Still trying to distinguish between noise and vibration: they are two different things. However, we can say this with conviction: if you don't feel vibration with the clutch pedal depressed or the transmission in neutral, then flywheel balance is not the problem. Flywheel balance causes a vibration you can feel at the same RPM regardless of whether the car is in gear or not.

#2 here sounds more like a possible transmission issue, or it might be the normal rattle noise that all ZF6s make when switching to a single-mass flywheel. My guess is the latter. It's something a lot of folks just aren't used to. There is a fix that involves shimming the idler or input shaft (I forget which). Bill Boudreax, aka the "ZF Doc," came up with this, I think.
#3 might be the pilot bearing. Not sure. Could be a bearing in the transmission.

 

Hi Matthew,

your advice on the flywheel not being out of balance as the issue makes sense and is aligned with what Bill responded kindly to when I enquired the same. I do hear chirping so I do think that is a different flywheel issue. He suggested trying to have the pressure plate balanced and if that did not work then I was kinda out of luck. I will paste his remarks below for everyone so he doesn’t get 10,000 questions of the same.

I am now just going to have a local 5-star rated tranny shop take a look in there and go from there. The guy today at that shop did tell me it is better to have a single kit (fw/clutch) whereas I have a Rhinopac fw and a LUK clutch. When Insaid they were different his eyes kinda lit up like that may be the culprit. Maybe I’ll go with the Carolina Clutch FW/Clutch set up with a shim for the rocks in neutral and spend the $. Merry Christmas.

from Mr. Bill
”Hi Chris,

The pull-to-release type clutch kit pressure plates are no longer neutral balanced by the manufacturer. Recent samples of pull-type pressure plates have been found to be 24 to 36 grams out of neutral balance. you will need to find a shop that is capable of neutral balancing just the pressure plate by itself and hope that the single mass external balance type flywheel's balance is close to the original dual mass flywheel's balance. I recall that the original dual mass flywheel was discarded by the shop which if the case, puts you in a situation of great desperation with little hope for recovery otherwise. See attachment for further details why externally balanced C4 Corvette engine applications vary from vehicle to vehicle thanks to GM's production line band-aid engine balance vibration problem fix. If your C4 ZF Corvette was one of the many production vehicles that required post-production additional balancing of the OEM DMF flywheel and If you don't have the original flywheel to match balance with the replacement dual mass or single mass flywheel, then you are pretty much screwed big time. I hope neutral balancing the pressure plate works for you because the next engine balance correction option will likely exceed 50% of the current vehicle value cost-wise to remove the motor, disassemble and rebalance lower rotating assembly with external balanced flywheel.

best regards
Bill Boudreau”

 

I completely get what Bill is saying. I think there's an excellent chance that just neutral-balancing the pressure plate you have and then verifying that the flywheel you have is balanced to the correct spec (I forget the spec) will fix things. I would also verify that the "pedestals" where the p/p bolts to the flywheel are uniform in height to the friction surface and within spec. Bill may have mentioned that to you.

I do not buy the shop's theory that the different sources for the flywheel and p/p is the problem. These days, I think all the new replacement p/p are made in the same factory in China, regardless of what brand is on the box; and the flywheel either fits or it doesn't. I would not spend more money on a new clutch kit: they are all the same.

 

Matthew, thank you thank you for the sound advice which I will follow. I think you just saved me $1k. I will repost any outcome here. Thanks again. Chris

 

so, local reputable transmission repair shop owner indicated he thinks the issue has more to do with the transmission than the flywheels or clutch. Based on the noise in 2nd, 3rd, not so much 4th, 5th and bad in 6th, he has never heard of a flywheel/clutch solving that issue. He does acknowledge the ticking in the flywheel. He said he could refer me to a shop that specializes in GM manuals (he normally does Euro/Asian). New vs Rebuild? He suggested that all new transmissions are not what they used to be, cheap finger scratch aluminum, etc. I am not ready to have the tranny rebuilt but if I do I will also look into balancing the fw/pp. Thank you.

 

It's pretty rare that ZF6 really fails at stock power levels, although I'm sure it could if it were seriously abused by a previous owner. I don't think you'd find any new ones to replace it with, so a rebuild (or buying a used/rebuilt replacement) would be the only option. In the tranny, my guess is that the shim kit might get rid of most of the noises you're hearing. And just to be clear, the noise isn't a failure/malfunction: it's normal for a ZF6 with a solid flywheel. Between that and having your current pressure plate zero-balanced and verifying the flywheel has the correct external balance, I think you'd solve the issues for a minimal outlay of cash. Good luck!

 

Thank you again! I am strongly considering the above and will post again if I do with the results.