Its not your clutch, its most likely just the syncros (you said it has almost 150,000 miles in that other thread) are finally going. You can try switching to a good fluid like redline MT90, but a rebuild/replacement are in your future :( If the clutch is "slipping" then it is going, as in you hit the gas and the rpms increase but the car doesn't really move, or if when you shift the rpms dont drop back down right away after you release the clutch pedal.