1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

12 bolt rear end identification searched everywhere!!

Discussion in 'Differential & Driveline' started by Ryc10, Oct 23, 2020.

  1. Ryc10

    Ryc10 Junior Member

    Posts:
    4
    Likes Received:
    1
    Joined:
    Oct 23, 2020
    Location:
    Maine
    First Name:
    Ryan
    Truck Year:
    1976
    Truck Model:
    Chevy c10
    Engine Size:
    350
    Code on passenger side axle reads HA0426



    Other codes Nf3896838
    Gm56
    any help I’ve searched all the charts and no luck

    upload_2020-10-23_22-14-26.jpeg
     
  2. Ryc10

    Ryc10 Junior Member

    Posts:
    4
    Likes Received:
    1
    Joined:
    Oct 23, 2020
    Location:
    Maine
    First Name:
    Ryan
    Truck Year:
    1976
    Truck Model:
    Chevy c10
    Engine Size:
    350
    Sorry just noticed posted it under wrong category don’t know how to change it
     
  3. bucket

    bucket Super Moderator Staff Member

    Age:
    39
    Posts:
    22,453
    Likes Received:
    8,388
    Joined:
    Aug 3, 2010
    Location:
    Usually not in Ohio
    First Name:
    Andy
    Truck Year:
    '77, '78, '79, '84, '88
    Truck Model:
    K5 thru K30
    Engine Size:
    350-454
    Moved it for ya.

    I'm no help with the numbers, but I wouldn't be afraid to pull the cover for an inspection. That will tell you exactly what you have and you can put fresh fluid in.
     
  4. rpcraft

    rpcraft Full Access Member

    Posts:
    1,131
    Likes Received:
    360
    Joined:
    May 31, 2016
    Location:
    Texas
    First Name:
    Robert
    Truck Year:
    1985
    Truck Model:
    Jimmy
    Engine Size:
    0.0
    From what I remember the stamping on the axle tubes has nothing to do with the carrier or R&P. I can't recall all the numerical data on it but it just comes down to a production serial date. The internals would have been on the tag in the glove box with a metal tag on the lower bolt on the diff cover but a lot of people took them off during a service and for some reason never thought it was important to put them back on.
     
  5. fast68chevy

    fast68chevy I am the original fast68chevy

    Posts:
    125
    Likes Received:
    48
    Joined:
    Oct 17, 2020
    Location:
    LINCOLN IL
    First Name:
    RANDY
    Truck Year:
    1975
    Truck Model:
    C20
    Engine Size:
    350
    well you remember wrong.,. the prefix letters stamping has everythign to do with the ratio, and whats what these letters stampings are for exactly... most GM truck axles werent tagged like many of the dana and ford axles were. a tag on the fill plug on the posi/lim slip equipped axles was about the only time you saw a tag on the 12 bolts.. otherwise no tag on these axles.

    the HA prefix stamp code is for the ratio

    HB,LL,RA.TR,TT,TU are 3.07s

    HA,HJ,HQ,MF,TQ,MI,MK are 3.73s

    HK,HL,HR,ME,MG,TS are 4.11s

    HC,HN,MU are 3.73 Posi

    HO,HP,JQ, are 4.11 Posi


    the four numbers are the julian date.

    0426 is the 42nd day of 1976


    call local dealer parts counter with that code and year make model and they can tell you what it was from factory... if its the original axle anyways.. it was a 1976 3.73 open carrier

    and in these 12 bolt truck axles you would rather have open diff than the G80 gov lok, AKA grenade-lok
     
    Last edited: Oct 25, 2020
    Turbo4whl, Vbb199 and HotRodPC like this.
  6. HotRodPC

    HotRodPC Administrator Staff Member

    Posts:
    45,816
    Likes Received:
    6,183
    Joined:
    Aug 29, 2010
    Location:
    OKC, OK
    First Name:
    HotRod
    Truck Year:
    85 K20 LWB / 86 K5
    Truck Model:
    Silverado / Silverado
    Engine Size:
    454 - Turbo 400 - 3.73 350 - 700R4 - 4.10
    Last edited: Oct 25, 2020
    bucket likes this.
  7. HotRodPC

    HotRodPC Administrator Staff Member

    Posts:
    45,816
    Likes Received:
    6,183
    Joined:
    Aug 29, 2010
    Location:
    OKC, OK
    First Name:
    HotRod
    Truck Year:
    85 K20 LWB / 86 K5
    Truck Model:
    Silverado / Silverado
    Engine Size:
    454 - Turbo 400 - 3.73 350 - 700R4 - 4.10
    I'm wondering if this 12 bolt is even a truck 12 bolt. Is this installed in your truck now?
     
