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12 bolt vs. 14 bolt

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BlazerGuy, Jun 11, 2000.

  1. BlazerGuy

    BlazerGuy 3/4 ton status

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    Can a 12 bolt be almost as strong as a 14 bolt? I know they can't be exactly the same in strength, but I want something strong but not as hefty as a 14 bolt. I know Warn makes a full-floater kit for the 12 bolt. Thanks guys.

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  2. ken

    ken 1/2 ton status

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    I would say a 14 bolt is at least twice as strong as a 12 bolt. Even with alloy high strength axles in the 12, the housing is just not as strong as the 14. Oh, and then there's the lovely c-clip method of axle retention in the 12 bolt = BREAKAGE!! If you're running under 35" tires, the 12 should be enough.

    ken
     
  3. 6.2Blazer

    6.2Blazer 1/2 ton status

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    There is really no reason why the c-clip design would cause more breakage. The only real disadvantage a c-clip axle has is that if an axle does break, there is nothing to keep the tire and wheel attached to the vehicle. If you look at the design of a c-clip axle shaft, there is really no stress put on the machined c-clip groove as all of the stress is between the splines in the differential and the tire. There is some side loading force applied to the c-clip, but this design is actually much stronger in side loading conditions than just having a pressed on bearing holding it in. BTW, I have seen a couple of flanged Dana 44's (a.k.a. - non c-clip design) chuck the tire and wheel off the vehicle while driving down the road.......
    Anyway, the full floating 14 bolt is much stronger than a 12-bolt, but the 12-bolt will hold up to a lot, especially with Warns kit installed. Check out Off-Road Designs website (www.offroaddesign.com), the owner recently replaced a full floating 14 bolt with a 12-bolt and Warn full floating kit (yes, he removed the 14 and replaced it with a 12) in his Blazer which runs a built 383 and 37" tires and is used to rock crawl out west.
     
  4. BlazerGuy

    BlazerGuy 3/4 ton status

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    Yeah, I'm probably going to just run 33's and maybe 35's so I think it will hold up. Doesn't the Warn kit eliminate to c-clip? Thanks for the advice.

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  5. 6.2Blazer

    6.2Blazer 1/2 ton status

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    Yes, the Warn kit eliminates the c-clips.
     
  6. HarryH3

    HarryH3 1 ton status Author

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    14-bolt FF's are Very beefy. Drum to drum they weigh around 525 lbs. (Converting to rear discs supposedly reduces total weight by about 75 lbs.) A 12-bolt weighs closer to 300 lbs. There is a lot of steel in a 14-bolt!

    The ring gear diameter on a 12-bolt is around 8.5 inches. On the 14-bolt FF it's 10.5 inches.

    The carrier on a 12-bolt has a single cross shaft, with 2 spider gears. The carrier on a 14-bolt F has an "X" shaped shaft with 4 spider gears (on an open diff). A Detroit Locker for the 14-bolt FF uses all 4 drive points as well.

    The pinion shaft on a 12-bolt is supported by two tapered bearings. The pinion shaft on a 14-bolt FF is supported by two tapered bearings and a roller bearing at the end of the shaft (similar to a 9-bolt Ford). This keeps the pinion gear from flexing under load.

    The 14-bolt is way stronger, but a properly built 12-bolt will hold up fine for most people. I switched mine over to a 14-bolt in 1987, long before you could buy all the goodies to make a 12-bolt hold up better. I was tired of buying parts for 12-bolts so I traded up. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
    http://ThunderTruck.ColoradoK5.com
     
  7. Shawn

    Shawn 1/2 ton status Premium Member Author

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    You sure know your axles Harry! I felt like I just went through Axles 101...

    After the EJS trip I had a chance to talk to Steve Watson at Offroad Design and I remember him saying that he bent the 12 bolt a little. A truss may have helped prevent that.

    Shawn
    87 K5
     
  8. Jeff427

    Jeff427 1/2 ton status

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    I've heard that the twelve bolt axle tubes are prone to bending with severe usage unless they are trussed. I talked to a guy that races a K5 in Tough Truck competitions with a big block and a twelve bolt with a truss and hasn't had any trouble with it after racing it for several years.

    Jeff427
    http://jeff427.coloradok5.com/
    <font color=red>Mud Dog Off Road Club</font color=red>
     
  9. ken

    ken 1/2 ton status

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    Well, to be exact, a 12 bolt ring gear is 8.875". The shafts on a 14 bolt FF are 1 9/16"...yeah they're advertised at 1 1/2", but measure em!!! I think the 12 bolts come in at 1 5/16".

    ken
     
  10. '73 K5

    '73 K5 1/2 ton status

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    I beefed my 12 bolt without spending the huge amount of cash for the full floating kit. Moser axle shafts, ARP studs, US Gear ring and pinion gears, Eaton limited slip, ARP stud kit for the main bearing caps, T/A performance diff cover. AND I'm thinking about adding a truss.

    '73 K5
    Chevy good...Ford bad
     
  11. Not to retard this great conversation, but what is a truss (and what will it do for the 12)?
     
  12. Emmettology 101

    Emmettology 101 3/4 ton status

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    Has anyone spoke with Stephan from ORD about why he swapped his 14FF out in favor of the 12 boltFF? II may give him a hallor and find out. Also, I wonder how long they have had it in? I guess a long term test would show the results best!

    Mike
    1982 GMC Jimmy - Emmett
    http://emmett.coloradok5.com
     
  13. Kyle89K5

    Kyle89K5 1/2 ton status

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    Stephen changed his cause he was tired of the loss of ground clearence. That, and the full float kit helps beef his 12.

    Kyle
    89K5
     
  14. HarryH3

    HarryH3 1 ton status Author

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    Hi Shawn, the knowledge was hard earned... I've ripped teeth off of the ring gear in several 12-bolts.[​IMG]

    I haven't busted a 14-bolt. Yet.[​IMG]

    The only downsides to the 14-bolt are:
    It's heavy
    You lose some ground clearance.
    You have to change to 8-lug wheels.

    <font color=black>HarryH3 - '75 K5</font color=black>
    http://ThunderTruck.ColoradoK5.com
     
  15. BlazerGuy

    BlazerGuy 3/4 ton status

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    How much ground clearance does the truss take up. This is the main reason I didn't want to go with a 14 bolt because of the clearance and if the truss takes up a lot then I just should go with a 14. Thanks

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  16. Jeff427

    Jeff427 1/2 ton status

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