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NP203 questions

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by wheelnut46, Dec 30, 2001.

  1. wheelnut46

    wheelnut46 1/2 ton status

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    I keep reading that the NP203 can be a good transfer case if properly maintained and read on a recent post that it needs to be driven in Hloc every so often. I have a NP203 that was converted to part time (Warn hubs) by the first or second owner (I’m #4). The last PO had the transfer case rebuilt about 6 years ago (about 6,000 miles ago) and was wondering what the rules are exactly. Except for this conversion, I believe the truck to be completely stock.
    I have always been very careful with my other trucks not to use 4 wheel drive on patches of dry road. I even haven’t used it on seemingly wet / icy road because of the threat of snapping (torsional failure) of an axle. Now that I have a NP203 does that mean that I can lock the hubs and throw it in Hloc and be done with it? Can I shift from H to Hloc while moving? Does it have to be in Neutral (coasting or completely stopped) So many questions. Obviously the owners manual doesn’t state the rules for driving with a converted truck.


    Bill
    '77 GMC Jimmy
    '46 chevy pickup
    '67 Chevelle Malibu
     
  2. m j

    m j 1/2 ton status

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    you have hubs?

    formerly 77chev
     
  3. wheelnut46

    wheelnut46 1/2 ton status

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    yes, Warn locking hubs. It was already converted when the guy I bought it from got it.

    Bill
    '77 GMC Jimmy
    '46 chevy pickup
    '67 Chevelle Malibu
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Did he actually do the T-case conversion or just throw on some locking hubs and call it a day?

    I had a 77 Blazer that the PO claimed had been converted but all it had was warn hubs and an untouched T-case.

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
    <a target="_blank" href=http://coloradok5.com/gallery/project_T2> tRusty pics...</a>
     
  5. wheelnut46

    wheelnut46 1/2 ton status

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    how do I tell? I'm sure the old retired guy I bought it from doesnt know either.

    Bill
    '77 GMC Jimmy
    '46 chevy pickup
    '67 Chevelle Malibu
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Unlock the hubs, put the T-case in HI. if it has a part time kit the front shaft should spin easily by hand with the truck in park. If it's not converted you won't be able to turn the shaft.

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
    <a target="_blank" href=http://coloradok5.com/gallery/project_T2> tRusty pics...</a>
     
  7. wheelnut46

    wheelnut46 1/2 ton status

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    Yes the shaft spins with the truck in Park and the hubs unlocked. I guess that means its been converted. So what are the rules and capabilities of this setup? I bought this truck for a daily driver so its gonna see snow and bad weather on the road mostly. It may also tow a small trailer.

    Bill
    '77 GMC Jimmy
    '46 chevy pickup
    '67 Chevelle Malibu
     
  8. johnnyK5

    johnnyK5 Registered Member

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    There is a post from 12/21/01 by Calclips that got some very good responses regarding your t-case. The post is near the bottom of page 9 right now.

    " IT AINT DEEP !! " -common phrase from that guy who doesn't drive to the local mudhole.
     
  9. wheelnut46

    wheelnut46 1/2 ton status

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    OK, NOW I'm confused. I read the post on page 10 from Calclips and printed some out for future reference but what confused me was the statement that now that its converted it has 2WD LOW. ?????
    So I drive around every day with the T-case in H, hubs unlocked. If it snows I drive in HLOC? With the hubs locked right? Thats 4 wheel High? I have to drive in HLOC every 200 miles - hubs unlocked. Thats 2WD High too right?
    L is now 2WD Low? (hubs unlocked) Can I lock the hubs in L?
    L-Loc is 4wd low? (hubs locked)
    So the only time I lock the hubs now is when Its in H-Loc (but I'm not just running it to lube) or in L-Loc (4 low)
    Is all that right?
    I feel like I'm in an Abbot and Costello routine - whos on first?
    I think this makes sense but cant be sure.

    Bill
    '77 GMC Jimmy
    '46 chevy pickup
    '67 Chevelle Malibu
     
  10. wheelnut46

    wheelnut46 1/2 ton status

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    So can I drive this thing in HLOC (4wheel High) on dry pavement like it was designed to do? Or since it was converted is that out of the question now?

