Take a look at your pulleys while you let the jeep idle, you may have a pulley that may not be seated all the way, like the crank pulley. You may try to pull it off and re seat it. Do you have multiple belts going to the alternator? I have A/C on mine and have two belts going from the crank, water pump, compressor, and alternator, and had a similar squeel. I just pulled one belt off at a time and drove it around the block to figure out which belt was squeeling. You may also try to hit up wal mart and get some belt dressing. It is somewhat sticky, so as it conditions the belt is makes it sticky to have more bite on the pulley.