug, 3.42 to replace it for three reasons - strenth, same ratio as my front and width. I want the front and rear track to be even instead of using spacers. can someone tell me what to look for? what model and year trucks, vans, 4x4's? if there's a 12 bolt out there that will bolt up without changing spring perches and/or shock mounts and the 3" wider stance, that much better and easier, but not neccessary. Are there 12 bolts i should stay away from? gov locks, posi, LS's? Thanks.

    - Jersey

    '91K5 - 350, 700R4, NP241
     
  2. Chris Demartini

    Chris Demartini 1/2 ton status

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    <font color=blue>The only 12 bolts that will bolt in are narrower than your front axle. The van ones are wider than the truck ones but you need to re weld the spring pads and shock tabs. What yard is this? I have a 3.42 12 bolt from an 81 thats taking up space, I live in Dumont. It's about 30 minutes away from Wayne, I was just out there before. Send a PM if your interested.</font color=blue>
     
  3. Executioner

    Executioner 1/2 ton status

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    I don't think you will have much luck in your search with those parameters !
    Correct me if I am wrong but 12 bolts are usually 3.07/3.08/3.73/4.09/4.10/4.11,
    3.42 is rare.
    Also the wider axles from vans will need the spring perchs relocated, along with the scock mounts.
    Good luck, and I think you will need it.
     
  4. Jersey

    Jersey 1/2 ton status

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    Re: would like to clear this up once and for all....

    in the post before you, biggray says he has one so i was guessing that the 12 bolt '82 and before came with 3.42's? now i'm totally confused. Somehow, somewhere, someone has had to have done this and know exectly what's involved. hope this person reads this and posts a reply 'cause i'd like to get to a bone yard in the a.m. and look for....whatever the hell it is i'm looking for. I'm going to hate myself if i just wind up going with another 10 bolt, just because i know it'll work. I don't care about the perches or shock mounts, they can be welded in ten minutes. i just wanted to know what to look for. thanks for the replies..and thanks for the luck.

    '91K5 - 350, 700R4, NP241
     
  5. OneLeft

    OneLeft 1/2 ton status

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    It only took me 8 1/2ton rear axles (1 complete rebuild and 8 ring/pinions and 3 gov locks) to realize I should have gone with the 14bff w/detroit locker from the start.
     
  6. flblazer

    flblazer 1/2 ton status

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    i just got a 83 or 81 blazer that had 3:42s in it now i am putin them in my 84 i had 307 back 273 frnt i was sick of the gears thank god my friend found my a hole blazer 4 parts for 150 bucks heheheheheheheh the 342s kick ass in the mud now i need to put my bupers on now i got a ticket 50 buck for no bumpers well later hope you find some now i am sellin the 273s

    can some 1 find me a ford i need to take a pee still peein on that ford just have to keep goin dam i can not stop pissin:) k5s kings
     
  7. RedDwarf

    RedDwarf 1/2 ton status

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    There is no such thing as a 3.42 geared 12 bolt.

    The ratio was actually 3.40 for the 12 bolt truck

    I have one with the Gov Loc. I will rip out the guts if you want them. Cost you 100 bucks plus shipping.

    Lift It, Lock It, LIVE IT!!!
     
  8. Jersey

    Jersey 1/2 ton status

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    Thanks Red. So i guess droppin' a 12 bolt in, leaving my front 3.42 up front for now wont work if i want 4wd and not dropping gears into one of them. Do you know if the 14 bolt came with 3.42's? Possibly do the 14ff and a 6 to 8 lug conversersion up front.

    - Jersey

    '91K5 - 350, 700R4, NP241
     
  9. Triaged

    Triaged 1/2 ton status

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    3.40 rear would work fine with a 3.42 front. You are allowed a 1% difference before you will start to notice it (alot if trucks are off that much from the factory). If you are able to find a 3.4? from a van you would have to get custom axle shafts because vans are 5 lug.

    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
    <a target="_blank" href=http://community.webshots.com/user/triaged>See it Here </a>
     
  10. RedDwarf

    RedDwarf 1/2 ton status

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    Yeah, the 3.42 front/3.40 rear combo came from the factory.

    The big 14 bolt doesn't come with 3.42 gears (3.73 is lowest) but the SF 9.5" is common in 3.42 ratio.

    Lift It, Lock It, LIVE IT!!!
     
  11. Jersey

    Jersey 1/2 ton status

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    ok. so a 12 bolt 3.4(?) will work with my 3.42 front 10bolt. but they never can in a 6 lug in any pre-'82 vans? So everyone that's using these van 12bolts for the even tracking converts it from 5 lug to 6 lug? or no one is using these? just trying to figure it all out. Thanks.

    - Jersey

    '91K5 - 350, 700R4, NP241
     

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