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Np203 leaking

Discussion in 'Transmission & Transfer Case' started by rwljpl, Feb 10, 2020.

  1. rwljpl

    rwljpl Member

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    Rich
    Truck Year:
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    Truck Model:
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    I’ve got an np203 mated to a th350. The transfer case is leaking a good bit from the front. Last time I had it in 4hi, it had a hard time getting back into 2hi. I’m a novice with these t-cases. What do I need to do? Look at a rebuild? Can I troubleshoot it? What kind of $$ am I looking at? Thanks for any help.
     
  2. ali_c20

    ali_c20 Full Access Member

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    Truck Year:
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    350, 350
  3. 75gmck25

    75gmck25 Full Access Member

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    Are you sure you have an NP203?

    A stock system would have no 2WD position, so maybe you have a converted NP203? If its converted, have you made sure it is full of oil (it uses 10w30) and is run in 4WD periodically to allow the pump to keep the case lubricated properly?

    Bruce
     
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  4. rwljpl

    rwljpl Member

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    Thanks. Definitely a converted 203. Recently changed oil with 10w30. The guy I bought the truck from thought it was a 205 which means he probably had the wrong oil in it. That may have been the start of the problem. On the other hand, it’s been around since 1977 so maybe it’s just time....
     
  5. 75gmck25

    75gmck25 Full Access Member

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    The chain in a 203 can develop slack and get noisy, but I've never heard of one actually breaking. They seem to be very durable.

    My 203 shifter linkage seems fine, but based on several postings it seems that many folks have problems with getting it adjusted. I've run across several articles on the linkage adjustment.

    Another item that might affect the linkage is the settling of the cab due to old rubber bushings. When I replaced my cab bushings I found that my cab floor had been sitting right on top of the transfer case, which made all the T-case noise transfer to the cab. My TH350 linkage was also off and I couldn't start the truck in neutral, but the TH350 linkage came right back into position when I replaced the cab bushings and got the cab at the right height.

    Bruce
     
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  6. nabeshin

    nabeshin Member

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    Truck Year:
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    Truck Model:
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    Engine Size:
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    I put straight 30 weight non-detergent oil in my 203. Somewhere I had read that you didn't want detergent oil in there cause that type of oil would froth up from the chain and lead to lack of proper lubrication.
     
  7. AuroraGirl

    AuroraGirl Full Access Member

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    At the same time, non detergent oil tends to be... non additive, correct? You would want a chain oil in that case, which resists throwing off when chain is not submerged, as in a chainsaw or bicycle.. but no idea to the other qualities of the oils. If it calls for 10w30 im sure thats perfectly fine.
     
  8. Dooley

    Dooley Full Access Member

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    I have run a few part timed 203's well over 100k without issues of oiling.
    I always added a bit more oil to the transfer case as instructed by one of the kit manufacturers back in the day.
    It seems to have worked well.
    Also when looking for a better 203 for replacement for the earlier years part way through 1978 and all the 1979 units had a narrower 2" chain but with a steeper cog/tooth and gear angle to match.
    It seems that stopped the issue of a worn chain from easily skipping over teeth in high torque instances.

    A pic of the fill plug modification that allowed enough oil for splash lubrication.
    I still locked in 4H every now and then when not needed just to be sure.

    [​IMG]
     
  9. jcondo

    jcondo Junior Member

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    Truck Year:
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    Engine Size:
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    if its leaking from the adapter plate seal, there is an "o" ring and paper gasket between the case and the adapter plate. think I got mine for less then $5. but while you have it down id replace the shaft seal as well.
     

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