  8. dvdswan

    dvdswan Full Access Member

    Posts:
    1,548
    Likes Received:
    980
    Joined:
    Mar 11, 2014
    Location:
    Port Orchard, WA
    First Name:
    Dave
    Truck Year:
    1978
    Truck Model:
    K10
    Engine Size:
    350
    Best way to find out the type of rear end is usually the shape of the cover...

    Differential-ID-Chart-Page-e1348182057479.png

    as for the gears, the best way is to pop the cover and read the stamp on the ring gear...

    axle ratio ring gear.jpg

    while its open you can identify what type of carrier you have as well.
     
    78C10BigTen likes this.
  9. Ryc10

    Ryc10 Junior Member

    Posts:
    4
    Likes Received:
    1
    Joined:
    Oct 23, 2020
    Location:
    Maine
    First Name:
    Ryan
    Truck Year:
    1976
    Truck Model:
    Chevy c10
    Engine Size:
    350
    Yes
     
  10. Ryc10

    Ryc10 Junior Member

    Posts:
    4
    Likes Received:
    1
    Joined:
    Oct 23, 2020
    Location:
    Maine
    First Name:
    Ryan
    Truck Year:
    1976
    Truck Model:
    Chevy c10
    Engine Size:
    350
    Yes it’s in the truck now. The motor in the truck was a 305 out of a 76 Camaro but the rear end is def a truck 12b

    C8BE89D0-6B47-4048-A507-FEC1CAE43EFB.jpeg
     
    bucket likes this.
  11. AuroraGirl

    AuroraGirl Supporting Member Supporting Member

    Age:
    22
    Posts:
    3,468
    Likes Received:
    1,942
    Joined:
    Sep 8, 2019
    Location:
    Northern Wisconsin
    First Name:
    Taylor
    Truck Year:
    1978, 1980
    Truck Model:
    K10, K25
    Engine Size:
    400(?), 350
    Wdym? I have a 79 stepside 1/2 frame that was made into a truck bed trailer. At least I think its a 79. But it has a 12 bolt with G80 on the cover :O
     
  12. AuroraGirl

    AuroraGirl Supporting Member Supporting Member

    Age:
    22
    Posts:
    3,468
    Likes Received:
    1,942
    Joined:
    Sep 8, 2019
    Location:
    Northern Wisconsin
    First Name:
    Taylor
    Truck Year:
    1978, 1980
    Truck Model:
    K10, K25
    Engine Size:
    400(?), 350
    That would be a 12 bolt right?
    Snapchat-1968402799.jpg

    It says G80 on the cover
     
    HotRodPC likes this.
  13. HotRodPC

    HotRodPC Administrator Staff Member

    Posts:
    45,816
    Likes Received:
    6,183
    Joined:
    Aug 29, 2010
    Location:
    OKC, OK
    First Name:
    HotRod
    Truck Year:
    85 K20 LWB / 86 K5
    Truck Model:
    Silverado / Silverado
    Engine Size:
    454 - Turbo 400 - 3.73 350 - 700R4 - 4.10
    Someone must have put the G80 on the cover. Is it hand written or engraved? The factory doesn't mark them generally.
     
  14. AuroraGirl

    AuroraGirl Supporting Member Supporting Member

    Age:
    22
    Posts:
    3,468
    Likes Received:
    1,942
    Joined:
    Sep 8, 2019
    Location:
    Northern Wisconsin
    First Name:
    Taylor
    Truck Year:
    1978, 1980
    Truck Model:
    K10, K25
    Engine Size:
    400(?), 350
    it says GM80 in the stamped portion to the right of the center
     
  15. HotRodPC

    HotRodPC Administrator Staff Member

    Posts:
    45,816
    Likes Received:
    6,183
    Joined:
    Aug 29, 2010
    Location:
    OKC, OK
    First Name:
    HotRod
    Truck Year:
    85 K20 LWB / 86 K5
    Truck Model:
    Silverado / Silverado
    Engine Size:
    454 - Turbo 400 - 3.73 350 - 700R4 - 4.10
    That's probably just a casting # if it's GM80, not G80.
     
    AuroraGirl and bucket like this.

Share This Page