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30 spline 10bolt stronger than 28 spline?

Discussion in 'The Garage' started by jjlaughner, Jun 19, 2004.

  1. jjlaughner

    jjlaughner 3/4 ton status

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    /forums/images/graemlins/dunno.gif

    Talkin about the front axle!
     
  2. krayzie

    krayzie Registered Member

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    28 spline rear diffs are from 2WD pickups. The 4x4's are the ones equipped with the 30 splines. 30 spline carriers are beefy compared to the 28's, well.. at least as beefy as a 10 bolt can be /forums/images/graemlins/1zhelp.gif
     
  3. jjlaughner

    jjlaughner 3/4 ton status

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    I mean front diff 10bolts... 28 spline before 88, 30 spline after....

    I'm wondering if there's no neck down at the slines or what the deal is?

    Pics anyone
     
  4. 88Silverado

    88Silverado 1/2 ton status

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    I know the rear axles taper down the same on the rears so there really no axle strength improvement. I dont know about the front /forums/images/graemlins/dunno.gif My 88 is 28
     
  5. Big Red

    Big Red 1/2 ton status

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    <font color="red"> both of my axles (F&amp;R) are both 28spline. its kinda a luck of the draw. i dunno, 2 more spline dun seem to me (and my logic may be fuked up) much stronger. but they are. though i do believe its marginal. </font>
     
  6. HarryH3

    HarryH3 1 ton status Author

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    Since the diffs are interchangeable front to rear, my guess is that someone at GM figured out that they would need to stock one less part if they used a 30-spline diff up front, so it would be the same one they were using out back. /forums/images/graemlins/shocked.gif
     
  7. jjlaughner

    jjlaughner 3/4 ton status

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    [ QUOTE ]
    I know the rear axles taper down the same on the rears so there really no axle strength improvement. I dont know about the front /forums/images/graemlins/dunno.gif My 88 is 28

    [/ QUOTE ]

    ok so 89 up is 30 spline and the axle shafts are the same sizes just different splines?
     
  8. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    [ QUOTE ]
    ok so 89 up is 30 spline and the axle shafts are the same sizes just different splines?



    [/ QUOTE ]

    Outside of a little carryover until run out of 28 spline, this is correct. 2wd or 4wd, front or rear, 28 spline to 89, 30 spline from 89. Marginally stronger, harder to find. Those years trucks are either wrecked, still running, or owned by a wheeler and sport 14bff by now /forums/images/graemlins/k5.gif
     
  9. 88Silverado

    88Silverado 1/2 ton status

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    I believe the rear 30 spline shafts are slightly larger diameter but they taper down to the same diameter just after the splines so that becomes the weak point on both axles.
     
  10. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    got this from the specs page
    [ QUOTE ]
    1988, GM Corporate 10-bolt (8.5-in. 1.28 Axle Dia. 28 Spline)


    [/ QUOTE ]
    [ QUOTE ]
    1989, GM Corporate 10-bolt (8.5-in. 1.28 Axle Dia. 30 Spline)


    [/ QUOTE ]

    i would stay with the 28 spline, if you break and 30 spline inner, its harder to find the correct axle.
     
  11. Jonny-K5

    Jonny-K5 1/2 ton status

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    i've got 30 spline f/r on my 10b. truck is an 89. it is harder to find used parts in 30 spline, but anywhere that you can buy a new 28 spline shaft you can get a 30 spline.

    what i did what swap out the stock shafts for moser alloy shafts. for about 20bucks more per shaft you get stronger steel and no necking down.
     
  12. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I'd say both are equally worthless. I ran 28 spline when I ran a front 10 bolt becaus as said above, easier to get parts for.

    Swapped my last set of spare shafts into the axle and removed it from the rig. /forums/images/graemlins/rotfl.gif /forums/images/graemlins/thumb.gif
     
  13. heavy4x4

    heavy4x4 1/2 ton status

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    I've got front and rear 30 spline 10 bolts for sale. /forums/images/graemlins/deal.gif /forums/images/graemlins/wink.gif
     
  14. 6.2Blazer

    6.2Blazer 1/2 ton status

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    The 28-spline shafts are 1.28" in diameter, the 30-spline shafts are 1.31" in diameter.

