[ToySub1946]

Throw out bearing is actually in use (spinning, using it's bearings) when the clutch pedal is pressed. If the throw out bearing were bad, this is when you'd hear it.

And with the pedal depressed, clutch is released, and transmission input shaft should stop moving....so there would be less vibration going through the rear of the transmission, less vibration on transmission rear mounts and driveshaft, etc.

So answer: something else.