Strange Noise

[Alex Blair (RIP)]

Originally posted by Stewart Loy
Throw Out Bearing Noise

I am restoring a 1942 Chevrolet CMP GS truck. The original engine was replaced with a direct swap 261 – a 1962. When the engine was rebuilt, I put the old clutch, pressure plate and throw out bearing behind it. The whole unit dropped into place without a hitch.

The engine was a bit noisy until I got the lifters set up now it runs well.

The problem I have now is when the clutch is depressed it sounds like a bad bearing.

I have replaced the throw out bearing twice in the past 3 days. The first one made no difference, so I asked a mechanic friend about this. His reply was that it was not uncommon to get a bad one – so I swapped it again. The same noise when the clutch is depressed.

I have the transmission out now – the shafts all feel OK, little wear on the input shaft. The clutch fingers are all flat, and everything seems bolted up how it is supposed to be. The bushing in the back of the crankshaft is OK. But it still growls when the clutch is depressed.

Does anybody have any idea what the problem is, and how to fix it?

Thanks,


Stewart

Stew....

The pressure plate actuation fingers of a friction clutch are provided with means for noise attenuation by the application of acoustical materials, alteration of the mass of vibrating parts, or surface treatment of slipping parts either individually or collectively to prevent the generation of objectionable noise due to resonance and sympathetic vibrations that are initiated by the stick-slip phenomenon as the non-rotating clutch release bearing contacts the relatively rotating actuation fingers.


Those "Clutch fingers " as you call them are actually Pressure plate fingers and it sounds like "rust'..take a real close look for broken springs in the clutch disc and that the fiber is not separating from the plate..
Then give your pressure plate a good bath in the parts washer and blow it clean with air hose and clean dry it with a shot of brake cleaner..(Not the clutch disc)..but a shot of brake cleaner on it would dry out any oil on it and not damage it.

make sure there are no burrs or dings where your throw out bearing slides and it is travelling the full length..
Sounds like a throw out bearing still..but a spare throw out bearing wouldn't be out of order.
If you hear the noise when you push on the clutch pedal, it could be a faulty release bearing. This problem needs to be repaired before more serious damage occurs.
If you hear the noise when your foot is off the clutch and pushing the clutch in makes the noise stop, this probably a problem with the input shaft bearing in the transmission

Keep us informed.