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Help ID this rear end...

Discussion in 'Differential & Driveline' started by TJ805, Apr 2, 2019.

  1. TJ805

    TJ805 Full Access Member

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    It's on a "73 K10 that I was told was "all original". Fortunately I got a deal, so no big. Pics are all I could find. No visible stamp on axle tube. I think it's a corporate, but really want to know if it is posi. I will eventually get into it, but hope someone can give me info based on these castings.
    -Thanks to all!

    I think the first pic is the birthday of 8-25-1976

    IMG_4296.JPG

    IMG_4297.JPG

    IMG_4301.JPG
     
  2. Blue Ox

    Blue Ox Turning Diesel Fuel Into Fun

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    A picture of the entire cover would help a lot.
     
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  3. dvdswan

    dvdswan Full Access Member

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    picture of the diff cover should identify what model it is.
     
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  4. hoagster

    hoagster Full Access Member

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    You'll have to clean all the snarf off of it, but on the other side of the 3896839N stamp you'll have a GM55 stamp! About half way between the the shock tab and the 3896839n marking on the axle tube your will find the designator for for year and what gearing is installed. You can see examples of this on my build thread. But it looks light you have a gm55 12 bolt truck axle

    008.jpg
     
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  5. Craig Nedrow

    Craig Nedrow Junior Member

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    I have a 73 K10 and 73 K20. K10 truck has stock posi 12 bolt, (has the smaller pinion bearing compared to the car 12 bolt). K20 is a Dana 60. 12 bolt is identified easily by the 12 bolts holding the rear cover on. 14 bolt wasn't offered until later, but identified by the 14 bolt rear cover.
     
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  6. TJ805

    TJ805 Full Access Member

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    Sorry, Here's a pic.

    IMG_4285.JPG
     
  7. TJ805

    TJ805 Full Access Member

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    More pics. I found no GM55 stamp or casting.

    IMG_4297.JPG

    IMG_4295.JPG
     
  8. TJ805

    TJ805 Full Access Member

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    How do I find your build page? I'd love to check it out.
     
  9. bucket

    bucket Super Moderator Staff Member

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    That's a truck 12 bolt axle. There should be some numbers stamped into the front side of the passenger axle tube, those cane be used to determine ratio and whether or not the rear is open.

    I prefer just to pull the cover and see for myself. Then just fill it back up with fresh lube.
     
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  10. TJ805

    TJ805 Full Access Member

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    Yeah that's what I'm up to. Waiting on parts. I'll send pics of the guts asap.
    -Thanks
     
  11. hoagster

    hoagster Full Access Member

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  12. hoagster

    hoagster Full Access Member

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  13. TJ805

    TJ805 Full Access Member

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    Does the Pinion have a rubber spline washer, like the transfer case, that goes on before the nut? Seems like it would, but I'm hoping that it doesn't...
     
  14. TJ805

    TJ805 Full Access Member

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    Center section has a GM78 casting, along with 3896839N.
    What do you think I'm dealing with?
     
    Last edited: Apr 17, 2019
  15. TJ805

    TJ805 Full Access Member

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    Center section castings- 3896839N and GM78

    Ring Gear stamps- 326663N, GM36

    Carrier stamp NFGM86

    Was hoping for Posi, but looks like no...
     

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