1986 GMC 3/4 Ton 4WD Pickup Transfer Case Noise/Problem

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Dave1, Jul 16, 2002.

  1. Dave1

    Dave1 Registered Member

    Jan 4, 2002
    Likes Received:
    Winter Springs, (Central) Florida

    I have a 1986 GMC 3/4 ton 4WD pickup with what I think is a NP208 transfer case, T400 trans, 350 "M" series,
    that has developed a problem in the transfer case. I have been asking around and so far have not come up
    with a definite determination or fix so I will try to describe to you and maybe someone has had similar
    experience and can help with information.

    The problem started a while back and what happens is when driving down the highway in 2WD high range
    and when I go over a bump in the road that jars the truck a bit a spinning or rotating noise starts inside the
    transfer case. It sounds like something has started rotating and is either grinding or rubbing against
    something else inside there. If I reach down and pull back slightly on the 4WD shift lever in the floor, you can
    immediately hear the noise slow down then quit. I am guessing when I pull back on the shift lever, I am
    seperating whatever is rubbing or grinding. I had the fluid changed by a local mechanic and he said the fluid
    had some shavings in it.

    I took the truck the local trans repair shop that said he has much experience with GM transfer cases. He split
    the case, found/replaced worn shift forks and pads, reassembled. He said everything else looked good. I
    drove the truck home and shortly afterwards the noise happened again. I took it back to him, he re-opened
    the case a second time and said he could not find anything wrong, put it back together, told me to drive it
    until it got worse or broke, then bring it back to him.

    I have been driving it and it is definitely getting worse as the noise occurs more frequently, is getting louder,
    and lately pulling back on the 4WD shift lever does not cause the noise to stop. Now I have to pull off the
    side of the road and come to a complete stop, then drive off.

    If anyone has had similar experience and/or can provide some information as to what may be the problem and
    how to fix it, please email me directly to davisalf@aol.com

    Thanks, Dave

    David Ford
    Winter Springs, Fla.
    407 830-3662
    <font color="black"> </font color>
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

    Jul 23, 2000
    Likes Received:
    E-town baby!
    It sounds like it needs the linkage adjusted. It could be riding between 2 HI and 4 HI and what you hear is the synchro complaining. Most Haynes or Chiltons will have the adjustment procedure outlined for you...


Share This Page