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12 bolt questions *UPDATED*

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 90K5, Sep 12, 2001.

  1. 90K5

    90K5 1/2 ton status

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    Allright - I know of 2 12 bolts I can probably have, one for cheeap, and one for free.

    The free one is the best deal, its 6 lug, 3.73's, but the trucks its in might be sold, don't know right now If the truck isn't sold, I can probably swap it with mine for free.

    The other one is in a late 70's 2WD truck, so its 5 lug, and I don't know the ratio. What would be the standard ratio in it? Its 1/2 ton 2WD, don't know what engien it came with, but has a TH350. I could buy this whole truck for $300, so I could probably get the rear for about $100

    Are the spring pads and shock mounts the same on the 2WD and 4WD 12 bolts?

    Can I put the 30 spline axles from my 10 bolt in the 2WD 12 bolt? I know this truck has seen less abuse, and has had small tires all its life. The only thing I need to find out aobut it is the ratio, but I have a bad feeling its 3.08, and I need 3.73. Thanks

    90K5&lt;P ID="edit"&gt;&lt;FONT class="small"&gt;&lt;EM&gt;Edited by 90K5 on 09/12/01 04:50 PM.&lt;/EM&gt;&lt;/FONT&gt;&lt;/P&gt;<P ID="edit"><FONT class="small">Edited by 90K5 on 09/18/01 08:44 PM.</FONT></P>
     
  2. Executioner

    Executioner 1/2 ton status

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    Re: 12 bolt questions

    1. Standard ratio 3.07:1
    2. No 2WD 70's spring pad and shock mounts are not the same as 4WD spring pads and shock mount
    (your thinks about putting a 2WD 70's 12 Bolt into a 90's 4WD ????????? )
    3. No 90's 30 spline will not fit.
    Good luck
     
  3. 90K5

    90K5 1/2 ton status

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    Re: 12 bolt questions

    The guy didn't sell the truck, its just in the shop...I can probably convince him to trade rearends, and since he's selling the truck, he doesn't care if mine is bad. He already told me that...smart, huh?

    90K5
     
  4. 90K5

    90K5 1/2 ton status

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    Re: 12 bolt questions

    I'm going to need to make my rearend last a little longer, just a few more weeks if I can. This is kind of ghetto, but if I put some thick grease, like wheel bearing grease in with the gear oil, will that lube the bearings enough to make them last a little longer? Right now it sounds really bad, and smells like burning gear oil all around my truck. Don't know if that guy will take it anymore, but maybe I can make this live a little longer so I can find another one. Thanks

    90K5
     
  5. 1990K5

    1990K5 1/2 ton status

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    Re: 12 bolt questions

    no--- there are tapered bearings in the rearend, if you put grease in the diff you will blow it up in no time
     
  6. 90K5

    90K5 1/2 ton status

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    Re: 12 bolt questions

    what about putting 80w-140 in there? It starts making noice when it gets hot, so it seems like some heavier oil in there might help...?

    90K5
     
  7. Emmettology 101

    Emmettology 101 3/4 ton status

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    Re: 12 bolt questions

    What problems are you having? If it is "howling" under throttle, then it will last a while. My Dad always buys fullsize vans that have conversions and they come with 10 bolts. The last 3 have hollowed when under throttle and the recent one is pretty loud... But they are holding in there and he hasn't done anything about this one yet and it's been hollowing for about a year.

    Mike

    <font color=green>"My K5 is purdyr than your sister!"</font color=green>

    <a target="_blank" href=http://www.geocities.com/emmettology101>www.geocities.com/emmettology101</a>
     
  8. Executioner

    Executioner 1/2 ton status

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    Re: 12 bolt questions

    If you can find it try stairt 60W motor oil, or strait 140W gear oil.
    Keep your fingers crossed, I hope you don't have a heat problem in that 10 Bolt.
     
  9. 90K5

    90K5 1/2 ton status

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    Re: 12 bolt questions

    It started howling a little less than a week ago, and now when its been driven a while, it gets a lot worse, sounds like there is no gear oil at all.

    90K5
     
  10. Emmettology 101

    Emmettology 101 3/4 ton status

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    Re: 12 bolt questions

    Yep, that what my Dads van sounds like! Most shops are telling him he needs a new ring and pinion because his noise is only heard under throttle and not when completely off the throttle.

