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NP-203

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by MR.4x4, Jul 18, 2002.

  1. MR.4x4

    MR.4x4 Registered Member

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    Hi, i have a Blazer 1975, automatic with a 350 and a
    Transfer NP-203 and i dont know how it works!!
    I know this is a chain transfer, full time & it has a set of differential gears which allow for full-time operation; the differential
    action can be manually locked out.

    But when a wheel spins, all the power goes to that wheel, living me stuck!!
    How can i ``lock´´? my transfer??

    Thanks for your help. /forums/images/icons/smirk.gif
     
  2. azblazor

    azblazor 1/2 ton status Premium Member

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    Hi lock or LO lock position locks the transfer case differential.
     
  3. MR.4x4

    MR.4x4 Registered Member

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    Ok, but i dont know where are low lock or hi lock, i put my Stick shifter backest and foward but it dosnt lock!!!
     
  4. azblazor

    azblazor 1/2 ton status Premium Member

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    Full forward should be lo lock, full back should be hi lock, if I recall correctly. You may only need to adjust the shifter. Do you have a manual for it? Oh and can you fill out your profile some more?
    Thanks
    Mark
     
  5. Muddytazz

    Muddytazz 1 ton status

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    Yes full forward and full back is the loc positions. I have a 75 burb with a np203 full-time, without tearing the diff cover off, how can you tell if there is a locker in?
     
  6. 4x4Freak

    4x4Freak 1/2 ton status

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    Full forward is Low Lock and full back is High Lock. Try oiling the shifter, thats all my K10s problem was when I first got it.
     
  7. MTPockets

    MTPockets 1/2 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    But when a wheel spins, all the power goes to that wheel, living me stuck!!
    How can i ``lock´´? my transfer??


    [/ QUOTE ]
    the transfer case doesn't have a locker in it. your wheel spin issue is due to the fact you still have open differentials. without some type of differential locker, in an extreme situation, you will only have one front tire and one rear tire spinnin'.

    my experience with the 203 is that if the shifter is not adjusted right it will 'pop' out of low loc...leaving you in two wheel drive, when you need 4wd the most.
     
  8. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Check these things first.

    1st: do you have manual locking hubs, if so your front wheels will not be under power until you lock BOTH hubs in, (assuming no locker in front axle, and no broken hubs).
    2nd: Is your front driveshaft installed/hooked up. Some people (maybe a previous owner) remove the front driveshaft to eliminate wear and tear on it and the front end if the t-case is not convertered to part time (i.e. still a full time unit)
    3rd: Make sure you are getting the shifter to move through it's full range of motion. Normal operation of the 203 is 4hi loc (one front AND one rear tire should spin), 4 hi (one front OR one rear tire should spin), N, 4 low one front OR one rear tire should spin), 4 low loc (one front AND one rear tire should spin) this is assume stock open differentials front and back. You should be in the loc position with the shifter all the way forward or all the way back. Also affected by shifter linkage. If you have a body lift installed, it may be causing you problems and the shifter linkage may need to be adjusted.

    Hope this helps.
     
  9. HarryH3

    HarryH3 1 ton status Author

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    Here's the shift pattern for a 203 that hasn't been modified for part time operation:

    Front of truck

    4 Lo Loc
    4 Lo
    N
    4 Hi
    4 Hi Loc

    Either of the Loc positions simply locks the front and rear driveshafts together, forcing them to rotate at the same speeds. It doesn't do anything to the axle differentials, so it's still possible to spin just one tire on each axle.
     
  10. Muddytazz

    Muddytazz 1 ton status

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    So with the 203, there is no real way to get all 4 tires to spin without the install of lockers?
     
  11. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Technically Yes you can (engine producing insane amounts of torque/Hp and parasitic drag overcoming the static friction of the wheel on the ground......not likely we will EVER see that), in the real world no way (even with a healthy big block). Even if you could get all 4 tires to spin, they would not be driven equally (due to bias in the differentials). With no lockers, open diff, and t-case in loc position you will only spin two tires......3 tires if one axle is locked, and 4 tires is both axles are locked.
     
  12. MR.4x4

    MR.4x4 Registered Member

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    Thanks everyone for your help!!!
     

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