I tried going 4 wheeling yesterday but when I put my Jeep into 4WD when I start turning I can start to hear and feel crackling from the front end however when in 2WD this does not happen, would this be caused a bad U Joint on the front axle?

I have 262xxx km on it, when I went to get an oil change they told me my transmission fluid was low and transfer case fuel was bone dry so I paid to have them filled up, however filling up the transfer case didn't do anything.

 

You're not engaging 4WD on pavement, are you? That's bad for the transfer case, among other parts and can cause sounds like popping, at least from my attempts to do that before learning it was bad. 262K on the clock, so it's very possible a U-Joint is bad if they've never been changed or anything. Not a hard job to do, just a little time consuming.

As for the T-Case being as you said "bone dry", that may have caused damage inside it. I would assume a stretched chain could be one, maybe a bearing or two damaged. Of course, if it were a bearing, I'm sure you'd hear it all the time since I'm fairly sure all the bearings inside are always turning regardless of 4WD engagement. Someone correct me on that if I'm wrong