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Help in determining NP203 p\t kit

Discussion in 'Chevy Trucks' started by wyldman, Jan 23, 2001.

  1. wyldman

    wyldman Member
    Messages: 3,265

    I have a 77 GMC Jimmy with a NP203 transfer case.It has manual locking hubs,which look like they were factory.Even has a GM sticker regarding hub operation on the drivers sun visor.It has no shift pattern on the knob,but from what I can determine it has (from top),4L-LOC,4L,N,4H,and 4H-LOC.I have heard of part time conversion kits.I am just wondering what they consist of,how they are installed,and how to tell if it already has one.Thanks
  2. 4x4k20

    4x4k20 Member
    Messages: 72

    are you sure you have a 203case? is your trans. a manual or auto most manuals came with locking hubs but had 205 case you could have some swapped in parts on your jimmy the 205 case just has 3 postions 4hi nuetral and 4lo the 203 has 5 shifter postions 4hi 4hilock nuetral 4lo and 4lo lock.let me know what you find out.go to milemarker.com they sell part-time kits you should see what they are

    [Edited by 4x4k20 on 01-23-2001 at 07:41 PM]
  3. wyldman

    wyldman Member
    Messages: 3,265

    It is definatly a NP203.I know the truck had some parts swapped before I got it.It has a turbo 350 trans.I saw the kit on mile markers website,but what exactly does the kit do ??
  4. mike reeh

    mike reeh Senior Member
    Messages: 114

    To tell if you HAVE the kit installed, put the truck in 2hi or Hi-Loc (both the same position, pull the shifter all the way back, as FAR as it will go, then forward one click)

    now unlock the hubs.. if you can still drive the truck, you have a part-time kit installed. if it goes no where, you have a stock np203 full time case.

    interesting, about the sun visor sticker.. GMC Jimmy is just a blazer.. Ive never seen a blazer or jimmy with a 205 case stock. Not in '77 anyways. You're saying that the sticker tells you how to use the manual locking hubs, right? I dont think you could confuse it with the one about full time 4x4.

    the kit eliminates the differential in the np203.

    mike reeh
  5. wyldman

    wyldman Member
    Messages: 3,265

    Thank you for the excellent explanation.I must have a part time kit installed,because it does drive with the hubs unlocked in 4HI or 4HI-LOC.

    I know this truck was pieced together from several other parts trucks,so maybe the visors came out of a newer truck with part time 4WD.It is possible the transfer case did as well,but from what I understand,all NP203 were full time cases anyways.

    so with the part-time kit,i am assuming the shift pattern would now be as follows


    Would this be correct ??
  6. reallyrusty

    reallyrusty Member
    Messages: 71

    I have a 74 k 20 with the part time kit installed
    What you do is remove the spider gears in the case differential and put in a solid coupling.
    The 1973-74 case instalation is a little different in that there is a shim that need to be replaced from a later case or surface grind the original down.
    The drawback is that the kit is a little harded on the case because there is no oil be pumped up to the rear output bearing. I put in a really good synthetic oil and make sure i shift the case in once or twice a week to lube it.I have had it in two years now, and I love it. The truck gas mileage went up from 10 to 12.

    The shift pattern is 4low,2low, neutral, 2hi,4hi,

    hope this helps
  7. wyldman

    wyldman Member
    Messages: 3,265

    Thanks for the info,but we found out the hard way about the lube problems.The partime kit burned up,due to poor lubrication.Found some more info about the kit,which requires the installation of an elbow into the fill hole to raise the fluid level a little higher.Have since rebuilt the case,replaced the part-time kit,and am running synthetic oil as well.They also recommend to run the case in 4WD,every 100 miles to help pull more oil up into the top of the case using the chain.