Quote:
Originally Posted by 67gtospud
If it ONLY happens when the clutch is pressed it's most likely the throw out bearing not the pilot bushing
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I agree with what you are saying in principle, and your idea is what is normally the issue. However, in this case, it was a bad pilot bushing without question. The throw out bearing is pristine.
When you step on the clutch, the throw out bearing contacts the "fingers" of the pressure plate. But don't forget that while this is going on, the transmission input shaft ceases to turn. So, now you have a stationary input shaft while the crankshaft remains at engine speed. Because the pilot bushing is "part" of the crankshaft, the pilot bushing is spinning on a stationary input shaft. This is precisely the source of my noise. Steel on steel.
When you let off the clutch pedal, the input shaft spins in conjunction with the pilot bushing, so my noise would go away.