Re: 4x4 not working question
When your jeep has the full time 4x4, then it has the NV 247 T-case. This T-case has a progressive coupler, which will transfer the torque partly to the front wheels when a speed difference between the front propeller shaft and rear propeller shaft exists. So when 4 Lo works ok, but 4 automatic not, most probably the progressive coupler is inoperative. Firstly check the fluid level and the fluid itself for eventually metal particles or other contamination.
When 4x4 doesn´t work in automatic nor 4 Lo, then there is something else wrong inside the T-case. It could be that the chain inside the T-case is broken or stretched too much that it left the sprocket. An other possibility is that a previous owner just removed the front propeller shaft due to problems with the joints, that is easy to see if its there or not.