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Help! axle splines different between 87 and 91 10 bolt front diff?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by FastEddy, Apr 6, 2001.

  1. FastEddy

    FastEddy 1/2 ton status

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    I have an 87 suburban 1/2 4x4 with the 10 bolt diff. tore up drivers side inner and outer axle shafts, so went and bought a set (front and rear) diffs out of a 91 blazer 4x4, and just tried to put the axle shaft assbly in my 87 diff and the inner splines are different that engage in the side gear of the pumpkin. if my counting is correct one is 28 spline (the 87) and the one out of the 91 is 30 spline. I was under the impression that all front 10 bolts are the same. both diffs have the round cover , not the straight sided cover on the dana 44, which i have one on the yard in my 74 to compare to. what gives. what year did they change? can i just pull my cover and change the side gears over too? hate to change the whole diff this afternoon, especially since i am not even sure of the ratios being the same yet. hoping to get an answer right away, as the sub is apart, and i'm gettin' grease all over my computer. I would rather fix the burb and get it dirty today, the plowed field next to me is calling me to go play, it's covered with water, but still probably frozen a few inches underneath, making for some nice sliding at speed. thanks in advance...ED
     
  2. Blazer1970

    Blazer1970 1/2 ton status

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    Front and rear both changed in '89, I think. The carrier is different also for the 30 spline version, so changing only the side gears is not an option.

    Tim

    70 Blazer CST 4X4 350 SM465 NP205
    87 Burb 4X4 350
    01 GMC 2500HD 4X4 Duramax/Allison
     
  3. wayne

    wayne 3/4 ton status

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    The cover for the 10 bolt is the same. They wen't to 30 spline in 89 so the carrier is diff. too. You need the older ones or swap everything from the 30 spline rears. If you can get the rears out of the truck you pulled the axles from and they have the same gears that you have now or better ones, just bolt them in and go. Don't forget to get a front end alignment if you swap rears.

    <A target="_blank" HREF=http://jamonline.homestead.com/fromthegroundupK54x4/89Jimmy.html>http://jamonline.homestead.com/fromthegroundupK54x4/89Jimmy.html</A>
    <font color=blue>Happy Trails<font color=blue>
    <font color=blue>Wayne<font color=blue>
     
  4. HispanicPanic

    HispanicPanic 1/2 ton status

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    correct me if im wrong guys but i thought it was in 88 that went to 30 spline?

    <A target="_blank" HREF=http://jimjim.coloradok5.com>http://jimjim.coloradok5.com</A> [​IMG]
     
  5. wayne

    wayne 3/4 ton status

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    You may be right. 88 to 89 was a change over year for alot of parts so I think it just depends when they were made. My 89 still has some 88 parts on it. I found out when installing a radio the plug I bought was for an 89 to 91 and it did not fit so I got one for up to an 88 and it was the one.

    <A target="_blank" HREF=http://jamonline.homestead.com/fromthegroundupK54x4/89Jimmy.html>http://jamonline.homestead.com/fromthegroundupK54x4/89Jimmy.html</A>
    <font color=blue>Happy Trails<font color=blue>
    <font color=blue>Wayne<font color=blue>
     
  6. 6.2Blazer

    6.2Blazer 1/2 ton status

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    According to the GM parts book, the front 10-bolts went to 30 spline axles in '89. I think the rear 10-bolts started switching over a year or so earlier......but it's hard to tell for sure with GM.

    I'm not sure about the carriers being compatible as I believe the 30-spline carriers were machined out to accept the larger 30-spline axles.....though I'm not really sure as to what exact part this was and if the side gears would be interchangeable.

    On the bright side, the outer shafts (stub shafts) and u-joints are the same between the 28 and 30 spline versions.

    My recommendation would just to buy a set of 28 spline shafts. There are easy to find and pretty cheap around here.

    BTW, if you want to sell the 30-spline front shafts I might be interested..............
     
  7. FastEddy

    FastEddy 1/2 ton status

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    thanks to all who replied to my post. first I found out the axle wouldn't fit in the side gear, then I tried swapping side and spider gears from the 91 into the 87, great, the fit. reassemble, go to slide the axle in, same thing. the carrier needs to be changed, because the centre where the axle slides through to go into the side gear is not machined big enough to accomodate the 30 spline axle. fine. change the carrier, set up the gears. bingo, the axles slide right in. double check the outers to see if they fit into the hubs, etc. perfect. bolt on the spindle, remove spindle, place backing plate on spindle, then bolt up the spindle, can almost taste the cold beer now. not so fast. the rotors won't go on now, because i used the 91 spindles, and want to use my 87 new rotors, but the inner wheeel bearing is different. remove spindles, use 87 spindles, reassemble, put rotors/hubs, wheels, etc back on. front cover, gear lube. went out and got her dirty. works good. should have just changed complete diff. it started out as just an axle shaft change.....another drawback is i can't use my posi carrier now in the front, until i get some axle shafts, then convert everything back to 87 style.....stamp collecting as a hobby instead of off roading was looking pretty good yesterday....but I'm better now.....live and learn...ED
     

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