    Is this how yours is or does it make the noise constantly? Constantly would probably be bearings.

    Mike

    <font color=green>"My K5 is purdyr than your sister!"</font color=green>

    <a target="_blank" href=http://www.geocities.com/emmettology101>www.geocities.com/emmettology101</a>
     
  11. 90K5

    90K5 1/2 ton status

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    Re: 12 bolt questions

    When its howling, its only when I'm on the throttle, but when it gets hotter and the gears make a lot of noise, its almost constantly.

    90K5
     
  12. K5Jimmy

    K5Jimmy 1/2 ton status

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    Re: 12 bolt questions

    try the Stan Hopkins Company down on CF Hawn (if I remember right)....it's a family operation that has done several rearends for a friends dirt track car.....214-398-0696.....couple years ago I took them my gears and grabbers and an old 12B I had layin' around....they took my parts and put them in my 12B and 10B front.....I swapped them the low mileage 10B/3:08 in my truck and a couple hundred bucks, and drove out with 4:10's F/R, Auburn Pro F/R, and a 12B.....since 3:73 is such a common factory gear, I bet they could hook you up with a used quiet rearend for fairly cheap.....I'd just give 'em a call and see what they can tell you.....they did ok by me......JD

    Stuck?...Hell no..I still got some gas left..
     
  13. 90K5

    90K5 1/2 ton status

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    Re: 12 bolt questions

    I called them, but they aren't at that number anymore, I'll look them up though...I heard of another place called Drivetrain Warehouse near TI Boulevard, but couldn't find it either. anyone in the Dallas area know of a good 3.73 rear end I could buy, or another place that sells rears? Thanks

    90K5
     
  14. K5Jimmy

    K5Jimmy 1/2 ton status

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    Re: 12 bolt questions

    I'm guessing that you have already called all those Yards on Jefferson....you can use the 12B from a 2wd truck as long as it came with leaf springs.....all 12B are 30 spline, and stock new shafts are like $90....good luck..

    Stuck?...Hell no..I still got some gas left..
     
  15. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Re: 12 bolt questions

    Since he has a '90 I will assume it has a 10B &amp; he will need new drums as well if he goes the 2WD route.

    Jim '80 GMC & '73 Blazer
    Tread Lightly!
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  16. 90K5

    90K5 1/2 ton status

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    Re: 12 bolt questions

    Found an ad for Stan Hopkins Co...its 214-398-0636...thanks, going to call them tomorrow, hopefully can find something I can use there.

    90K5
     
  17. K5Jimmy

    K5Jimmy 1/2 ton status

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    Re: 12 bolt questions

    Musta pooshed the rwong button from whut I rote frum the Fone book........my bad.......good luck......

    Stuck?...Hell no..I still got some gas left..
     
  18. 90K5

    90K5 1/2 ton status

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    Re: 12 bolt questions

    Called them today, they want about $675 to fix my 10 bolt and put 3.73's in it, $740 for a 12 bolt with 3.73s open, and $1025 for one with a locker. That first 10 bolt I found is starting to sound a lot better. I can still get it for $100, it probably has 33.73's in it. going to pull the cover off tomorrow and take a look. The guy that took t out of the suburban said the Sub only had 64K on it, but I think an '84 rolls over ans starts over again at 100K...anyone know. If thats the case, and it probably is, it has 164K on it. I saw the Sub before he got rid of it, and it was a piece. But if it looks good, its only $100, I might jump on it. It has new brake shoes, and cylinders too...

    I took my 10 bolt out today, except for the parking brake cables...it was pretty easy, did notice I need to lower my transfer case again after the tranny rebuild though...I had thought I felt a little more vibration since that rebuild...

    90K5<P ID="edit"><FONT class="small">Edited by 90K5 on 09/17/01 07:42 PM.</FONT></P>
     
  19. Hossbaby50

    Hossbaby50 3/4 ton status

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    Re: 12 bolt questions

    My 85 Jimmy rollled back to zero at 100K. Your probably right in thinking that there is 164K on it.
     
  20. 90K5

    90K5 1/2 ton status

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    I think I'm going to go ahead and get the 12 bolt built for $740, with open diff, and 4.11's. I'll probably keep this truck for a while, and need something that will last. Do ya'll think a 12 bolt rebuilt well will last a long time with 33's hardly ever driven off-road?

    90K5
     

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