Hey everyone. Sometimes I would notice that the front axle is slow to disengage out of 4WD. I would notice that if I press the 2HI button (it shifts instantly, only rarely would it take more than 1-2 seconds after pushing the button for it to change modes or ranges) and then try to spin the front driveshaft, it would not move. I would then pull the passenger side headlight and notice that the actuator is still in it's 4x4 engaged position (about 1/4-1/2" - same as when it is in 4 wheel). Rarely, it won't lock in on the first try. Especially if the truck is in park with the parking brakes set. I always make sure the front wheels are perfectly straight and before I even consider pressing any of the buttons (I heard from an offroader that trying to put a truck in 4WD with the wheels turned with the truck moving at all will break something). I would have to move the truck about 10-20 feet straight ahead and back and try both of those again and then I would find that it finally disengaged completely.
This is confusing because when we bought the car in Nov. 2007, we found out that the front axle had a broken shift fork that destroyed most of the inside of the front axle. Over $700 to fix at the GMC dealer. Then the TCCM failed 2 weeks later which was another $400 bucks (ATC fuse was also blown and the dealer tried 2 10-amp fuses and they blew also. They even charged us for the blown fuses! Over 5 bucks each!). Then it failed a third time. But this time we found it was Mr. Goodwrench's error. A 10 amp fuse in the 20 amp ATC circuit. I replaced it with a 20 amp fuse (what it calls for) and never had another problem with it (This was late January 2008). Am I looking at the beginnings of another expensive repair?
The 4WD seems to work fine. I noticed that during the winter, if it was in 2HI on ice, the wheels would just spin, but in 4HI, no tire spinning at all. I even pulled a Dodge Ram van a few months ago with it in 4LO over snow and ice 30 feet. My wheels were spinning in 2HI at the time. None in 4LO.
Sometimes the only way I could drive in the snow or on ice was in 4HI or 4LO. I also tested it on pavement by putting it in 2HI, making a tight turn with no throttle at the end of a parking lot and repeating the same test in 4HI. In 2HI, I could turn the wheel all the way around and make a tight 180 degree turn to the right with no additional power at slow speed. In 4HI, I would not be able to turn the wheel 180 degrees before it starts to bind up. Any more, the truck just stops where it is and it won't complete the turn. I would have to back it up, put it in 2HI, move the truck a few feet and then complete the turn.
Now, I wasn't doing anything crazy with the 4 wheel on pavement. I know driving on pavement will destroy the drivetrain in no time. I don't do it unless I am testing it if I suspect something and it is slow and careful. I was moving so slow, the speedometer barely registered. Not even 3mph.

Thanks for any advice on this.

EDIT: The front axle actuator looks like it was replaced recently. The metal part is still shiny with no rust. There doesn't seem to be any tears in the rubber part of it. It seems to be fully "deflated" when the truck is in either 4 wheel mode, pulling the cable 1/4" to 1/2" an inch (my best guess) and fully "inflated" when the truck is in 2HI. There is rust all around it on other parts (especially the battery tray). Therefore logic suggests it was not the one that was installed from the factory? As far as I know, this WAS NOT replaced at the time the dealer rebuilt the front axle.

 

It did it again yesterday. Had to get the truck unstuck from mud. Spun all 4 wheels a couple rotations before the tires caught on and got out. When I went to put it in 2HI, the actuator seemed to "inflate" but the cable didn't go back in the 2HI position. It finally went back after driving the car forward and backward a couple times. Does this mean that I am looking at a possible future problem with the front axle? I REALLY do not want another shift fork breaking and destroying the axle.

 

pull the vac line off the accuator if it is pulling in 2wd the vac switch is bad in the t case super common issue and could have contributed to your other issues

 

The actuator seems to be working properly. It is the cable that is not retracting like it is supposed to. The actuator seems to be in the 2WD (inflated) position when it is in 2HI, but the cable seems to still be in the 4HI/LO position until I move the truck a bit. Would it be a good idea to spray some WD-40 on the cable when the truck is in 4WD or will that cause a problem?

 

Lube the cable up and work it a bit. It just sounds like a sticky cable.

 

Ok, when I go out to the truck later I will do that and cycle the 4WD to make sure the cable is moving smoothly. Thanks.

 

Ok, I did a bit of a test. I was not able to reproduce the problem, but it seems that the actuator is working correctly and the cable is moving properly (about 1/4"- 1/2"). When I pressed the buttons, the transfer case moved within a 1/2 a second. It was deflated like a water bottle with all the air sucked out of it when it was in 4WD and inflated when in 2WD. I posted some photos of the actuator/cable assembly. Hopefully they are clear enough to see. I also hit the cable with some WD-40 when it was in 4HI.
However, I tried driving it on dirt and gravel and it wasn't binding as I was expecting, but I noticed that the front tire tracks in the mud when I made the turns with the truck in 4WD looked weird, as if there was alot of sideways tire motion (I don't know how to describe it. It just seemed like it wasn't freewheeling). I took it on the road for a short distance and turned around (at 10 mph) and it was binding a bit when the wheels were turned. I then jacked it up on the left side and rotate the left front tire and I heard a bit of a "click" sound and then I was only able to rotate the left tire about 2 inches and 10 degrees and it moved the front driveshaft and gave alot of resistance at the end of the range of travel as I rotated the tire. It did the same on the right. I tried the same in the rear just as a comparison. Same thing. Is this front axle locking in properly? With all these tests I did, does it seem that the 4WD is working properly? If I go to the beach this weekend and take the truck on the beach, does it seem that it will work fine? Thanks for any advice.


P.S: How hard/expensive would it be to install a Posi-Lock system? Would I have to connect it at the differential?