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"New" '79 K5 questions from a newbie

Discussion in 'The Garage' started by jtexfisher, Jul 21, 2005.

  1. jtexfisher

    jtexfisher Registered Member

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    :D Just dragged home a "new" '79 K5 to test for a bit. It's a SB400 with a TH350. How do I know? SB400 on emissions sticker and I cleaned enuff to find the casting no's (F0502TLH). TH350 id'd by pan shape. Did they put these together from the factory?

    XFER case...looks to be a NP203 based on year, drain plug (or lack there of - has fill plug and no drain plug), and shifter pattern (lo loc-lo-N-hi-hi loc). The truck has locking hubs which I gather weren't there from the get go. Any way for sure to tell if the '203 has been modified for real part time? Were folks prone to just throw new hubs at 'em in a 1/2 effort to make 'em part time?

    Thanks gobs!!
    a bit confused,
    JTEX
     
  2. Mad-Dog

    Mad-Dog 1/2 ton status

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    Not sure if it is a facory 400 block.....

    The 203 is a full-time case (with a drain plug), that's why it has manual hubs.....

    The 203 has the shift linkage on the side of the case, the 205 has 2 shift shafts coming out the front of the case....
     
  3. diesel4me

    diesel4me 1 ton status Premium Member

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    Its a 400...

    I found the " TLH " engine code listed for K10-K20 1979 GM trucks,400 SB...also the same code for 75 and 77 C30 trucks...

    I have seen TH350's factory behind 400 small blocks factory--one was in a Chalet ,a blazer with a factory camper ..my 400 sb I had in my 74 K20 was from a 78 Suburban K10,and it had TH350 factory also--so did my K20,and despite many years of beatings while plowing,it took 15 years before it lost reverse--all the forward gears still worked fine..I would not worry about the TH350 being durable enough--if you treat it right,it will last a long time..

    The 400 has a "half moon" cutout on the rear of the harmonic balancer,and needs a weight on the flexplate too...its the only externally balanced small block chevy made(until 86 or so--I dont know about newer stuff)... :crazy:
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    203 trucks from the factory had slugs, not locking hubs. Easy way to check for the part time kit is to unlock the hubs and put it in Hi. If the truck moves it has a part time kit.

    Rene
     
  5. Mad-Dog

    Mad-Dog 1/2 ton status

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    This is a weak area for me...

    Ok..this is a weak area for me, my '79 came with a NP203 and manual hubs or locking hubs.
    When you say slugs....what does does that mean..?
    I thought you needed manual locking hubs with a full-time case because the front axle is constantly driven..... :crazy:
    I have a NP205 in my truck now with the manual hubs so i assume i have to manually engage the hubs after placing the transfer case in 4-lo....yes ?
    I could remove the manual hubs but i like to have individual control over each side.....
    Please correct me if i am wrong here, thanx :bow:
     

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