NP 203 & U-jiont Question

Discussion in 'Trucks and Trailers' started by Bungy, May 20, 2001.

  1. Bungy

    Bungy LawnSite Member
    from MN
    Messages: 16

    I have a 78 K20 with a TH400 and NP 203. I took the front driveshaft off to replace the trashed u-joints and the truck rolled back. (the garage door stopped it) The tranny was in park and T-case in H. I put it into drive to move it back forward but nothing, the motor just reved and the tranny or t-case mad a whining sound. I put the t-case in Hloc and was able to move it. Is this normal or is my 203 shot? Is it OK to drive like this untill I get new u-jionts in the front shaft?
    Also, the front shaft has a double u-joint on one end with what looks like a ball and socket in between. Is this replacable as the ball is flat on one side and really sloppy. Thanx for any info, Bungy
  2. Alan

    Alan Member
    Messages: 1,185

    The case is fine, with the front shaft removed it saw a total loss of traction on the front end and sent all the power there until you locked it, which sent half the torque to the rear driveshaft, as ti was supposed to.

    The double joint is (I think) called a Cardin joint and it is replaceable, although a bit of a pain as I remember.

    As for driving it without a front shaft in HiLoc, I think you can get away with that for a while with no problems, shouldn't be any different than driving on a snow covered road with the case locked up, at least from a mechanical viewpoint.
  3. beerandcope

    beerandcope LawnSite Member
    Messages: 36

    just a question: 1. if your truck is in 2wh high then isnt the weight on the back wheels any way??????? 2. did you put the driveshaft back in to move it or not??? 3. and which high did you put it in to move it????
  4. Mudbug44s

    Mudbug44s LawnSite Member
    Messages: 23

    Just to clear a few things up:

    The Np 203 Transfer case is a full time T case. It doesnt have a "2 HI" Position unless you convert it to part time. The transfer case uses a torque Biasing system. There are 5 positions on the shifter. 4 HI, 4 HI Lock, Neutral, 4 Low, 4 Low Lock. In 4 Hi and 4 Low the transfer case splits the torque to the front and rear axles equally untill one of the axles loses traction. Then it acts just like an open rear differental and sends all the available torque to the axle with the least ammount of traction. In 4 Hi Lock and 4 Low Lock it is "Locked" into delivering the torque equally front and rear.

    Without having the front driveshaft installed and the transfer case shifter in 4 Hi, it sent all the torque to the front output flange. Putting the shifter into LOCK allowed the truck to move without the driveshaft installed in the front.

    If you install manual lockout hubs on the front axle of a truck equiped with a NP 203 T case you will have to have the shifter in 4 Hi Lock in order to make it move with the hubs "Unlocked". The front driveshaft will still spin and so will one axleshaft (if the differental is an open one) but you will not be driving the front wheels.

    I hope this helps clear things up a little.


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