I just had the LS7 rebuilt in my C5 and had a Monster stage 2 clutch installed at the same time with the Monster flywheel. Since getting the car back I have a driveline vibration that was never there before. The vibration seems to start around 2200 rpm and can be felt while driving in gear, when in neutral with the clutch engaged, and in neutral when the clutch is disengaged.

I have a bad feeling that the clutch or flywheel may not be balanced properly. Anyone have experience with this kind of problem? Will it hurt anything if I drive it like that?

 

Since you have a non stock engine, the hot balance related "match balancing" doesn't apply to you. Since you have an engine that was hand built, it's rotating assembly balance is hopefully better than stock. So you should be needing a clutch assembly that is as close to zero balanced as you can get. The aftermarket flywheel/pressure plate come zero balanced, but they are still only balanced to within certain balance tolerances. C5/C6 manual corvettes are extremely sensitive to very small imbalances, so it's possible you would have needed to have had the FW/PP checked and balanced eve closer to zero.
However, how can you know it's the new clutch? You had your whole engine rebuilt. New rotating assembly? Removed and replaced, did they check motor mounts, things of that nature. You changed a lot of things at one time, not just the clutch. The easiest thing to check now, however, is probably the clutch balance.
Have you contacted Monster? I would think they would tell you the same thing.
What all did you have done during this engine rebuild and clutch replacement?

 

Took the car by the shop that did the work. They think that it is a clutch and/or flywheel is slightly out of balance. The vibration isn't horrible but it is there. The car goes in on 10/20 to pull the clutch and check the balance. The engine (a non-stock LS7) was completely rebuilt using the existing Eagle crank/rods, new Ross pistons, new rings, new bearings, new cam, new lifters, new rocker arms, and new heads. The rotating assembly was rebalanced before the engine was reassembled. After assembly the engine was broken in on an engine dyno before being crated and shipped.

I'll contact Monster if it turns out that there is a problem with the clutch. I won't bother them now since I don't have all of the facts.

 

Absolutely keep us up to date, if there is an issue please let us know so we can get things taken care of. Feel free to give us a call if you have any questions.

 

Thanks. I'll let you know what the outcome is and will call if they are any questions or issues.

 

@thbwlZ, here we go agin! Can someone make some of your posts a sticky? I mean common. clutch vibration issues are more common than people would like to think.

 

I just want to be clear that I was not accusing Monster of having a faulty product. I don't have all of the facts yet. I was merely asking a question.

 

You're fine, I don't think it came across as accusatory towards Monster. I want to be clear that I am not criticizing them or their product either.

The problem is that C5/C6 manual vettes are extremely sensitive to very small imbalances, imbalances that would normally be fine for the engine but can result in unwanted vibrations. So even though Monster's flywheels and pressure plates, and any aftermarket vendor's for that matter, can be within a manufacturer's balance tolerance specification, they can still be slightly out enough, when combined with any small engine imbalances, to result in some vibrations. This isn't a criticism of Monster. GM gets the TOTAL engine balance, with flywheel and pressure plate mounted to the engine, down to within 0.5oz∙in. When the STOCK flywheels and pressure plates are delivered, they alone can be over that amount when combined. Then put it on an engine that can very well be over that amount and you have vibrations. GM took care of this situation with their external hot balance procedure.

The hot balance doesn't apply to your situation since you have a hand built engine, but instead you would want to balance your FW/PP combo down to as close to zero as possible. Even if it measures out to be what would normally be considered close enough to zero. You are having it taken out, that's the bulk of the work. You'd be well served to balance it even further to zero, as close as the shop can reasonably do, with their normal balancing operations.

Do you happen to have a balance sheet or something that shows you what your rotating assembly ended up being balanced to?

To my knowledge, Monster seems to be the only clutch vendor to acknowledge the factory external hot balance procedure and the C5/C6's driveline sensitivities to very small imbalances. That's a step in the right direction.

 

for some reason there wasn't a build sheet was not included when they crated the engine. I asked for a copy yesterday.

 

Just a follow up this. It took a while to get my car back into the shop.

The Monster flywheel/clutch was replaced with a new stock LS7 flywheel/clutch and the vibration is gone. No other changes were made.

 

Good news on solution 7L I went thru a similar problem. You had so many changes @ the same time that it could have been an ugly nightmare chasing it down. My stroker had run previously never noticing any vibration before the clutch swap so it was easy identifying the culprit. Now to R/R the clutch in a C5.......not so easy.

Do you have any concern with the LS7 clutch holding up? Not sure of your power level & what you do with the car. I tried an LS7 clutch with unfavourable results with Hi rpm shifts.

 

My car puts 500/470 corrected to the tire. I think that the LS7 clutch will be fine. I live at high altitude, 7350 feet, so the reality of my situation is that the car puts way less to the tire at this altitude than what the corrected numbers indicate.

We checked the torque tube while it was apart and everything inside looked brand new.

 

Hard to breath up there Rule of thumb is about 3% per thousand feet of elevation power loss, that is significant @ your location. I'm around 1k elevation, mountains all around us but most of the highways are in the valley's.