Since it's cold and wet and I have no garage, is it safe for me to cap off where the vacuum line goes to the transfer case so I can save my HVAC? I've definitely got fluid in the lines-I capped it yesterday and when I checked a couple of hours later for fluid I noticed there was still a vacuum. Does the transfer case rely on this to vent or will it vent anyway?

 

The transfer case has a vent, separate from the transfer case switch with the three vacuum lines on it



Not the best pic, I know, but you can see the vent at the very top, and then the transfer case switch kinda below it

 

So, upon further inspection, the vent on top, tees into one of the three lines from the tcase switch. So I'm guessing it's more like a PCV, than a straight up vent.

 

Today I'm going to pull that transfer case switch and make sure it's good. I replaced it over a year ago, but who knows? Maybe it was bad or dirt got into it. I do know when I pulled the plastic female piece it was wet with fluid. When I sucked on the line going to the diaphragm I could definitely hear it moving and it held vacuum also. I replaced both lines going to and from-just not the vent line and that thing is in terrible shape as it leaves my fingers pitch black. I'll go ahead and replace that while I'm under it and try to get some answers. I can manually pull in my diaphragm and it will travel free until the last 1/2" or so where more force is needed to get it locked in. Is that resistance normal since it's not moving or does it sound like my gear has blunted ends that won't allow it to pull in all the way? I can bottom out the diaphragm with my fingers. It's got to be that it's simply not getting enough vacuum to pull in.

 

Could someone please explain my findings...any input I'd greatly appreciate. Last Tuesday after opting out on replacing the TCC valve in the transmission (didn't buy a new filter or fluid) I decided to mess with the non-engaging 4x4 again. I jacked up the front right tire as I know this is the one that spins freely when not engaged. I then pulled out the TC vacuum switch that I found covered in tranny fluid and gave it a good cleaning. (The second one I've bought from O'Reillys. Guy at NAPA claimed to have worked in a GM shop for 30 years and said those switches were the problem 90% of the time and that the ones from O'Reillys and their parts in general are junk....yea I know, sales pitch but he knew what he was talking about as far as that 4x4 system goes.) I noticed even with the switch in closed position there was still air seeping out around the plastic top. However my transfer case isn't overflowing so I have no clue how it's getting sucked through that vacuum switch.
Anyway, after starting the engine and hitting the 4-Hi switch I could still spin the right tire, but felt resistance. Thinking maybe a sticking caliper I was relieved to see the front drive shaft turning with the right front tire. This tells me the axle is engaged, at least somewhat. Am I able to turn it in 'Park' because of the front differential? It's one of those problems where someone experienced with these problems could probably figure out with some troubleshooting.

 

So you saying its in 4x4 and in park, but when you turn the right front wheel the front driveshaft turns?
If that is the case, it sound like the front axle disconnect is connecting properly and the transfer case is not engaging in 4x4. The front driveshaft should not be able to turn in 4x4 and park.

Have you tried removing the transfer case motor and manually putting it in 4x4 to see if that makes a difference? You can put the transfer case in 4x4 manually with a pair of pliers after that motor is removed and everything should work as if the motor had turned it.

 

Just want to add while shift motor is off the transfer case unplug it do NOT activate the dash switch with the motor pluged in it will ruin it ....

 

Thanks! If it's the electrical motor where you have to remove the front shaft to replace it, yes I replaced that piece of the puzzle also. So great, the axle is indeed locking (why I get no flashing error codes on the 4x4 push buttons) it just isn't getting any power transferred to it. That explains why when I was stuck last winter the front wheels did nothing. Stripped gears? I need to look up exactly what that actuator is doing to understand the problem.

 

After reading a few articles, I'm going to pull the fuse on the 4x4 for at least 30 minutes to do a hard reset. I've read this has solved problems for some. Perhaps when I put the new encoder motor in it didn't fully go to the home position. Try the simply things first right?

 

As winter is getting closer I figured I'd reassess my non-functioning 4x4 today and found this problem: no light with '4hi' and when I try turning the front driveshaft I can feel slight resistance but it still turns and this is where my slight grinding noise is coming from. I put a new encoder motor on a couple of years ago-so must be a problem inside the transfer case. Has anyone else had this problem and what is needed to fix it? It feels like it's trying to engage-just not quite 'there' to fully engage. When I turn the front drive shaft I can feel the gears trying to mesh-just not enough. What causes this? Encoder off a little bit? Or do I have bigger problems inside the transfer case? Tomorrow I'm pulling the encoder and seeing what happens when I manually engage the t-case.