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12 bolt swap worth it?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 84k5, Mar 11, 2001.

  1. 84k5

    84k5 1/2 ton status

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    Is it worth it to swap from a 10 bolt to a 12 bolt? I know all the dimensions of both axles, but I'm not sure if the slight increase in size is worth a swap. Either way I want to get Moser shafts and a Detroit. I read in a Four Wheeler article a while back that the pinion on a 10 bolt is bigger than on a 12 bolt. Is this true or a typo? As far as usage the k5 has 33s, is a daily driver, never tows anything, but takes some abuse out in the desert. I'm planning on some 4.56 gears either way too. Thanks for the input.

    Brian
    <A target="_blank" HREF=http://84k5.coloradok5.com>http://84k5.coloradok5.com</A>
     
  2. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    if you are not rock crawling i would say yes it is worth it. if you are i would say go 4 a 14bolt

    s.smith 77blazer lookin 4 mud [​IMG]
     
  3. CaptCrunch

    CaptCrunch 1/2 ton status

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    For your application... maybe. I just picked up a 12b and dana 44 to swap in my 87[​IMG]. Just make sure the 12b isn't a gov-lock...yuck! Either way a 12b w/ Moser axles, those Green bearings they have that are double-wide, studs or a cap upgrade inside and it should be pretty stout. BTW... 12b is a 8.75 while 10b is a 8.5 pinion. Also not sure I'd really want 4.56's on the street w/ 33's... 4.56's are also pushing a 12b, but since you do sand mostly I think you'lll be ok.

    1987 Chevy K5 Blazer- 350 TBI
     
  4. 84k5

    84k5 1/2 ton status

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    Actually 8.75 and 8.5 are the size of the ring, not the pinion. The 14 seems like too much with 33" tires. More opinions welcome.

    Brian
    <A target="_blank" HREF=http://84k5.coloradok5.com>http://84k5.coloradok5.com</A>
     
  5. Jason73K5

    Jason73K5 1/2 ton status

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    I wouldn't think you'd get enough of an increase in strength, if any to justify the swap. I personally have had more problems with dana 44's and 12 bolts than I have with 10 bolts front or rear.
     
  6. Sammy

    Sammy 1/2 ton status

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    I'm planning on using a 12b for 35"s and 4.56. Is that going to work?

    "K5 Grand GT Silverado in the Netherlands."
     
  7. 85m1009

    85m1009 1/2 ton status

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    I,ve been using the same 12 bolt with 4.88's, detroit locker, moser axles, green bearings, with 36's for over four years. It started out under my suburban that has been all over the country four wheeling. The sub weighed close to 9000 lbs. with all my gear and family. I've had the same rear end in my Blazer for over a year and have wheeled the heck out of it. I believe the way any rear end survives is good maintenance and knowing when to stay off the skinny pedal if you have a lot of horsepower. Just my two cents.

    <font color=yellow>Steve Frisbie</font color=yellow>
     
  8. Emmettology 101

    Emmettology 101 3/4 ton status

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    Actually the 12 bolt is an 8.875 ring gear.

    Mike [​IMG]
    See <font color=green>EMMETT</font color=green> -&gt; <A target="_blank" HREF=http://emmett.coloradok5.com>http://emmett.coloradok5.com</A>
     
  9. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    If it doesn't cost you too much, go with the 12 bolt. It's a bit larger in about every important area, so why not?

    Making the world better, one truck at a time.
    [​IMG]
    SW-ORD
     
  10. CaptCrunch

    CaptCrunch 1/2 ton status

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    Hey steve...
    Moser sells those Green bearings don't they? Have read about them, but didn't see them listed on Moser's website. Thanks


    1987 Chevy K5 Blazer- 350 TBI
     
  11. 84k5

    84k5 1/2 ton status

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    12 bolt it is. Next decision is the warn kit or Moser shafts and wether or not 4.56 is too low with 33s. I have OD, so I think it shouldn't be a problem. Any comments on either of these decisions? Who makes the stronger caps mentioned above?

    Brian
    <A target="_blank" HREF=http://84k5.coloradok5.com>http://84k5.coloradok5.com</A>
     
  12. CaptCrunch

    CaptCrunch 1/2 ton status

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    Mark Williams makes the cap I was reffering to... sounds good, bur requires milling to to fit it... here is the link <A target="_blank" HREF=http://emporium.markwilliams.com/prodinfo.asp?prodid=1929>http://emporium.markwilliams.com/prodinfo.asp?prodid=1929</A> Also Drivetrain direct sells something similar I believe for more like $80 or $90. I have never actually seen a cap break... although I suppose they could... but decided to get a set of ARP studs for the caps at the cost of $24[​IMG], should be good enough for my purposes. I'm going the Moser shafts and green bearings that Steve was speaking of... sounds like an excellent combo and quite a bit cheaper then the FF kit, but if you want to be as close to bullet-proof as you can get with a 12B it is the way to go IMO... Our good bud Stephan @ ORD sells them[​IMG] so you can check them out on their site. Gears... well if you are going on the street I'd say 4.10's would be good. Since you have a 700R4 keep in mind you have a much lower first gear then a TH350 or TH400 so would still be excellent offroad... I'm going 4.10's w/ 35's
    1987 Chevy K5 Blazer- 350 TBI<P ID="edit"><FONT SIZE=-1>Edited by CaptCrunch on 03/12/01 08:17 PM (server time).</FONT></P>
     
  13. jcg

    jcg 1/2 ton status

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    I just had a 12b swapped in last month with a lockright and 4.56's and I'm running 33's right now. It's a little overgeared but the OD more than makes up for it on the highway. Dusting kids in their daddy's sportscars is fun too! [​IMG] I put the low gears in because I'm going to 35's for my next tires, maybe 37's if I can afford to upgrade the shafts at the same time. Crawling around in 1st gear and 4low is increadible, the truck just walks over everything (I have a truetrac in the front too). I'd say that if your not into serious crawling and your going to stay with the 33's for a while, go with the 4.10's. You'll probably be a little happier with it on the road and it won't empty your gas tank quite as fast.

    Joe
    RIT Mini-Baja http://www.rit.edu/~bajawww
    Team Mudnuts http://www.mudnuts.org
     
  14. jcg

    jcg 1/2 ton status

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    Almost forgot...
    If your having a shop do the swap for you, see if they will put the 10b yoke and stuff on the 12b for you (and hopefully not charge you anything more). My shop did it just because my rear u-joint was brand new and they didn't feel like changing it over to a conversion joint. The 10b pinion stuff is stronger than the 12b. Why?... I haven't got a clue. They put those green bearings in too, I think they got them from Autozone.

    Joe
    RIT Mini-Baja http://www.rit.edu/~bajawww
    Team Mudnuts http://www.mudnuts.org
     
  15. BillyBob

    BillyBob 1/2 ton status

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    Well, I've had my truck a little over a year now. I've never wheeled it hard or anything like that... yet.... but I feel a lot safer with the 12B rear under it. Although people don't say it's worth it, I think it really is. It's gone over some pretty nasty rocky and hilly terrain and is still in one peice.. something I don't think a 10 bolt could do. Anyway, as to your choice of gearing, 4.56s w/ 33s is a little too low. I've got 3.73s in mine w/ 33's and it's pretty good. I feel it's a little undergeared.. 4.10s are next. However, the 4.10s come in a 14B FF ![​IMG] 3/4 ton for me!

    <A target="_blank" HREF=http://billybob.coloradok5.com>http://billybob.coloradok5.com</A>
    If it ain't leaking oil, it ain't my truck![​IMG]
     

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