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How rare is a 30 spline front 10 bolt?

Discussion in 'The Garage' started by 89GMCSuburban, Apr 21, 2002.

  1. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    I counted my splines and it turns out I have a 30 spline front 10 bolt. When compared to a 28 spline shaft, it is ever so slightly thicker and the neck down is a little larger. Pretty cool.
     
  2. Hossbaby50

    Hossbaby50 3/4 ton status

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    The 89-91 10 bolt front axles are 30 spline. The axles are stronger by a little, but I hate to break it to you, the 30 spline carrier is weaker then the 28 spline carrier.
     
  3. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    !!!!! Are you serious?? Why? That doesn't sound cool...
     
  4. Hossbaby50

    Hossbaby50 3/4 ton status

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    100% Serious. I don't remember exactly why, but they are. I doubt you could break the carrier unless you jumped it though. An axle u-joint or shaft will most likely go first. I have also heard that the lower the gear ratio, the more likely you will break a pinion too because the pinions get smaller with the lower ratios, but with 4.10 I don't think you will have to worry much.

    If you ever decide to run the chromo front axle shafts you might want to add a locker or LS at the same time that replaces the carrier so you don't have to worry about breaking it.
     
  5. Hossbaby50

    Hossbaby50 3/4 ton status

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    If you still have a 30 spline 10 bolt rear, that is the one I would be worried about more then the front. All though with the 31" tires you have I am not sure this is a huge problem. If you plan on large tires with the 10 bolts you have, you might consider a locker or LS that replaces the carrier in the rear.
     
  6. 6.2Blazer

    6.2Blazer 1/2 ton status

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    The front 30-spline 10-bolts were only found on '89-'91 K5 Blazers and Suburbans so they are fairly scarce. Fortunately, there are not that many different parts between a 30-spline and 28-spline front 10-bolts. The inner axle shafts are the main difference along with the carrier (differential) side gears. In order to make the larger 30-spline shafts fit they basically took a 28-spline carrier and machined out the axle bore, which on paper would make the stock 30-spline carrier slightly weaker but I wouldn't worry too much about it.

    The inner axle shafts are the hardest parts to find, they are out there but you just have to look a little harder (I've bought 3 complete sets off of this board in the last 2 years). The outer stub shafts and u-joints are the same as the 28-spline 10-bolts or Dana 44 fronts. Also to the best of my knowledge nobody is making an aftermarket alloy shaft though you can have some custom made for even more $$$.

    The carrier/differentials are no problem to get since they interchange with the rear 10-bolts and they are very common (GM used the rear 30-spline 10-bolt from about '88 to present) and there are also tons of aftermarket diffs available in 30-spline.
     
  7. user

    user Registered Member

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    How confident are you in that info?

    I'm in the process of rebuilding the front & rear diff's and I haven't pulled the front axles yet to count splines. The guy I'm ordering the new carrier from (drivetrain.com) isn't sure whether it's a 28 or 30 spline axle, so I'm being held up on the order until I get those splines counted. The truck is a 1990 GMC Suburban, 5.7L, auto trans/OD, 4wd w/10-bolts front and rear; towing package etc.

    Here's another question: anyone know the RPO/Service Parts code for the front diff that might enlighten one as to the number of splines on the axle shafts?

    (I don't actually do towing, and the truck is "all torque and no action", so I'm changing the ratio to 3.08 and adding Eaton Detroit Truetrac posi's.)
     
  8. txfiremank5

    txfiremank5 1/2 ton status

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    Well, if the 10 bolts are the orignal stock axles, then you should have 30 spline carriers. But if you don't know if they may have been swapped out, then you'll have to count. I'm not aware of any RPO code that would designate a 30 spline vs. a 28.
     
  9. RockinChevy

    RockinChevy 1/2 ton status GMOTM Winner

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    That's some dedicated five year old thread digging! First time I tried it, I dug as far back as 3 months then quit. Then became a paid member so I don't have to dig deeper....
    But still you found some good input....

    In that case, I'm sticking with my 4.10s instead of regearing to 5.13s with the 37's I plan on buying. I'm going for 203/205 doubler so 5.13s won't be necessary.
     
  10. 454k30

    454k30 1/2 ton status GMOTM Winner

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    who cares swap it for a dana60!
     
  11. 6.2Blazer

    6.2Blazer 1/2 ton status

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    The stock front axle on a '90 would be 30-spline. You can always give the VIN to the parts guy at a dealership and he can verify.

    Even with no towing or anything, the 3.08 gears are gonna' suck. The OD in the trans is going to be pretty much useless because the engine won't be able to lug the weight of a Suburban around at such as low rpm.
     
  12. muddybuddy

    muddybuddy 3/4 ton status

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    '89-91 were 30, all others are 28.
     

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