I found a place in Memphis that can balance the new LS7 clutch disc, flywheel and pressure plate as an assembly.
But I've been asked if the LS6 engine is internally balanced or externally balanced. If it's INTERNALLY balanced, this shop says no problem, they can do it. If the LS6 is EXTERNALLY balanced, this shop says that balancing the LS7 clutch assembly won't help.
Since I had no vibration whatsoever with the stock CTS-V clutch assembly, and I have the vibration in neutral at the same rpm AFTER installing the LS7 clutch, I'm thinking it has to be the flywheel (because the clutch disc and pressure plate don't turn in neutral while the engine is running). Correct?
So the LS6 must be internally balanced. Please confirm.
According to the 2005 Service Manual the engine is Externally Balanced and both the Harmonic Balancer and the Flywheel have weights installed as part of the overall balancing process. This would seem to explain why aftermarket flywheels can introduce vibration.
Thats just great news. NOT! I am planning to replace my clutch this weekend and hopefully reduce if not eliminate the vibration. Now I may actually increase the vibration by installing a new flywheel. Its so frustrating to hear the flywheel effects the balance and the damper pully which doesnt have a keyway and can be orientated in any position. Seems its just about impossible to balance this engine once it leaves the factory.
I know the damper has threaded plugs that you can take out and move around but seems that would be a long process of trial and error. Anyone ever done that?
Well having reported what the Service Manual says I am hoping Ewill or others will chime in and explain what it really means - as a practical matter. I think there may be "less here than meets the eye."
I say that because the number of reports of vibrations caused by new clutches is relatively small. Especially, if you look at the "othe forum" where those guys swap clutches and aftermarket harmonic balancers with the same frequency as oil changes. Although there are a few threads concerning vibration and clutches, a search reveals no substantail evidence that folks subjecting their cars to post-mod external balancing.
It is my guess (pure speculation) that these engines are primarily internally balanced and that the "external" balancing is a fine tuning process. If that turns out to be the case, having aftermarket clutches checked for balance would make some sense.
"Since I had no vibration whatsoever with the stock CTS-V clutch assembly, and I have the vibration in neutral at the same rpm AFTER installing the LS7 clutch, I'm thinking it has to be the flywheel (because the clutch disc and pressure plate don't turn in neutral while the engine is running). Correct?"
No, the whole assembly spins in neutral.
With the clutch pedal in the disc doesn't spin.
The pressure plate assembly is bolted to the flywheel.
There are three parts of the drivetrain that can move independently. The first is engine to clutch assembly. the second is clutch assembly to transmission assembly, the third is transmission through the output shaft to the rest of the drivetrain - all the way to the wheels.
so if your car is in neutral, with the clutch engaged (i.e. pedal not pushed), then the engine, pressure plate, clutch, and transmission are getting power. if your car is in neutral with the clutch disengaged (pedal pushed), then the pressure plate spins on the flywheel, but the clutch disc, and subsequently transmission, does not.
Almost everything Mystical Ice said it true but the clutch moves independent of the drivetrain only in Nuteral. maybe a easier way to understand it is like this. Your engine crank is attached to your flywheel and the pressure plate is bolted to that. So that whole assemble Minus the clutch spins with the same RPM as the engine all the time. Your transmission has a main shaft that runs long enough to hold your clutch in between the flywheel and the pressure plate. So when the pedal is out (ingaged) everything spins together. Press the pedal down and they move independent. The Flywheel and PP at the eninge RPM and the clutch at whatever speed the rear wheels and gear your in. Unless your in Nuteral and then the Transmission input shaft is spinning with the clutch at Engine speed and the output shaft is same as the driveshaft and wheels. So its not rotating at all if your stopped but that clutch is spinning if the car is moving. That is why you can push start a stick shift car. The wheels rotating will spin the clutch and engaging it turns the motor over. The clutch is the only separation between engine rotation and the wheels. Hope that makes it clear.
Can the vibration be dampened by balancing the clutch disc, flywheel and pressure plate as an assembly even if the LS6 is externally balanced? I'm having a hard time understanding why it matters if the engine is internally or externally balanced.
Internally balanced means that the internal rotating assembly (crank, rods, pistons) was balanced as unit. It also means that the flywheel and clutch were balanced independently; and that the harmonic balancer is independently balanced. You can replace the flywheel and clutch on an internally balanced engine without adding vibration as long as the replacement flywheel/clutch assembly is in balance. The same is true for the harmonic balancer.
Externally balanced, on the other hand, means that the entire rotating mass, including the internal rotating assembly, harmonic balancer, and flywheel/cltuch unit, was balanced as a single unit. This means that if you replace the flywheel/clutch unit you will create an out of balance condition unless you: (a) balance the replacement flywheel/clutch assembly to replicate whatever imbalance was particular to the old flywheel/clutch aseimbly; or (b) rebalance the entire rotating mass (engine, clutch, and harmonic balancer).
My drivetrain had a ~2000rpm vibration when it was stock. (Car sitting still, rev it up and you'd get a vibration.) Based on the comments of the tech @ Lindsay who always works on my car, that's common to most Vs. Installing the ATI Superdamper made that vibration go away.
Well I am not sure, which is why I was hoping someone else would know. If my guess/hope that the engine is primarily balanced internally (using weights on the crank) and that the external balancing feature is less significant you can reduce the vibration by having any replacement flywheel/clutch assembly as close to zero out of balance as practical. This would ensure that you are not creating a new imbalance condition with the replacement part.
If my guess/hope is wrong, and the reliance on external balancing is substantial, without some process to rebalance the whole thing, replacing the flywheel/clutch assembly becomes a game of Russian Roulette.
Which ATI damper did you use? I went to the ATI website and they have all kinds of elastomers and weights for the LS6 V.
Thanks,
Jack
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