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12 bolt rear

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Oblin Goblin, Jun 8, 2000.

  1. Oblin Goblin

    Oblin Goblin 1/2 ton status

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    My rear end is going out and it looks like the most cost effective fix will be to get a housing with gears from a local junk yard. I'm thinking about going to somting stronger like a 12 bolt as long as i'm replacing the rear axel. The problem is that I'd have to get axel shafts for the new axel instead of using the ones I have now, an extra $200. Would it still be woth while to upgrade to the 12 bolt if I can find one? I plan on turbocharging my 6.2 Diesel and getting some 33" tires so I might need a stronger axel but my main concern is carrying capacity. Givin that the rear axel is already supporting 2600 lbs it seems like it will be pretty easy to go aver the axels 3550 rating with just a trailer and some stuff in the back. How well do 10 bolts hold up to being over loaded? Are 10 bolts made after a certain year stronger than others?

    Also, how hard to find are semi floating 14 bolts? If I find one will I be able to use my stock brakes and wheels?
     
  2. bablazer73

    bablazer73 1/2 ton status

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    I guess my answer would depend on what part of you rear axel is going out! 10 bolts are easy to get parts for, and aren't hard to rebuild. 14 bolts are fairly common. 2 and 4 wheel drive are the same, but you will have to deal with 8 lug wheels on the rear. converting the front to match can cost some. 14 bolts are stronger, but larger. cutting down ground clearance. and alot heavier. 12 bolts are ok, but have broken them under hard usage. I personally like the 10 bolt axel, I used 1 for many years in a nitrous feed 400 sb camaro I drag raced. 4 years worth! 2 engines, 2 trannys, never blew the rear! as far as stronger? in the late 80's, around '88, gm changed axel splines, which made the axels stronger, but switched posi units to a gov-loc. which was weaker! haven't figured that out yet! I have both 10. bolts and 12 bolts layin around. but have used all my 14 bolts. do you need parts? or a whole axel?

    your right. I don't understand the jeep thing!
     
  3. ken

    ken 1/2 ton status

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    Your best bet would be to find a semi-floating 14 bolt from an '88 and up light duty 3/4 ton truck. These will have 6 lugs, 9.5" ring gear, and 33 spline shafts. I picked one up a while back for $150. Your other alternative is to find a 12 bolt, which stopped being installed in 1/2T GM trucks in 1981. Don't waste your money on a 10 bolt, they are TOTALLY WORTHLESS. If you do listen to everyone here and spend money on it, YOU WILL REGRET IT, as it will blow up again, THERE IS ABSOLUTELY NO DOUBT ABOUT THAT!!!!

    ken
     
  4. BIGJ

    BIGJ 1/2 ton status Author

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    Hey oblin. I have a 12 bolt that I need to get rid of. It has 4.56 gears and a detroit. All parts are less than 2 years old (except the housing). Let me know if you are interested. I live in Little Rock Arkansas.

    BIGJ
     
  5. Oblin Goblin

    Oblin Goblin 1/2 ton status

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    Thanks for the reply's. I just had another shop look at my truck and he said there was a good chance I'd need new axel shafts, so maybe thats a moot point. I'll try to find a semi-floating 14 bolt around here. Will it be a simple bolt up to swap one in? Can I use my existing rear brakes and wheels? How much more does a 14 bolt weigh and how much ground clearance will I lose? Were there many 14 bolts with 3.42 rears? The 12 bolt that BIGJ has sounds nice but I'd like to stay with 3.42 gears for now so I don't have to change anything in the front.
     
  6. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Hey BigJ, how bad do you want to get rid of it? I might be intrested. Jim.

    BigJBear '80 GMC
     
  7. 6.2Blazer

    6.2Blazer 1/2 ton status

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    Might as well bring this up again........10-bolts are not totally worthless. The "built" 10-bolt in my Blazer has survived a torquey diesel engine and 35" tires on tough trails with no problems as of yet (knock on wood.....). To give you an idea of how it's used, I've broken 2 front axle u-joints in the last 3 months on the trail.
     
  8. ken

    ken 1/2 ton status

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    That's cuz you got so much weight up front cuz of the diesel engine!!

    ken
     
  9. 6.2Blazer

    6.2Blazer 1/2 ton status

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    I'm sure it doesn't help matters any, but add a winch and heavy bumper onto the front of a gas powered rig and it's about the same.
    The worst part is that the u-joints breaking also took out the yokes on the shafts and front 30 spline 10-bolt axles are virtually non-existent in junkyards or as factory replacements.................oh well, it was a perfect excuse to order chromoly axles and fusible clutch rings from ORD!!!!!!
     
  10. ken

    ken 1/2 ton status

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    And I bet what you've spent on stock axleshafts, u joints, chromoly shafts, and fusible clutch rings, you couldda bought a Dana 60 and never broke again!! Food for thought!!



    ken
     
  11. Depdog

    Depdog 1/2 ton status Author

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    Well, I have a 12 bolt and have not broken anything, and before you say its not wheeled, you might want to ask around. I dont treat it kindly and it holds up just fine, my Beast weighs around 6500 lbs loaded for the trail. If you want to drag that dana 60 or 14 bolt all over the rocks come on down to Tellico and I will be happy to get you un- high centered.

    Just pokin at ya. The D-60 and 14 bolt full floater are both great axles, but I dont have the time or money to swap all the stuff involved and then change the front end for 8 lug wheels. If you mean the semi float dana 60, to get 6 lug axle shafts made, why bother, the shafts are what breaks on a 12 bolt and you can get new stronger ones and not worry about it.

    Depdog

    <font color=blue>"Lead, Follow, or BECOME the Trail"</font color=blue>
     
  12. 6.2Blazer

    6.2Blazer 1/2 ton status

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    It's going to cost under $600 to upgrade the 10-bolt. The chromoly's are going to replace the original axleshafts which are now hashed (the only other option was shafts through the dealer for not much less). This is well under what it would cost to swap in a Dana 60 (they are really expensive around here and the condition of junkyard parts is always questionable), install a locker or limited slip in it, and buy new rims and tires............gee, I could have just spent an extra grand or two and had the 60, don't know what I was thinking!!!!! That grand will pay for a whole lot of $12 clutchrings and the 15 minutes to replace them.
     
  13. ken

    ken 1/2 ton status

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    I guess I'm crazy then. All 3 of my 60 fronts were had by buying complete one ton K30 trucks for $1450, $1500 and $1200, and parting them out. The 60s ended up costing me zero. Two of the trucks were military CUCVs which means they had 4.56 gears, Detroit rear, and Trac-Lok front. 60s for free...Oh well, life is sometimes good!!!

    ken
     
  14. AZK5

    AZK5 1/2 ton status

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    What the h*ll is a clutch ring?
    CB
     
  15. ken

    ken 1/2 ton status

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    A clutch ring is a f"fusible link" of sorts, allowing an easily replaced, cheap part that is engineered to break before anything more expensive breaks, like u joints, asle shafts, etc. It is part of the locking hub. I still think a front Dana 60 is cheaper in the long run. [​IMG]

    ken
     

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