When I shift my TJ (99, 5spd, 4.0) from first to second and second to third I have begun to get a slight high-pitched squeal just before I shift gears. It doesn't occur from 3rd to 4th or 4th to 5th. And it seems to go away entirely once I've driven it awhile. Serpentine belt adjustment? I initially thought it might be the throw out bearing, but I'm a bit confused because it begins prior to shifting. Any ideas would be appreciated. The jeep has 75,000 miles and pretty much stock right now.