For my 4 wheel drive the vacuum shifter wont even move when u put it into either 4 high or 4 low. Any ideas what might be going on? My friend said it might be like the gear oil is low but idk how to check that and i cant find it!!! HEEELLPPPP!!!!

 

http://www.jeep4x4center.com/jeep-ax...herokee-xj.htm
here is an exploded view of ur front axle, part #18 is the vacuum motor now if ur trying to check your fluid u can remove the plu on the front cover of the dana 30 and stick ur finger in and see if theres fluid and if its clean if not u many want to pull the cover off to drain and then refill ur pig but if the motor isnt responding chances are u have a leak in ur vacuum line or the motor just isnt working

 

http://www.4x4xplor.com/diff-service.html
look at that if u have never changed diff fluid before

 

I just went through this with my 88 and it wasn't a hard task. First check to see if you have vaccum on the plastic lines, if you do check the medal ones, if there is vaccum there then you probably need a new diaphram but If there isn't anything from the plastic lines check the switch on the t-case. The medal lines on mine were clogged with corrosion and rust so I had to make new ones. The diaphram was kinda stuck to but I cleaned the fittings out with a parts cleaner and working the fork back and forth until it moved freely. If that doesn't work sorry.

 

is the diaphragm the hockey puck looking thing on the front axle?

 

I had similar trouble the other day, I ran a temporary vacuum line directly from the engine and connected directly to the where the yellow line was connected at the front axle, just leave the others off for now. and then I tested it and the 4x4 worked perfectly. I then found a vacuum line unplugged from a vacuum ball in the passenger side of my front bumper. After I reconnected that and put everything else back like it was then everything worked, even the light in the dash witch I HAD NEVER SEEN BEFORE.

 

Check to see if you have vacuum going to the end of the lines. Then if you do, you probably have a hole in the diaphragm, a common problem and you will just need to replace it.