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85 Chevy K20 4X4 question

Discussion in 'Chevy Trucks' started by dneiding, Jan 12, 2011.

  1. dneiding

    dneiding Member
    Messages: 36

    In the last few weeks my truck makes a clunking noise when in 4WD. The frequency of the clunk, clunk , clunk is the same frequency as the wheel speed so it seems to be wheel/front drive train related. I only hear it in 4WD.

    Well today, while plowing, it got louder and there one or two jarring clunks. At one point, it seemed as if the front wheels were locked up (I couldn't see of course being in the truck driving and all). The rear wheels where spinning and the front tires where just inching along. I took it out of FWD and it didn't get any better. So I got out and unlocked the front hubs and everything seemed fine.

    So where should I start. Does this sound like a hub issue, a front differential or maybe a transfer case? Any tips on trouble-shooting this kind of issue would be appreciated.

    One more thing, I unlocked the hubs one at a time and tried to finish backing up but it didn't free up until I unlocked both. Not sure if that helps or not.

    Thanks in advance,

  2. wild bill

    wild bill PlowSite.com Addict
    Messages: 1,239


    check the axel u-joints ,drop the dif cover kinda almost sounds like the spider gear center pin lock bolt broke and the center pin is sliding out.:salute:
  3. dneiding

    dneiding Member
    Messages: 36

    Thanks, I will take a look. Now I have replaced u-joints before (just cause they were old) but how do you tell if one is bad? Obviously if it has bearings falling out its bad but are there other things to look for in a bad u-joint?
  4. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

    if you dont find outside problem . pull the cover. if oil AND chunks come out you got problems.

    if you still cant tell for sure take pics and post up.

    lots of chevy info in my head for these old solid axle trucks.

    and got a web site for ya if you need parts or help in your area. lots of good guys on it. just for 73-87 chevys. www.ck5.com.

    we can get ya hooked up.

    oh ya if hubs unlocked and 2wd position on t-case then no problems at all ?

    seen a few of the 208 tcases blow up and make lots of noise and only move in 4 low .
  5. dneiding

    dneiding Member
    Messages: 36

    If the hubs are unlocked and the transfer case is in 2WD no noise, no problems.

    I didn't try anything with 4WD low...should I lock the hubs and put it in low 4WD and let you know?
  6. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

    you can run 4wd low or high with no hubs locked. this might also be a good test for you to try and pin point the problem.
  7. dneiding

    dneiding Member
    Messages: 36

    This evening I went out and drove up and down the road a bit to do a little more trouble shooting and here is what I found.
    - With the hubs UNLOCKED I could put the transfer case in 4 hi or low and there was no noise or clunking at all
    - With the hubs LOCKED when I put the transfer case in 4 hi or low there was a bit of noise while driving in a straight line
    - With the hubs LOCKED and the transfer case in 4 hi, if I turned either direction - look out, lots of noise, jarring clunks and seeming like the front wheels were locking up
    - With the hubs LOCKED and the transfer case in 2WD when turning I still got all kinds of noise and clunking. Unlock the hubs, inch forward and backward a few times and all noise went away and everything was perfect.

    So it seems hubs locked and turning is the kicker - 4WD or 2WD there is lots of noise, jerking and tire lock ups.

    Does this sound like differential?