Clutch Noise

I have a 1987 Camaro with a 305 TPI V-8, with a 5-speed manual transmission. I rebuilt the transmission, and installed a new clutch, pressure plate, throw out bearing, and had the fly wheel ground (which the machine shop said that it took very little material off to get clean-up). When we first got the car running when the car is moving in any gear (even in neutral) with the clutch peddle down, I get a rotary grinding noise (but only about 30% of the time). If I let the clutch pedal up the noise stops immedately. The transmission shift smooly, in all gear selection. I thought that I had gotten a bad throw out bearing, so we installed an other new throw out bearing, but I get the same noise. Is there something that could cause this noise inside the transmission?

See attached pictures of my IROC Camaro

Did you inspect the pilot bearing in the flywheel before you reinstalled it? The machine shop that ground it for you probably removed it before it was worked on. If they didn’t put a new pilot bearing back in (I believe they have needle bearings) then it could be the source of the noise. Don’t ask me how I know this.

Do you mean the pilot bearing in the back end of the crankshaft? I put a new one in during the first installation. I looked at that bearing and the end of the input shaft on the trans when we pulled the trans this time, and saw no uneven wear, and the bearing was still tight in the end of the crank. It is a World Class T5 trans, if that makes any difference. The car came originally with an automatic, and we changed it over with all GM parts.

hmmm … with the clutch pedal down the pressure plate should completely disengage the clutch disc, right, so, since the clutch disc is connected to the xmission input shaft, the input side of the xmission wouldn’t turn at all except as back-projected through the motion of the drive wheels. Which you could eliminate by puttingthe xmission in neutral. Maybe that is a good test to try. See if the noise stops if the car is rolling but in neutral. You could at least tell if the noise is comming from the clutch disc area or further back in the xmission, past the gear shifting mechanism.

I’ll drive the car today and see if I can get the noise to react to your suggestion. I drove the car about 30 miles last night and had no noise at anytime?

" When we first got the car running when the car is moving in any gear (even in neutral) with the clutch peddle down, I get a rotary grinding noise (but only about 30% of the time). If I let the clutch pedal up the noise stops immedately."

Does the car have to be in motion to have the noise, or will it do it at a standstill ??

If it will do this at a standstill, it’s most certainly throw-out or pilot bearing related.

Few cars use needle, ball or roller bearings for the pilot…They would be too easy to damage as the transmission was being installed… Chevy’s generally use bronze bushings for this application…

I can start the car in the garage, and before moving, I can push the clutch in and out and I don’t have any noise. The noise only happens when I have moved or moving the car. I did install a new bronze pilot bushing in the initial installation. Are there two different lengths of input shaft for the T5 transmissions? Although I am sure that this transmission came out of the same car as the bell housing, could there be a sistuation where the input shaft is not reaching the pilot bushing? Since this engine was originally an automatic transmission car, could the crankshaft be recessed to where the input shaft doesn’t reach the pilot bushing? I never measured the distance from the mounting surface of the transmission on the bell housing to the pilot bearing, and compaired it to the length of the input shaft on the transmission.

No noise at idle with clutch-in/clutch-out? Seems unlikely to be the release bearing. Or the pressure plate, that’s probably not involved either. More likely something with the clutch disc or xmission input shaft or the xmission itself. If the noise is there with the car moving and the xmission in a forward gear, but goes away with the xmission in neutral (and coasting), then maybe look for a problem in the clutch disc/xmission input shaft area.