    I had 30-spline 10-bolts both front and rear in my '90 K5. The rear shafts had no apparent neck-down in them and therefore should be approximately 20% stronger than the 28-spline versions, and even more if you upgrade to aftermarket high strength rear shafts.

    The front inner 30-spline shafts have a necked down area just like the 28-spline shafts...but I'm not sure if the neck down is as small on both styles or not. In any case you probably won't gain that much strength on the front by using factory 30-spline shafts. Again, aftermarket shafts in the front without a neck-down area would provide a good strength increase but nobody that I know of currently makes a 30-spline 10-bolt inner front shaft in chromoly without doing something custom.

    The factory 30-spline carriers are known to be a little weaker than the 28-spline versions because they simply milled out the ends of the carrier to accept the larger shafts. An aftermarket carrier shouldn't have this problem though.
     
  15. gzzgfw

    gzzgfw 1/2 ton status

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    [ QUOTE ]
    I'd say both are equally worthless.

    [/ QUOTE ]
    /forums/images/graemlins/histerical.gif /forums/images/graemlins/histerical.gif /forums/images/graemlins/histerical.gif
    Now that's coming from a 60'd guy!

    Strength is a direct factor of how big the 2x4 block is under the skinny pedal! /forums/images/graemlins/thumb.gif
     
  16. HarryH3

    HarryH3 1 ton status Author

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    [ QUOTE ]
    The factory 30-spline carriers are known to be a little weaker than the 28-spline versions because they simply milled out the ends of the carrier to accept the larger shafts. An aftermarket carrier shouldn't have this problem though.

    [/ QUOTE ]
    I don't follow the logic here. The inner diameter is determined by the axle size, while the outer diameter is limited by the inner race of the carrier bearing. So an aftermarket carrier should have the same weakness.
     
  17. 88Silverado

    88Silverado 1/2 ton status

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    Where the axles slide thru the carrier and the C-clips attached is a larger hole so the 30 spline can slide thru, thus making the carrier weaker
     
  18. HarryH3

    HarryH3 1 ton status Author

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    [ QUOTE ]
    Where the axles slide thru the carrier and the C-clips attached is a larger hole so the 30 spline can slide thru, thus making the carrier weaker

    [/ QUOTE ]
    That part I understand. /forums/images/graemlins/wink.gif But wouldn't an aftermarket carrier for a 30 spline have to be made with the same "too thin" parts? I don't see how it could be made any differently.
     
  19. 6.2Blazer

    6.2Blazer 1/2 ton status

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    [ QUOTE ]
    [ QUOTE ]
    The factory 30-spline carriers are known to be a little weaker than the 28-spline versions because they simply milled out the ends of the carrier to accept the larger shafts. An aftermarket carrier shouldn't have this problem though.

    [/ QUOTE ]
    I don't follow the logic here. The inner diameter is determined by the axle size, while the outer diameter is limited by the inner race of the carrier bearing. So an aftermarket carrier should have the same weakness.

    [/ QUOTE ]

    I don't know the specifics, but the stock carrier was designed for the smaller shafts and then bored out while aftermarket carriers are designed from the start for the 30-spline shafts. Your assumption is that the weak spot of the stock carrier is at the diameter of the carrier bearing surface. The Eaton Posi (not a Gov-lock) that I installed in my front 30-spline 10-bolt used different carrier bearings than the stock carrier.

    There's also more to the strength of a part than just physical size.....
     
  20. 88Silverado

    88Silverado 1/2 ton status

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    [ QUOTE ]
    aftermarket carriers are designed from the start for the 30-spline shafts.

    [/ QUOTE ]

    Thats why I threw an Eaton Posi in my rear with 28 spline and a Auburn in the front. Well...that and they were free /forums/images/graemlins/thumb.gif
     

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