Hello All,
I have an 02 Z and I have serious vibration issues from 2000-2300rpm and also neutral. Feel it throughout the whole car. Happened after a bad clutch install by a bad shop. New shop has replaced pilot bearing, slave, clutch unit was inspected and kept as it was a new unit from Mantic with only 100 miles on it, new torque tube splined shaft and couplers, just about everything is new except the middle and back shafts of the torque tube. Not sure what this could be but I'm guessing it has to be some other part or parts of the torque tube that are bad/bent. Or can a clutch unit become unbalanced from bad vibration? Need some help here please!! Thanks.
Kevin

 

I had a similar problem with a brand new aftermarket clutch/flywheel. Turned out that the clutch and/or flywheel were not correctly balanced.

 

 

There are a lot of stories about how a replacement C5 clutch has to be match balanced to the old clutch or else it will vibrate. The claim is that you must make sure to match balance the new to the old and install it in the same orientation.

On a similar note, some manufacturers like Monster have claimed here that 100's of their neutral balanced clutches are installed without any vibration complaints.

I have always has some doubts about the match balance claims. The reason why is that I have never seen any info on how badly the clutch was balanced before the match balancing which "fixed" the problem was performed. Actually, I kind of recall one story where the replacement clutch actually was out of balance a fair bit but the poster didn't want to take any chances so they had it match balanced. I have yet to see proof that a properly balanced clutch (neutral balanced) will cause vibrations like you are having.

Still, having posted the above, you could always try taking a few extra washers and putting them on different clutch pressure plate bolts in an attempt to lower the vibrations. Keep moving them around and trying different numbers until you get rid of the vibration. If you're not having any luck then it's likely something damaged and not just a simple clutch balance issue.

 

Do you have the old clutch? You would need it for match balancing. Otherwise, I remember someone taking their car into a specialty balancing facility and they balanced it on the car through the inspection cover as I recall.

 

The flywheel has to go back on just as it came off for balancing, from what I understand.

 

ZERO BALANCE isn't what it is cracked up to be!

EVERY MN6/MN12 C5 and or C6 goes through an ADDITIONAL (HOT BALANCE) procedure at the factory. The engine is fired up on PROPANE and the FLYWHEEL/ PRESSURE PLATE and the harmonic damper are adjusted to further balance the engine.

This procedure is accomplished to get rid of any drive train vibrations that are amplified by vehicles with clutches and torque tubes. The minor vibrations are not seen on automatic transmission vehicles.

SO,,, let’s say that your OEM "hot balanced" flywheel is now 10 Grams heavy in one spot to properly hot balance it.

After many years of FUN, your clutch and flywheel are shot and need replacement. SO,, you purchase that MAGIC "ZERO BALANCED" flywheel and install it.

Now your engine is 10 Grams out of balance and you magically have vibration issues.


The PROPER method would have been:

Match Mark the OEM OLD FLYWHEEL to where it was installed on the crank flange. Have the new zero balanced flywheel (OFF SET BALANCED) at the machine shop to mimic that 10 grams of factory hot balance that was induced at the factory.

The machine shop removes weight from the new flywheel so that it is 10 grams off set just like your old one was. Just make sure that you CLOCK the new fly wheel so that the weighted area is in the same place the OEM flywheel was. The machine shop SHOULD mark that for you. That should allow the engine to run vibration free.

Some people have been successful in TRANSFERING the old PINS that are in the old flywheel to the new OEM style flywheel (IF IT HAS HOLES for the pins in the outer ring). When you transfer pins, you have to ASSUME that the new flywheel is really ZERO BALANCED)

I hope this helps.

Bill

 

Some MN6/MN12 engines do not have any weighted pins in the flywheel and their owners just install that MAGIC new ZERO BALANCED flywheel right out of the box and everything works like new.

I was not that lucky as my 02 ZO6 old factory flywheel had ONE PIN installed.

I had the machine shop off set balance my new SPEC Flywheel to match the old flywheel. I installed the flywheel on the engine (without the drivetrain) and test ran it.

