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Discussion in 'Chevy Trucks' started by CGLC, Nov 22, 2008.

  1. CGLC

    CGLC Senior Member
    Messages: 100

    I have a 1998 gmc 2500 gas ing. push button 4x4. I noticed just recently that when I push the 4x4 sometimes it makes a (thud like a hammer hitting thick steel sound). Doesn’t do it all the time; usually just the first time you are engaging it .
  2. tom_mccauley

    tom_mccauley Senior Member
    Messages: 465

    I would say U joints in the front shaft.:drinkup:
  3. Indy

    Indy Senior Member
    Messages: 704

    or a bad bearing in the transfer box (that;s what got me) but I had a similar noise.......

    BB recommended changing the fluid, that's when I found a spun race......

    good luck
  4. CGLC

    CGLC Senior Member
    Messages: 100

    whats a spun race? should i not change the fluid?
  5. tattooedplower

    tattooedplower Member
    Messages: 31

    Mine made the same kind of sound and I replaced the front u joints and now it's gone. Cheap easy fix!!
  6. exmark1

    exmark1 PlowSite.com Addict
    Messages: 1,320

    I had a 1993 that did a similar thing and it ended up just being U joints as well... I would hope for that the other options sounds expensive!