I have a 2000 TJ, that I recently bought. I purchased it in a big hurry because it was a great deal and I didn't want to loose it! I bought it so fast that I forgot to test the four wheel drive, so two days ago I tried it. Four wheel high and low seemed to work great, but after trying out the four wheel drive it now makes an obnoxious squealing noise when I drive faster than about 10 or 15 miles an hour. I can't tell if the noise is coming from a specific side or just underneath. My first thought was that a U joint could have gone bad, but there is no pattern to the noise like there would be with a bad U joint as the wheels turn. It never did this until after I tried the four wheel drive, so I'm wondering if it could have something to do with the transfer case?? Does anyone have any ideas or suggestions as to what the problem could be?? Any help would be greatly appreciated!!