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how do i replace an NP203 chain?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by sleeper_dave, Oct 15, 2002.

  1. sleeper_dave

    sleeper_dave Registered Member

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    I have an NP203 transfer case. I blew one up a while ago, put in a junkyard one recently, and now i have a noise. It's like a popping sound, or a clunk. It is definitely from the front driveline, and it only happens under load, in forward or reverse, hi or low, lock or not lock. It goes away when i unlock the front hubs and run it in lock (this one isn't converted yet). From what i can gather, it's probably the chain.

    So my question is, do i have to pull the transfer case out of the truck to change the chain? I can drop the transfer case and pull it apart, and figure out how to do it, but i really don't want to take it out of the truck again.

    Thanks

    Dave
     
  2. CooknwithGas

    CooknwithGas 1/2 ton status

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    I recently tore mine down and reassembled it. You have to completely take it apart to get to the chain. You should investigate this before removing it. There is an inspection plate for the gear box, and there is a big, round cover on the back of the tcase you could remove to see if the chain is damaged. This round cover holds the bearings to the chain drive gear, so carefully remove it. There are many (over 150) bearings you will have to capture and re-install if you intend to take the t-case apart. I managed to find all of mine and put them all back in with the help of a little grease.

    If you have the time, I would just pull it and dissassemble the t-case. You will find any problems right away. It is pretty stout and any broken parts should be obvious. You can get a seal kit for about $20 to replace all gaskets and seals.

    PM me if you have any specific questions about the process.
     
  3. imiceman44

    imiceman44 1 ton status

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    Before you tear it up check your front CV joint, it would have the same symptoms and you did say you felt the vibes and noise from the front drive line.
     
  4. tipoil

    tipoil 1/2 ton status

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    maybe this will help a bit np 203 /forums/images/graemlins/thumb.gif
     
  5. sleeper_dave

    sleeper_dave Registered Member

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    i got that link by posting either here or on offroad.com, i don't recall. I went through all the NP203 stuff there, and saved it all to my computer, so i know that if i pull the transfer case i can defintely figure it out. But i already pulled and installed a transfer case once, and it was a dirty bitch from hell. I really, really don't want to do it again. I could do it, but i think this time i might really have to buy beer for my helpers. And that could get expensive. A day's worth of liquour for three college students? damn. well, it's cheaper than the 60$ an hour some greasemonkey would charge.

    And i checked the cv joint, it has very little or no play. I thought for a little while it might be the stops on the cv joint banging, so i ground them off and it didn't go away. So i'm pretty sure it's the chain.

    Thanks guys. any more info (such as a real easy, real cheap way to fix my problem /forums/images/graemlins/smirk.gif ) would be appreciated.

    dave
     
  6. 76_Cheyenne

    76_Cheyenne 1/2 ton status

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    Same thing happened to me, Check your CV joint and u-joints, I found one of my cv joint u-joint snap rings had come out and the whole u-joint started to slide out and it made sounds like a slapping or clunking/clicking. Take off your front driveshaft and check that out first, if you cant see anything visual, drive it without the fron driveshaft to see if the noise is still there, if it is then its the t-case, if not then its the CV joint.
    good luck, hopefully its your joint /forums/images/graemlins/pimp1.gif
     
  7. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    CV. Pull it and check it. You really cant tell it's screwed up in the truck.
    Typicaly a loose chain will only make noise under hard acceleration for a couple seconds till the truck gets moving. Fix the CV then you can test the chain. Put the truck in Low (not lock) get it on a steep hill and floor it. If the chain is loose you will get a couple of loud bangs as the chain jumps teeth.
     
  8. sleeper_dave

    sleeper_dave Registered Member

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    It doesn't make any noise if i unlock the front hubs and leave the transfer case in lock. Since i don't have the part-time conversion on this one, i have to leave it in lock to move if i unlock the hubs. So, when i do this, the front driveshaft is spinning but not under load (except the load from the inertia of the front axle), and there is no noise. When i lock the hubs back up and take the t-case out of lock, the noise comes back, but not when i'm just cruising, only when it's under load. The truck doesn't jump around, or feel like the chain is actually jumping teeth, but i do get the noise. I get it in high or low, but it's more pronounced in low (more load), and it only happens when i'm accelerating. I replaced the front driveshaft in the spring, and i've only off-roaded it a couple of times since then. I pulled the shaft and recently, and inspected it, i didn't see anything wrong with it.
     

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