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10-Bolt, 3.42, 7 1/2", 26 Spline.

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Stylzz, Nov 13, 2002.

  1. Stylzz

    Stylzz Registered Member

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    10-Bolt, 3.42, 7 1/2\", 26 Spline.

    I know they are found in S series trucks but are they found in other GM vehicles? What ones? And, how to tell the difference between 7 1/2" and 8 1/2" without measuring the ring gear?
    Thanks,
    Joe
     
  2. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    Re: 10-Bolt, 3.42, 7 1/2\", 26 Spline.

    I believe the 7.5 came in S-10's until 87-88 then replaced with a 7 5/8" gear. Same housing though.. Other cars that had were the camaro, malibu, el camino... All early 80's

    The 8.5" has a more rounded bottom to the housing/carrier. The 7.5" is not a round shape, its more of a taper to the middle of the housing/carrier.

    The way I tell is that a 7.5" ten bolt is shaped like the semi floater 14Bolt. The 8.5" is all on its own. Much more rounded. The 12bolt is shaped like a much smaller 14Bolt Full floater.

    Hope it helps,
    John
     
  3. u2slow

    u2slow 1/2 ton status

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    Re: 10-Bolt, 3.42, 7 1/2\", 26 Spline.

    This is the best link I could find:

    http://tech.oldsgmail.com/axle_ident.html

    The 7.5" has 26 spline axles, and the 7-5/8" has 28 spline.

    The only 8.5" rear end you are going to find in an S10 is a 94-up model. Either a ZR2 (which is wider than regular 4x4) or a 2wd 5-speed truck with a 4.3L.
     
  4. Stylzz

    Stylzz Registered Member

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    Re: 10-Bolt, 3.42, 7 1/2\", 26 Spline.

    Hey thanks a lot guys I just didn't want to be buying a 8.5 by accident. I currently have the 7.5 in my race car and wanted to put together a couple spares to have laying around. Anyone know what they go for complete, housing, axles, gears, etc?
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: 10-Bolt, 3.42, 7 1/2\", 26 Spline.

    I bought a posi 7.5 for 4125 about 5 years ago. The problem with the 7.5's are that they weren't used in anything that was performance, EXCEPT the Monte SS from '83-88, and that was 3.42 '83-84, and then 3.73 for 85+, and I believe Camaro as well, for some years. So, the 3.42 is "rare" and the 3.73 is "desirable" so they both go for $$ too.

    The 8.5 mid size car (442,'84 H/O,84+ GN) axles are difficult to find and $$$ as well. Difference being the width of the entire assembly, basically none interchange between different "size" cars and trucks. (Caprice, Camaro, Monte, and S-10's can't share axles)

    In a race car, it shouldn't be too tough to fit another size axle in there, (width wise) and the S-10's got much better ratios, although they had a gov-lock if they were "posi". Cars got actual posi.
     

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