Ok last week, you guys suggested that I look at the vaccum systems on my inop 4HI. I replaced the actuator(under the battery) and the Vac switch on the transfer case(top side). I had trouble keeping the cable connected to the actuator with the clip for some reason, but eventually I got it to hold. The vacum was always pulling the cable even when I did not have it in 4HI. I was able to get the truck to go into and out of 4WD fine over the weekend, then this morning it went into 4WD again. Then this evening I got stuck in my driveway(we had a foot of snow dumped on us saturday) and I hit the button and no front wheel action at all. Two of the lights on the 3 button switch on the dash are burnt out 2hi and 4lo but when i put the 4hi bulb in them they work. I am wondering now what else could be wrong. Someone told me that the vac. reserve is not connected to the truck, and that possibly the check valve is backwards in the routing... any other thoughts or ideas? I sure do appreciate all the help, at least I had 4WD for the storm last week, now I need to fix it again tomorrow for the snow we are going to get tomorrow afternoon and night....

Thanks again!

 

just a quick thought. have you reset the encoder motor by pulling the courtesy lamp fuse and putting it back in?

 

no didnt know that was connected. Ill try it

 

As a side note, I pulled the battery and tray out this morning to check to see if the cable was still connected to the actuator and it is, but there is no vacuum pulling the cable now. As I stated earlier, it was always pulling two days ago and would not allow the cable to slide back into 2WD.. I did replace the vac. switch on the transfer case as well, so now I am VERY lost. Is there an electrical switch on the front axle or do i need to replace the encoder motor on the transfer case? It's snowing outside to beat the band and this thing does not go very well in 2WD in the snow... HELP!

 

There are a multitude of posts concerning the 4wd systems on these trucks. I would start by looking at what has been posted in the Tech Article (DIY) section as a start.

Are you sure you reconnected the vacuum lines at the switch properly? Have you manually locked in the front axle to see if that allows for proper 4wd operation? This can be done by pulling on the cable to engage the front diff and then locking it in place with a vice grip. Try not to damage the end of the cable.

 

Is there a way to pull the cable from underneath the truck to engage the front diff to the axle? I cant reach the other end of the cable without taking the battery/tray out and I am at work and just want 4x4 on the way home. We also got dumped on today.
Thanks!

 

I checked too make sure that I installed the lines on the new switch properly, and I had it on wrong. I put it on right and now I have little to no vacuum to the actuator. I was able to pull the cable and engage the front wheels. I locked that in place with a pair of vice grips, and i have 4WD. I checked for codes in the TCCM and there were none. I dont know what else to look for. I also know that I am having issues with my position of the heater/AC(floor,defrost,panel) selector. I found the lines that come up from the T-case and they go to a 3T-connector over near the drivers side of the hood corner, then one goes across the motor to the acutator and one goes to a port on the motor(i assume the supply?) and another goes down into the passenger compartment. The black ball on the hood is not plugged into anything and there does not appear to be anywhere to plug it into

 

Your hoses sound correct. The one not connected to anything is the vent to atmosphere.

 

I dont think they are correct, the resevior is not connected to anything. I think that there is a line missing that goes to it, which would also mean there is a another t-fitting missing

 

The reservoir needs to be connected. If your HVAC is not working properly, you have a vacuum leak. I have posted diagrams before so you should be able to find them using the search function. I can't look them up right now as I am kind of pressed for time and have a lot of stuff to respond to.