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1999 Chevy k3500 4low disengages

Discussion in 'Chevy Trucks' started by Kcorey, Feb 5, 2014.

  1. Kcorey

    Kcorey Junior Member
    Messages: 19

    I have a 1999 Chevy k3500 and sometimes when in 4 low it will randomly disengage. If I stop pull shifter up into neutral then put back in 4 low it's fine until it happens again ( sometimes right away sometimes it doesn't disengage). Does this have the electronic actuator on differential? Could it be replaced with a posi lock cable? I do not see my year truck on there website. When in 4 high it is fine it never disengages out of 4 hi unless I manually disengage . Thanks
  2. Rusty Silence

    Rusty Silence Senior Member
    Messages: 140

    I ran into that problem on a 96 K3500. If I remember right I was told I needed to replace or rebuild the t-case. In my situation it fixed itself, it was popping out of four low when I first got the truck but it quit doing it and it never did it again, even when plowing. The truck had sat for a few years before I bought it so maybe that had something to do with it.
    Just google the problem.
  3. 98K3500

    98K3500 Member
    from WI
    Messages: 46

    If it's not the NBS, it should have the same "thermal actuator" that my '98 does.

    Call the folks from Posi-Lock to confirm.

    When mines goes (they all do eventually), it's the route I'm taking.

    As to your issue - If 4WD hi works, it's the not the actuator...

    It may be linkage related, as I'm betting lo-range is not used too much annually.

    I'd get under the truck and see if it appears to be binding, etc.

    Lots of PB Blaster or a similar product may free it up if that's the case.

    Good luck!
  4. mcwlandscaping

    mcwlandscaping 2000 Club Member
    Messages: 2,557

    I'm surprised your 98 has the old style actuator as the 97 that I used to have had the electric style....I thought they switched to the electric style around '96.

    Hi/Lo 4*4 operations are changed in the T-case only, the front is either in or out...in other words, there is no hi/lo change in the front end. So as long as your 4*4 HI is operating correctly, then the front actuator is not the problem.
  5. 98K3500

    98K3500 Member
    from WI
    Messages: 46

    It's either as simple as a linkage issue, or as deep as an internal t-case issue.

    Since it pops into and out of 4-lo, I'd check linkage.

    My 98's' actuator is electric. It heats a small gas cylinder, and the gas inside expands, locking in the front-end.
    That's why it takes a little longer to "kick-in" when it's colder out...