Red C6 Z06

This is weird. Help me figure out what it is:

It doesn't happen all the time (but I haven't nailed down the exact conditions), but there are times when I shift (when it's quiet enough to hear it) that I hear a spooling down - a whirring noise - as I am shifting into the next gear (up). I wish I could describe it better. I can say that it doesn't just occur as I push in the clutch, but as I get the shifter into the next gear and I am letting the clutch out I hear it.

It usually is most evident in between 1st, 2nd and 3rd.

To me it almost sounds like an idler shaft in a transmission that is coming to rest after being used in a prior gear. I don't know enough about the Z06 transmission to say there even is such a shaft.

Any ideas?

whatcop?

I think throwout bearings do that but I am not 100% sure

ipmtim

I have developed the exact sound.
I can duplicate it while stopped with the clutch pedal in and revving the engine. It happens while the rpm's drop through about 3k.
I was thinking throwout bearings as well.
TIA
Tim


By the way I have 48k on the clock with original stock running gear.

OVG

Try turning off the AC and see if the sound goes away. There were a number of these posts last summer and replacing the AC compressors eliminated it. My 07Z does it only when the outside air temps are above 90.

golf925

Hello OVG,
I have a 07 Z and i have same noise with OP when i shift up with AC on.
So if AC compressor is the issue, why does it only make noise when i release the clutch?
Thanks,
James,

ipmtim

I'll try it with the AC off, might not get to it until tomorrow though.
One more variable to eliminate.
Tim

Joe C5

Interesting - sounds just like my car (I see a new compressor in my future ). Mine will do it also with the AC on winding down in 1st close to 1200 RPM. Turn off the AC and it goes away...

ipmtim

new compressor or new throwout bearings.
niether is a cheap fix.

Red C6 Z06

Thanks guys. The 90+ degrees could certainly a contribution (it's been 90+ almost the whole time since I've been hearing it). I'll try it with the AC off too. My guess is that the AC compressor is a lot cheaper repair than the throw-out bearing!

Luweegy

You've got that right.

OVG

I don't know the answer to that and, I'm purely guessing here so don't beat me up if you disagree, that when the compressor stops being driven by the belt (when you lift off the throttle to shift) there is enough play in the parts inside the compressor that they rattle around until they start being driven by the belt again. But again, I really don't know. I can't get mine to repeat the noise when I get to the dealer to save my life. I told the tech it looks like I'm going to have to wait for it to completely fail to get it fixed. I'm glad I bought an extended warranty from Ken Fichtner!!

ipmtim

Went for a cruise last night and its definitely the AC compressor.
But the question is will a replacement fail the same way?
Does the bearing give it up because of too many rpm's?
Thanks for the help.
Tim

Twil1ght

That's almost always the AC...