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1979 K25 Automatic NP203 or NP205

Discussion in 'Transmission & Transfer Case' started by Loww, Jan 10, 2019.

  1. Loww

    Loww Junior Member

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    Location:
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    First Name:
    Dominic
    Truck Year:
    1979
    Truck Model:
    GMC K20
    Engine Size:
    5.7
    Hi,

    I'm about to buy a 1979 GMC K25 . I read, that the 1979 Automatics had Full-Time 4WD and the NP203 transfer case. But this one has manual locking hubs on the front wheels and the transfer case lever has four positions: 4L, N, 2H, 4L. Did GM switch to the NP205 during the model year 1979 or how can this be explained?

    Thanks
     
  2. Charlie

    Charlie Full Access Member

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    Truck Year:
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    Truck Model:
    Cheyenne 10 LWB
    Engine Size:
    350/TH350/AC/4 BBL Quadrajet
    :welcome:
     
  3. K201979

    K201979 Full Access Member

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    Location:
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    Hippie
    Truck Year:
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    Truck Model:
    K20
    Engine Size:
    350ci
    Not sure on that but my 79k20 has th400/203. I put manual hubs on so i could use high lock to get around while i was saving for a front shaft and not b turning the front diff. The 4 positons on the stick does tell me 205 tho. Someone probly swaped it. Welcome!
     
  4. bucket

    bucket Super Moderator Staff Member

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    Truck Year:
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    Truck Model:
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    Engine Size:
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    In 40 years, there's a lot of parts swapping that could have went on. Many (most actually) would call the 205 an upgrade.
     
  5. dvdswan

    dvdswan Full Access Member

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    First Name:
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    Truck Year:
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    Truck Model:
    K10
    Engine Size:
    350
    Some vehicles were order with auto trans and manual hubs. So this is not unheard of. A friend had a 80 Jimmy with manual hubs and 205 from the factory, his father ordered it that way. Yes, IMO, it is an upgrade since it is an all gear t/case.
     
  6. bucket

    bucket Super Moderator Staff Member

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    All '80 models came with the 205 and locking hubs, there was no other option that year.

    Other than '73 models, '80 models, and 6cyl trucks some years, trucks with automatics got the 203 case and no locking hubs.

    Many many many 203 trucks had locking hubs swapped in, often times without the 203 being converted. And in the decades since then, many trucks have had the drivetrains swapped a time or two. Or three or four even.
     
    Last edited: Jan 10, 2019
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  7. Loww

    Loww Junior Member

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    Dominic
    Truck Year:
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    Truck Model:
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    Engine Size:
    5.7
    Thank you! Is it an easy swap (205 for a 203)? I mean, is it like experimental or more like a standard modification? Will it make future repairs more difficult, because of non-standard parts?
     
  8. dvdswan

    dvdswan Full Access Member

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    Engine Size:
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    Curious, why do you want to go to a 203? They are heavier, have a chain, and linkage needs to be adjusted periodically. 205 is lighter, gear driven, simple, and strong. Swapping the 2 you will need the correct trans to t/case adapter and change your drive shafts IIRC.

    Learn something new everyday. I never knew this.
     
  9. mgarland

    mgarland Junior Member

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    Truck Model:
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    Big
    Don't worry about the 205 and future repairs, if you change the fluid in it and it looks ok then run it and don't look back. It was the best case GM ever put in a truck and they a virtually trouble free.
    Mark
     

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