I knew there were issues with the 04-06 systems? Mine is an 07
Heard a grinding noise (thought I had a rock stuck in the brakes) driving down the highway today so I pulled over. Right before I stopped it made a popping noise and went away. Visually checked over everything then drove away with no more noise. Few minutes of driving and I was wondering what it was so I decided to try and shift into 4hi and nothing. No dash light, wouldnt engage and no noise. So I started looking into the IWE issues, visually checking vacuum lines. I found this on the drivers side just above the inner fender.. looks like one of the lines coming off the front drivers hub. Anyone know where it goes? It looks like a clean cut, and no indication that something was attached to it so it may not be related but not sure.

 

The grinding noise you heard in the front of the truck might be an IWE partially engaged / disengaged. And yes, that can happen when you lose vacuum. (IWEs are held disengaged by vacuum.) So if that indeed is a disconnected vacuum line, you could have IWE problems. If memory serves me correctly, there is a check valve below the battery box in that vintage truck, so see if there's one there and it came off.

Now for more news. If you're not getting the 4x4 indicator lights (4Hi or 4Lo) on the dash, it's more than a vacuum leak. That means your Transfer Case is not shifting - and that's not a vacuum problem. Generally, that means you ESOF Motor is not moving the Shift Fork. Different problem.

I'd start with the vacuum issue and see if that changes anything. Then see if the ESOF Motor on the back of the TC is actuating. Sometimes a little "love tap" from a mallet will wake it up. Other times it needs to be replaced.

 

I know the IWE vacuum lines well, since I recently replaced all of them for the IWE's on my 2006.

That line you referenced is a vacuum vent line, it's supposed to be open like that. So that specific tube is not your problem. Recommend getting a vacuum gauge, and hooking directly to the tube at the IWE.

 

You can disengage the vacuum line from the intake and run safely. That should stop the grinding. The IWE will be engaged and CV shaft will turn while driving but the truck will not be in 4wd if the transfer case is not switched on.

I had a bad IWE in my 05 during the middle of winter (hunting season) once. I ran this way for a couple of months until I could diagnose the issue and replace the IWE in warmer weather.

 

Hoping I get a chance this weekend to look into it.

Yesterday I did manage to get the dash light to come on indicating 4wd but it did not engage. The grinding noise I heard was only briefly until I pulled over. I have not heard it since. Truck is in 2wd (did a quick burnout to see)

 

If the dash light(s) come on, your Transfer Case is shifting. (That's a good thing.) You most likely have an IWE problem. The most common issue is a bad Solenoid, followed by bad IWE(s). Vacuum lines are rarely the problem.

 

had same problem to, checked all the vacuum lines-put new solenoid in & still didn't work. found the problem,the 2 connectors that go into the solenoid,just below them there's another connector & it's plastic,that was split. all three connectors come as one piece,like a y,three for the solenoid & 1 to the check valve. replaced it($15.00),works great know!!