4x4 Problem - 93 Sonoma

[pstone11]

I've been having a weird problem with my daily driver 1993 GMC Sonoma 4x4 - 4.3L.. If I drive it for a while(20-30) minutes, then randomly on deceleration from speeds above 55 or so, it sounds like it tries to kick into 4x4, the front end gets loud (in neutral, or any gear) until I stop, then it makes a huge clunk, and then it's back to normal, drives fine. It might do this 2 or three times if I drive it for an hour or so..

Here's the sther stuff.. The light on my 4x4 console always shows the front end engaged no matter what - The 4x4 works fine in high and low, engages and disengages really easy. The 2H light will not come on after it's out of 4x4 all the other lights are out too.

I pulled the plunger out of the diff, and checked it - the ball bearing moves good, and when it's out, the console shows the front end disengaged, and when you push it in, it shows engaged. Then I checked the vacuum actuator under the battery tray, and it's always on, or sucked in. When I pull the vacuum line off of it, the actuator releases, and in turn the front end shows blank on the console. But I can't get the 2H light to come on, or that vacuum actuator to release on it's own..

So what controls all of this stuff?? There has to be one common solution for all of these problems. Dunno, I'm going to go back out and mess with it some more, Late

[pstone11]

It was the transfer case switch - It's a vacuum switch w/ three legs, 15 bucks - everything's working great now, for the moment anyways.... What a pain it was to change though...