NO VIBRATIONS!

Some people say that the C5 Fly WHEEL is pinned to the crank. LOL! NOT!

It can be installed in as many ways as there are bolt holes in the flange! If you are lucky and forget to match mark it, sometimes you can match the RUST MARK pattern to see how the flywheel sat on the crank. There is a large hole for what looks like a place for an alignment pin and that isn't 100% guaranteed to always be lined up.

 

A cheep and relatively easy way to resolve the vibration problem would be to remove the lower inspection cover on the bell housing.

Mark each pressure plate bolt with a number. Add ONE metal washer to one of the pressure plate bolt locations and test run the engine in place through the noted vibration producing RPM. Note if the vibration gets worse or better.

If it gets worse, move the washer to another pressure plate bolt location. and test run the engine. Do that for all the pressure plate bolt locations.

If it gets better add additional washers to that area until you achieve the best results.

NOTE & CAUTION!! When you add washers to the pressure plate bolts, there may not be proper thread protrusion to allow the bolt to properly tighten and hold.

Once you figure out how many washers it takes to balance the engine, figure out the additional GRAMS the washers are and find a proper length fastener and adjust the washer weight with the longer fastener to match the required GRAMS it needs in that area.

 

I had the new clutch install now done by the Chevrolet dealership locally which has a special corvette department. Would they really miss checking something like that? They didn't express any concern of that type of issue. I'm not happy if that is the case. Granted they did not have the old unit in front of them but I would still they would have thought to check that when I brought it to them with vibration issues. Correct? Thanks.
Kevin

 

LOL!! You would be AMAZED at what " special corvette departments" dont know!!!

I dont know if you have any recourse but go ask them how they replace the fly wheel. Dont say anything about hot balance..

jBC

 

But what if the clutch tends to not be balanced well enough and the hot balancing is done to fine balance it?

As I posted before, I have yet to see a single confirmed case of a properly zero balanced clutch cause a vibration issue. I've only seen claims of the match balancing fixing a vibration on a clutch that was specified by the manufacturer as zero balanced but the zero balancing was NEVER confirmed.

It sounds like 7LitreC5 had a vibration issue and fixed it by getting the clutch properly zero balanced.

 

I know dealerships have a reputation around the country of being just part changers and not really analyzing the problem but the corvette department at the dealership I'm going to has gone above and beyond for me to help me out with this nightmare and have been really knowledgeable of everything I have discussed with them. I trust them with my car and if there was any liability of them missing something they would definitely help out. There suggestion was to replace it anyway with an LS7 clutch and OEM flywheel and said I was at risk with aftermarket. But if the issue is balancing the flywheel offset from zero in order to have the whole assembly be correct then I guess just changing one zero balanced unit for another would not of helped or will not help. I will give this feedback to them and see if they think there is any chance of this being the situation. Thanks everyone to has tried to help me resolve this issue and continues to try and help me. Much appreciated!!

 

Not sure if you have any service like this in Rochester: Link

 

 

Thanks Bill for the suggestion of the washer method. Shop said it would only take an hour or 2 to test and finally figure out if the clutch is my vibration issue. If it fixes the problem I will owe you a big favor. Thank you all for the input and helping me try to resolve this. I might end having to live with it if this doesn't work. If thats the case I may be trading in for a 2005 C6 with a supercharger on it that they have at the dealership there. My fiance is going to kill me!

 

:

She will get over it. I learned a lesson. I never telegraph my car buying intentions to a member of the fairer sex in advance. I just show up with my new toy and offer her a romantic date in it. That way, I only have to experience one outburst and listen to the " little boy" lecture once, and the deed is already done. This tactic doesn't, however, play too well in court at settlement time !

Dave

 

Forgiveness is much easier to get than permission.

 

PLEASE post up the results of the test be it negative or positive!!

If you can, take some pictures of the installed washers.

 

Sometimes you don't get either, but they get used to the idea eventually.