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30 spline axles

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by K5Mudbug, Jan 3, 2001.

  1. K5Mudbug

    K5Mudbug Registered Member

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    Will changing a 10 bolt axle from a 28 count spline to a 30 count spline make a big difference. I am turning 35 inch tires, and want to change the axles to 30 count spline with a 4.56 gear ratio and with ARB lockers front and rear, is it possible, and would this be about the same as going with say a 12 bolt , fixed the same way (30 cnt spline, 4.56 and ARB)?

    I really want to use what is there, It is a 88 model with a 700R4 tranny. If I do have to buy new axles I am gonna gut 1 ton stuff but I dont want too. I would also appreciate any info on how to the install I talked about. I am also considering using the Warn full float kit in the rear. Gonna be doing this project over time cuz its expensive.

    2000 S-10 ZR2, in process of getting a 88 K5 with a 6 inch lift and 35s
     
  2. HarryH3

    HarryH3 1 ton status Author

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    I don't know how much difference there is in strength but the 30 spline is a slightly larger diameter axle shaft. That alone should make it stronger. A 14-bolt FF is WAY stronger, available cheap (if you shop around) and literally bolts into place. You'd have to go with a Detroit Locker though since the ARB isn't available for it.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  3. 6.2Blazer

    6.2Blazer 1/2 ton status

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    The 30-spline 10-bolt shafts are the same strength as the 12-bolt shafts, so yes it will make a difference. If you also go with aftermarket alloy units (such as those available from Moser), you will greatly increase the strength of the axle shafts.
    Also, an aftermarket diff (ARB in your case) and gears should also beef up the 10-bolt. I have no personal experience with ARB's, but the "rumors" floating around our club is that they don't hold up quite as well as something like a Detroit in the rear axle.

    While I do recommend running 30 spline shafts in the rear 10-bolt, I don't recommend converting the front over to 30 splines. While there is some strength increase in the actually shaft, the u-joints are still the same and seem to often break first anyway, 30-spline FRONT axles are more expensive and hard to find in the junkyards. You could always go to ORD's chromoly front axle shafts. Even the 28 spline versions are suppposedly much stronger than the u-joints so there really isn't much advantage to going to 30 splines in the front.
     
  4. K5Mudbug

    K5Mudbug Registered Member

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    I think for now I am just gonna regear the axles to 4.56 ratio and put warn premium hubs up front. Later when I get the money I am gonna change the rear to 30 spline. I am gonna go with warn stuff cuz I can get it real cheap. The Full float kit comes with 30 spline axles, What do I have to do to make this work in a 28 spline axle? Doesnt the axle connect to the differental, which would be the 30 spline ARB unit i would e buying also? I dont want a Detroit locker, I know they are good, but a ARB has a lifetime warranty and I get instant positve traction when I need it, And only when I need it. BAck to question, What all parts do I have to change out to add 30 spline full float kit by warn and a 30 spline ARB, and will the 4.56 gears I install now work when I make the axle change? Thank you very much for helping me.

    Oh yeah, warn also makes front axles for a 10 bolt I think, they are 28 sp. and alot stronger arent they? also, my K5 is an 88, Would this make the axles different from a 87, cuz warn application charts only show listings up to 87, but I think the 10 bolt axles are the same, arent they? Thanks a bunch.

    2000 S-10 ZR2, in process of getting a 88 K5 with a 6 inch lift and 35s
     
  5. rock.monkey

    rock.monkey 1/2 ton status

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    Are you positive you have 28 spline axles in your 88??
    My 88 came with 30 spline front and rear.

    Bill Innes
    88' Jimmy
    [​IMG]
     
  6. K5Mudbug

    K5Mudbug Registered Member

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    I just asumed, I have only owned it a day now. The chart on this website says it did, so I took that as truth. I am ordering the gears in a couple of weeks, I will check on it then I guess, The only thing I know for sure is that it is a 3.73 gear ratio.

    2000 S-10 ZR2, in process of getting a 88 K5 with a 6 inch lift and 35s
     
  7. 84k5

    84k5 1/2 ton status

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    88 was the transition year from 28 to 30 spline axles so dependding at what time during the year yours was built you could have either.

    Brian
    84k5
     
  8. K5Mudbug

    K5Mudbug Registered Member

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    Ok, so does this mean I wont be able to install the warn full float kit, there application guide only goes up to year 87, But if there are 30 spline, I probally wont worry with that.

