I don't use my 4 wheel drive much, but with approaching bad weather, decided to make sure it was working. First shifted into 4x4 ok, but then would not disengage. After backing up, letting it coast, etc. I decided to just drive about 35 mph and see what happened. About a mile later it made a clunk sound and disengaged. Now it won't engage at all. The indicator light showing the front drivetrain seems to be working fine. About a year ago I had no 4x4 and drivetrain light was not on. Turned out the vacuum line to front axle actuator was disconnected. I'm leaning toward a bad actuator now. Is there and steps I can take to diagnose the problem? I hate to spend $50 for an actuator and find out it wasn't that after all. Any help would be greatly appreciated. Thanks, Randy

 

A bad actuator would not cause the system to become stuck in 4wd. A frozen cable could cause the front axle to stay locked in, but that wouldn't keep the transfer case from shifting out of 4HI.

When you say that it will not disengage, what is it doing?

Also, do you have the electronic or manually shifted transfer case?

 

It's a manual shift transfer case. I tried a few things and now thinking it may be a bad cable like you say, or something broken in the differential. I notice a switch or sensor looking thing where cable connects to differential. I'm assuming this trips the light on the console diagram that shows front drivetrain engaged? It lights up but no front engagement. When I manually pull vacuum to actuator and hold it, it is holding vacuum ok, so I ruled out a bad diaphragm. Will this sensor light work if cable is stuck? Or maybe cable is working enough to trip sensor but not enough to engage differential? The whole clunk sound when it was stuck in 4wd and finally disengaged has me worried.

 

The cable might be moving enough to activate the switch, but not engage the front axle. How far is it moving?

You may have to pull off the passenger side extension tube to make sure that everything is proper inside.

 

With a little help from Autozone.com and an exploded view of axle downloaded off the web, I pulled the actuator cable housing off the axle. When vacuum is applied to actuator, the cable moves about 1.5" to 2". It looked like everything was fine there, plenty of strong pull on cable from actuator. Next I got all four tires off the ground, started vehicle, put it in gear with transfer case in 4x4. Then I slid underneath and manually moved the shifter fork shaft in and out. It moved about 3/4"-1" and felt like it was moving it's full travel, but the front wheels never engaged. It made no grinding noises, so I figure either the shifting fork has jumped out of it track or something inside has seized up.
So without the expertise to pull the axle output shaft apart, and no money to pay someone to do it, I guess I'm going the winter in 2 wheel drive. Maybe when roads get slick I will shift into 4x4 and maybe get lucky and it will engage. But with my luck it won't disengage at all next time.

 

Sounds like either a broken shift fork or collar inside the front axle.

Pulling the extension tube isn't really all that difficult.

 

Really? Here is what autozone.com is saying. I'm not into dropping ball joints or pulling axle shafts. If I thought I could do it by removing the two nuts holding the axle tube, I might try it. But is it that easy?
http://www.autozone.com/autozone/rep...00c1528003dc94

 

On a '92, I believe that the CV shafts are bolted on. If so, just unbolt the CV shaft and slide it out of the way. Then unbolt the passenger side extension tube from the frame and from the differential center section (after properly supporting the center section).

 

Let me see if I can tell if CV shafts are bolted on. I'm thinking not because I had a bad boot one time that the garage fixed for me when I had the lower ball joint replaced. They actually replaced the shaft with a rebuilt one that had new boots on it. If the shaft bolted on would the boot be able to be replaced without dropping ball joint?

 

I have vehicle in the shop right now. Axle is pulling out of differential on drivers side. My mechanic pushed it back in, and he said it snapped into place, but first time I used 4x4 it pulled out again when front end disengaged. Will post what problem is when it is diagnosed. It may help someone else.