Front 4WD Actuator has a mind of it's own

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by CGower, Jun 19, 2010.

  1. CGower

    CGower New Member

    I have a 99 GMC Sierra with over 200K miles. 4WD was working fine until the other day. it started binding in the front like I was in 4WD. I can push all the buttons and can hear everything makes the correct noise and there is a marked difference as you can tell in 4HI it binds more, in 4LO really binds(on dry pavement) but when 2HI it makes noise and the everything looks/sounds right. However, here is the thing. The front a Diff is locked still. I pulled the actuator and it was extended to lock the Diff. The button and light indicated that it was in 2HI. With the ignition on and the Actuator plugged in and pressing the buttons it works fine. However with the truck started it defaults to extended. You can press all the buttons you want, but the actuator remains extended. This is of course the reason that the Diff is locked. So, what is the culprit? In the cab 4 button Switch (I have read many a story about these going bad)? The Actuator itself? But why does it work with the ignition on but not started? Is there something else that is causing the problem?? I have tested the switch and the output reading when you select the different buttons are not that much different from those that I have seen elsewhere, but they are different. I am stumped. I can see the actuator work so it is not stuck or broken, it is doing what it is being told to do. I don't really want to pay out to replace the Actuator or the switch if something else is causing the problem. Any thoughts?? BTW- I am new to the forum, looks like lots of good information. I just finished the thread about what sounds like worn U-Joints and it turned out to be the shackles. I have that issue as well. Glad to have that answer.

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