    Bill
    '77 GMC Jimmy
    '46 chevy pickup
    '67 Chevelle Malibu
     
  11. wheelnut46

    wheelnut46 1/2 ton status

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    I know that this is all very basic and maybe I should understand it by now but since this is completely different from any of my previous 4x4's I really need someone to break it down for me.
    I am very intersted in being able to drive around in 4 wheel drive even on dry pavement (So my wife can drive it to work in bad weather) but am not sure if it can still do that or not.
    Also the owners manual tells of matching engine speed when shifting the transfer case - whats that all about?

    Bill
    '77 GMC Jimmy
    '46 chevy pickup
    '67 Chevelle Malibu
     
  12. HarryH3

    HarryH3 1 ton status Author

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    If your t-case has been converted so that it now has a 2WD position, then the internal differential that allowed it to run on dry pavement in 4WD is no longer functional. It now behaves as a part-time 4WD system and will not allow the front and rear driveshafts to rotate at different speeds. So no, you can't drive it in 4WD unless the road is wet, icy or snowy.

    The statement about matching engine speed just applies to trying to shift to 4-lo while the truck is moving. I'd suggest that you not try this anyway. If you need to shift into 4-low, stop the truck, put the transmission in neutral and quickly shift to 4-lo, being careful NOT to stop at neutral in the transfer case. If you stop at the neutral position in the transfer case, then you'll have to either a) grind the gears to get it out of neutral or b) shut the engine off and shift. Sometimes it's easier to shift if the truck is just barely rolling as you shift. It's just something that you have to practice. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
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  13. johnnyK5

    johnnyK5 Registered Member

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    I have a factory setup and I have shifted from H to HLOC at 60-65mph on the interstate (on snow of course). The case can also be shifted from L to LLOC on the fly.
    Doing this with a converted case was not discussed and I am curious also since I plan to convert mine.

    " IT AINT DEEP !! " -common phrase from that guy who doesn't drive to the local mudhole.
     
  14. HarryH3

    HarryH3 1 ton status Author

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    Shifting from either range to the "Loc" position just locks out the internal differential, thus locking the front and rear driveshafts together. It's shifting between high and low range that gets tricky if you're moving, as there's a 2 to 1 difference in the gear ratios.

    Once you do the conversion on a 203, then you no longer have the normal H or L fulltime 4WD functions. It will be in either 2WD, 4WD (just like your Hi-Loc now), 4WD Low Range (just like your Low-Loc now) or Neutral.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     
  15. johnnyK5

    johnnyK5 Registered Member

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    So if I convert and go out on the trail with front hubs locked in and I have it in L - can I shift on the fly into LLOC?

    " IT AINT DEEP !! " -common phrase from that guy who doesn't drive to the local mudhole.
     
  16. m j

    m j 1/2 ton status

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    so knowing it is a 2:1 ratio it is fairly easy to shift at any road speed between the two ranges. I shift clutchless as it is easier to vary rpm of input shaft to match output shaft, shifting into low simply lift on throttle slightly to release driveline tension, shift into neutral, double engine rpm and it should slid in fairly easily. practice makes perfect.
    the range box doesnt have those annoying blocker rings that light trannies have so it will be much more difficult with the clutch then without.

    'loc' position was intended for conditions with less traction to allow tires to scrub of driveline tensions, I thought that wouldnt work after a conversion as it is always in loc now isnt it?

    formerly 77chev
     
  17. wheelnut46

    wheelnut46 1/2 ton status

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    So, to properly maintain this system I need to:
    Drive with the hubs locked (but the transfer case in H) once in a while to assure lubrication in the front end.
    Drive with the transfer case in HLoc (but the hubs UNLOCKED) once in a while to assure lubrication of the transfer case.
    With any other transfer case it was always stated that one could NOT drive with the tranfer case engaged (4WD) with the hubs unlocked or damage would result.
    Do I have a 2WD low now? If so, thats interesting. I wonder what to do with that?

    Bill
    '77 GMC Jimmy
    '46 chevy pickup
    '67 Chevelle Malibu
     
  18. m j

    m j 1/2 ton status

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    if you drive in 4hi hubs locked or not it will lube both TC and dif.
    still need to hear from those that have done the conversion whether loc does anything.
    I am going to have a look at the offroad.com tech on the subject

    formerly 77chev
     
  19. m j

    m j 1/2 ton status

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    <a target="_blank" href=http://www.off-road.com/chevy/mm-np203/>read the article</a>

    I would just stuff the shifter in 4 hi every once in a while, it will do the same thing as locking the hubs but you wouldnt have to get out of your truck

    formerly 77chev
     

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