clutch clunk with car on but not off
05-30-2015, 01:13 AM
#1
Cruising
Thread Starter
clutch clunk with car on but not off
Bear with me as this is my first post...ever.
This question is regarding a 2009 Z06.
After our last Autocross I noticed a clunk in stop and go Denver traffic when releasing the clutch.
Sounded and felt like a lose differential. I isolated the issue to the clutch I thought so checked out the forum and as the fluid was dirty thought I'd change it using the Ranger method....Thanks Ranger.
Anyway, I removed the fluid, added new, remembered to put the cap back on, and pumped the clutch. I repeated several times. Just to make sure I was circulating the fluid I started the car and when I pressed and then released the clutch peddle the clunk was there (car was in neutral). I could hear it and lightly feel it, so thought it might be a linkage issue???
I turned the car off and continued to pump the clutch. On the first pump and release of the clutch the clunk happened. But only on the first release of the peddle, then no more clunk. That seemed weird so I tried to replicate and sure enough when pumping the clutch with the car off no clunk, but when the car is on there is, and one but only one release of the clutch after the car is off.
I've read posts on the switch, but wouldn't think one would be able to hear and feel a switch being activated or axle bolts if in nuetral. It doesn't seem right that it would be a differential if it happening when the car is in neutral as no torque. And linkage can't be right if that is mechanical as it should happen if car is on or off. I first noticed it in first gear most of time and a lesser clunk when shifting to second, but then changing the fluid found it when the car is running in neutral but not happening when the car is off and clutch is pumped.
Any suggestions or direction as to what to check next would be appreciated.
Thanks,
This question is regarding a 2009 Z06.
After our last Autocross I noticed a clunk in stop and go Denver traffic when releasing the clutch.
Sounded and felt like a lose differential. I isolated the issue to the clutch I thought so checked out the forum and as the fluid was dirty thought I'd change it using the Ranger method....Thanks Ranger.
Anyway, I removed the fluid, added new, remembered to put the cap back on, and pumped the clutch. I repeated several times. Just to make sure I was circulating the fluid I started the car and when I pressed and then released the clutch peddle the clunk was there (car was in neutral). I could hear it and lightly feel it, so thought it might be a linkage issue???
I turned the car off and continued to pump the clutch. On the first pump and release of the clutch the clunk happened. But only on the first release of the peddle, then no more clunk. That seemed weird so I tried to replicate and sure enough when pumping the clutch with the car off no clunk, but when the car is on there is, and one but only one release of the clutch after the car is off.
I've read posts on the switch, but wouldn't think one would be able to hear and feel a switch being activated or axle bolts if in nuetral. It doesn't seem right that it would be a differential if it happening when the car is in neutral as no torque. And linkage can't be right if that is mechanical as it should happen if car is on or off. I first noticed it in first gear most of time and a lesser clunk when shifting to second, but then changing the fluid found it when the car is running in neutral but not happening when the car is off and clutch is pumped.
Any suggestions or direction as to what to check next would be appreciated.
Thanks,
05-30-2015, 10:52 AM
#2
Drifting
I am no expert but I will give this a shot. Others can chime in and add or correct me. The clutch is hydraulic so there is no linkage, save a tube running from the clutch master cylinder down into the slave cylinder.
When you depress the clutch, the slave cylinder presses against the throwout bearing (between the slave cyl and the pressure plate fingers) which, via a roller bearing that allows the pressure plate to keep spinning, presses against fingers on the pressure plate to release the springs on the pressure plate and unsandwich the clutch from the flywheel.
I have seen the fingers wear on the pressure plate if the throwout bearing gets worn and stops spinning. However, in this case, I doubt that's it since you aren't complaining about hard shifts.
You could have a worn pilot bearing. This is what holds the front of the shaft in the middle of the flywheel. Or you could have a bad carrier bearing in the torque tube that is allowing stuff to move during the clutch release.
I am going to guess that you have a broken pressure plate spring. The clunk is the plate snapping into place as you release the clutch. That is a wild a-- guess though. I hope some others chime in here.
Good luck and keep us posted.
When you depress the clutch, the slave cylinder presses against the throwout bearing (between the slave cyl and the pressure plate fingers) which, via a roller bearing that allows the pressure plate to keep spinning, presses against fingers on the pressure plate to release the springs on the pressure plate and unsandwich the clutch from the flywheel.
I have seen the fingers wear on the pressure plate if the throwout bearing gets worn and stops spinning. However, in this case, I doubt that's it since you aren't complaining about hard shifts.
You could have a worn pilot bearing. This is what holds the front of the shaft in the middle of the flywheel. Or you could have a bad carrier bearing in the torque tube that is allowing stuff to move during the clutch release.
I am going to guess that you have a broken pressure plate spring. The clunk is the plate snapping into place as you release the clutch. That is a wild a-- guess though. I hope some others chime in here.
Good luck and keep us posted.
05-31-2015, 11:47 PM
#3
Cruising
Thread Starter
Thanks Unixcorn, A lot to digest and time to dig into some schematics so I can visualize.
I did run another small autocross today and did not notice it...but honestly not sure if I would have in that situation....a bit more focused on other things
.
As a newbie I do want to throw out a Big THANK YOU!!! to the Vette community on this site and am grateful there are some many cool people willing to help others.
I did run another small autocross today and did not notice it...but honestly not sure if I would have in that situation....a bit more focused on other things
. As a newbie I do want to throw out a Big THANK YOU!!! to the Vette community on this site and am grateful there are some many cool people willing to help others.