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4wd clunk

Discussion in 'Chevy Trucks' started by jb1390, Oct 30, 2011.

  1. jb1390

    jb1390 Senior Member
    Messages: 710

    I have a clunk coming from a 2002 duramax with 149000 miles when in 4wd. The clunk sounds like a 2x4 snapping under the truck. U joints are fine, and it does not sound like cv's when i am standing outside the truck (coming from further underneath the vehicle).

    The truck has an allison 1000, and I believe a 263xhd transfer case.

    Does this sound like an internal problem-possibly a skipping chain?

    Is there any way of diagnosing this further (safely)?

    I can consistently get the noise when I hammer on the pedal, if I take it real easy, I can get it to act just fine. I cannot drive at high speed without the noise (tried tonight in the snow).

    I have done some reading on pump wear, etc. A rebuilt t-case (if that is what it is), runs about $1400. The parts are quite a bit cheaper, but I am not sure how easy of a job it is. Anyone with a similar issue want to chime in?
  2. carkey351

    carkey351 Senior Member
    Messages: 229

    If you can rebuild an automatic transmission, a T-case is similar in difficulty (easier in my opinion).
  3. jb1390

    jb1390 Senior Member
    Messages: 710

    I've never touched the inside of a tranny-always limited myself to motor/other vehicle stuff.

    If it's that tough, perhaps a rebuilt is the way to go.

    Any chance I missed something and this could be something other than the transfer case?
  4. kimber750

    kimber750 PlowSite Veteran
    Messages: 4,676

    No noise in 2wd? Going straight or turning? I would check everything noises can be hard to find, could sound like it is coming from the back when really it is the front. Had a noise on an old jeep I had every time I hit a bump. Sounded like it was coming from under drivers seat. Searched for years to find it, finally figured out it was one of the hood hinges. :blush2:
  5. jb1390

    jb1390 Senior Member
    Messages: 710

    No noise at all in 2wd.

    I had my wife drive it, while I stood outside, and the noise is not coming from the cv's.
    I repeated that test with a friend standing outside while I drove it. Same diagnosis.

    It does not matter if I am going straight or turning. The noise happens when it is under load. If I accelerate, it pops. If I drive slowly forward on dry pavement, eventually it pops. If I drive slowly on soft ground, sometimes it doesn't pop.

    I will drain the oil in the t-case as one more check.
  6. Triple L

    Triple L PlowSite Fanatic
    from Canada
    Messages: 6,078

    My rig was doing the same thing... Its not the trans, I have an ATS extreme in my truck, we've came to the conclusion that its coming from somewhere by the transfer case support crossmember... What it is I have no clue, My truck does it in 2wd, if I take off hard, crack, then stop nothing, but put it into reverse then it cracks... I almost think its a box mount or something but havent had the time to really dig into it... It seems to have stopped now all the suddon and I dont know why...
  7. BlizzardBeater

    BlizzardBeater Senior Member
    from Maine
    Messages: 420

    Just to to be a pain in the butt, I recommend you really take a look at the two U-joints on the axle driving the front differential. If you're absolutely positvie thats not it, check your tranny mount.
  8. kimber750

    kimber750 PlowSite Veteran
    Messages: 4,676

    X2 they may not be loose but bearing could be frozen and won't be long until a failure.
  9. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Do you have matching tires front and rear?
  10. jb1390

    jb1390 Senior Member
    Messages: 710

    So........I have a small hole in the side of the t-case. For anyone interested in reading more, check out 263xhd pump rub. Looking for a rebuilt case. Merchant automotive seems to be a decent price, and comes with a lifetime warranty against pump rub problems.