At first I thought the sound i was hearing was my clutch fan squeeking or the a/c compressor but this noise subdues a great deal when you depress the clutch. I looked in my haynes and the only conclusion I can find is it's either the TOB or the release bearing. The noise is a warbling, gritty sounding noise that is most evident at highway speeds and pretty much stays constant until you push the clutch in. The car has a tremec 3550 and i don't know what the clutch is... probably stock. 90lx, H/C/I, mostly mild stuff. The sound is driving me batty! Any ideas?