I've just got into a brand old '99 4.0L Wrangler, and also my first Jeep. I'm excited.
I noticed something yesterday however. When I have the wheel cut 100% in either direction there's a metal on metal grinding noise that's coming from, what I think, is the drive shaft. It does this going forward and in reverse, and in both 2WD or 4WD. I had originally thought it was the wheels rubbing because it has 31x10.5 tires on there but I noticed yesterday it wasn't. I took a video to make it more clear. Here's the video