I really need help with this one. I have a very disturbing vibration that seems to be generating from the engine @ 1,600 rpm again at 2,200 rpm again at 3600rpm. I can produce it sitting still and slowly bringing up the rpm to these levels. But of corse the vibration is greater under load.

The car performs perfectly. No loss in power, no smoke, good gas mileage, no overheating. Runs like a scalded dog! Could it be the clutch / flywheel area? My mechanic is stumped, the dealer hasn't a clue. My car is a 98 coupe with a procharger, headers, x-pipe, aluminum flywheel & ZO6 clutch. Running about 10 lbs. of boost. Removed the belt from the SC and the vibration is still there.

Please help!!!
I'm going nuts about this!

 

crank pulley tight? is it wobblie?

 

It wobbles a slight bit. I understand that it is not a balacer pulley, just a pulley. The balancing is internal ( that is my understanding).

Are you entering a logical guess or do you have some real world evdence that this has been the culprit in someone else's car? Dont get me wrong, I fully appreciate your interest and your willingness to help, I'm just looking for information and was just trying to get a bead on your diagnostic idea. However I did see that the pulley wobbles. Should it be perfectly straight?

 

it's externally balanced and yes,i've seen it before

 

Not sure but this may be like being a little bit pregnant. Don't think the puppy is supposed wobble at all.

Charlie

 

Thanks to all that participated in the troubleshooting process. I took the car to Rev-Extreme and the techicians inspected the car. The diagnosis was that the crankshaft pulley was wobbling and that is what was causing the vibration. Well, I spent over 700.00 to replace the pulley and the vibration was the same. I am fully aware that this can be a very difficult diagnosis however after the repair, I went to the front desk and told them that the issue was still at hand and what should I do next. I am not here to bash this shop. Yet after spending this amount of money, and not bitching them out for missing the diagnosis, I began asking for more help. I remember standing at the front counter asking a group of technicians and principals for help and recieved no response. Just a couple of guys shaking their heads saying much of nothing.

This is a horrible place to be when you need help and are desperate for it. I felt abandonded in my search for this help. Not one time was I asked if I was satisfied.

Being fully disgusted concerning this issue, I was at Advanced Performance Tires and Rims in Drew Park and began to ask if anyone could tell me what was going on? I was refered to Greg @ Anti-Venom. I called him and stated my case. Upon his inspection of my car the next day, he immediately told me that there was no way the pulley was the source of the vibration. He said the vibration was not being generated from the front of the motor but from the rear.

His diagnosis was that it was certainly being generated from the clutch region. The clutch was inspected and found to be a new ZO6 clutch with a Fidenza aluminum flywheel. What had happened is the prevoius owner either replaced the cluth himself or had this done, and standard thread bolts were used to secure the pressure plate to the flywheel. Metric threads are the required fastner. Subequently, all of the bolts had lossened and one had sheared off completely. The clutch was in great shape but the flywheel must be replaced.

I wish to thank Greg @ Anti-Venom for properly diagnosing this issue and spending the quality customer care time with me to solve this problem.

The moral here is buyer beware. Ask more questions and get several diagnostic opinions before wasting money.

P.S. I picked up the old pulley and took it to a machine shop to test the truness of the rotation and behold, it was within the tolerence of the manufacturer. Just be careful where you spend your money. This thread is meant to be a service to all Corvette owners and nothing more.

 

Don't feel to bad about the dampner/pulley getting replaced. If it had a noticable wobble then it did need to be replaced either way.

Mine had a wobble and caused a belt squeak that I ignored too long. When it failed it made a mess out of the front of the motor.

 

The "wobbling pulley" diagnosis as the source of the vibration was certainly faulty. Almost every stock C5 pulley wobbles to some degree, and these cars do not vibrate to an extent that you could ever feel from the drivers' seat.. If you want "perfect" you have to go aftermarket. It's too bad you didn't recv. the proper feedback here from the CF, could have saved you some $$.

 

It isn't because I didn't try. I just did not get much information from the technical post. Another thing that kind of chafes me is that the new pulley wasn't pinned. During this repair period Anti-Venom is going to pin the pulley as I am also having a new camshaft setup installed. I asked to have the pulley pined @ the other shop and was told it wasn't required. When I mentioned this to Greg he stated that he pin's them when he does heads and cam cars. But in my supercharged applicaton it was a definite requirement. I believe that I like my new advisor / techician a whole lot better.