4x4 is not engaging. Indicator light was working when I bought the truck a few weeks ago.
Now I shift into 4x4 and no light on dash. I do have a small vacuum line that is not connected back where the cross member is right where the metal lines go to plastic. I do not feel any pressure at that point with transfer case in 4x4. Also the vacuum shift motor will rotate back and forth. Should that be tight?

 

Actuator is held in place by an E clip, inside the housing. If it rotates, thats ok. (mine was rusted solid...... was a real bear to get out.)

The disconnected vacuum line is more than likely your problem. There is no pressure on either line, only vacuum, and that depends on where your T-case shift lever is at.

Also, check the connector at the cad unit, it likes to leap off.

 

that line needs to be connected. simple. When shifted in 4x4 one vacuum line is activated. this forces the vacuum motor to slide the coupler over to lock in 4wd. in 2wd vacuum runs the other way sliding the coupler back. The vacuum motor moves freely because one of the lines is disconnected. if there is no vacuum it could be a stuck/faulty vacuum switch on top of the t-case. its 15 bucks and easy to replace/

 

here you go - the whole story.
http://dodgeram.org/tech/repair/4X4/4x4_engagment.htm