    2000 S-10 ZR2, in process of getting a 88 K5 with a 6 inch lift and 35s
     
  9. coopertwpk

    coopertwpk 1/2 ton status

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    My blazer has 30 spline ,next month its getting a 14ff and d44 both 3/4t 8 lug
     
  10. Hobbes68

    Hobbes68 Registered Member

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    FYI, 1988 was a transition year. Early 1988's had 28 spline axles and late 1988's had 30 spline axles.
     
  11. K5Mudbug

    K5Mudbug Registered Member

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    So does that mean that the axle assembly is the same, They just changed the spline count, Or are the bearings all different. I would really like to know what all was changed. If someone has a 12 bolt with 4.56 gears they would not mind selling , I would be interrested in that now that I found out there was a change. When I open it up to change the gears I look and see what its got.

    2000 S-10 ZR2, in process of getting a 88 K5 with a 6 inch lift and 35s
     
  12. 6.2Blazer

    6.2Blazer 1/2 ton status

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    I believe the only difference between the 28 and 30 spline 10-bolts was the carrier. You might also want to double check the bearings, but if you are installing new gears and a locker you should replace all of the bearings anyway.
    '89 was the first official year for the 30-spline axles, but with GM it's not surprising to find '88s with 30 spline also.
    If you install 4.56 gears now, and then upgrade to an ARB and Warn full-float kit later, you will be able to re-use the gears. However, if you are paying a shop to install the gears now, you will have to pay for the labor again when the ARB goes in.
    Yes, the Warn kit should work with the '88 year axle. It's common to see parts listing only go up to '87 since they changed the pickups to a different style in '88, and the drivetrain of the pickups and Blazers were almost exactly the same except for the '88-'91 model years. I've had a lot of trouble getting parts for my '90 K5 because places try to give stuff to fit the '88 and newer pickups with IFS.
    If you currently have 28 spline axles, also keep in mind that you will have to do the ARB and Warn kit at the same time if you go with 30 spline axles.
    The ORD chromoly front shafts, even in the 28 spline version, should be substantially stronger than stock. According to conversations with Stephen Watson of ORD, there's no reason to go to 30 spline chromoly axles in the front because the u-joint strength cannot be increased.
     
  13. K5Mudbug

    K5Mudbug Registered Member

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    Thanks alot for the info, you helped alot but another one

    "Yes, the Warn kit should work with the '88 year axle. It's common to see parts listing only go up to '87 since they changed the pickups to a different style in '88, and the drivetrain of the pickups and Blazers were almost exactly the same except for the '88-'91 model years. I've had a lot of trouble getting parts for my '90 K5 because places try to give stuff to fit the '88 and newer pickups with IFS."

    What is different in the 88-91 year models drivetrain wise?


    2000 S-10 ZR2, in process of getting a 88 K5 with a 6 inch lift and 35s
     
  14. coopertwpk

    coopertwpk 1/2 ton status

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    the 700rs where upgraded the 90sand 91s came with np208 and some with np241 which oils better i guess the 87 newer came with TBI and a different rear main bearing and seal(one stupid piece)<font color=red>IDIOTS</font color=red>that means the tranny has to come out to replace it.also almost all the suspension bolts are larger (9/16") making bushings harder to find also they are not k5 blazers they are <font color=red>V10</font color=red> blazers

    88k5 silverado w4"lift soon to have <font color=orange>d44 and corp14ff</font color=orange> with 4.56s
     
  15. 6.2Blazer

    6.2Blazer 1/2 ton status

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    There were really only minor changes made to the '88-'91 Blazers. Some of these included the appearance of the NP 241 case, 30-spline axleshafts, and a few other odds and ends....but in general the vast majority of parts were interchangeable with pre'88 model years.
    What I was trying to say in my previous statement was that ever since the introduction of the Blazer, most of the parts were interchangeable with the pickups up until '88 when the new pickups were introduced. Then in '92 the Blazer was changed to match the pickups and again most of the parts were interchangeable, so only the '88-'91 Blazers and pickups have substantial differences. The problem seemed to be that most automotive shops, parts stores, and even tire stores (at least in my experience) associated Blazers with always sharing the same parts as the pickups. I guess it's not really that the parts for my '90 were not available, but rather the parts stores tried to give me parts for a '90 pickup, which in most cases will not work. Just one example is when I ordered new rims from a big tire shop. I specifically told them what sized lug nuts it needed, and that the front center caps had to be open in order to accomodate the front locking hubs. A week later when I went to have them installed, they had went ahead and ordered lug nuts to fit a '90 pickup (which used a metric size) and front center caps that were closed ('88 and newer pickups don't have locking hubs). The sales guy even tried to argue with me and I finally had to actually show him those parts wouldn't work.
     

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