New Clutch/Flywheel chatter...help!

[Sentientbydesign]

Quite a few vehicles have dual mass flywheels. Nissan designed out transmission with a dual mass for a reason. If we choose to disregard it, we have to deal with the consequences.

[C-Kwik]

So...the noise is from the crank spinning. Would a crank dampener help?

Not really. Depending on its moment of intertia and how much can be instantly transmitted back into the crank, it may reduce torsional vibration amplitude slightly, but its doubtful there will be any significant decrease in chatter. Keep in mind that these torsional damping devices primarily help reduce torsional vibration by isolating the input from the output somewhat. Whether through a spring or rubber isolators, energy from the vibrations are absorbed by these "springs. Thus, much of the relative back and forth motion is reduced on the output end of the damper. But the vibration in the crank still exists as there are still power pulses.

A harmonic damper on the pulley end won't be able to provide any of its torsional damping properties to the flywheel and anything attached to it as its on the opposite side of the motor.

Since it's a luxury sports car, it should not have this noise problem. A mechanical clutch has been around for decades...and most applications have solid flywheels. I get why Nissan chose to use a dual-mass flywheel (to compensate for a noisy transmission) but it seems like an afterthought from an engineering perspective.

Would you rather they have made the transmission's strength the afterthought? Since its likely that larger diameter gears are the cheapest way to make a transmission stronger, this noice is going to be inherent of its strength. And while this isn't to infer what the capabilities of the G's transmission is, the MKIV TT Supra 6MT has the exact same noise. Those trannies are virtually bulletproof.

[joe603]

I just spoke with some very smart people at Forged Performance...

First, they agree with Chano, the harmonic balancer will not help. They put these on built engines and with a solid flywheel, they still chatter.

Second, the level of noise varies from car to car. Some are really quiet and some just have noise (same flywheel/clutch combo). So it does not matter what brand clutch/flywheel you use, only if you use the solid lightweight flywheel (and even then the noise varies).

Third, thicker gear oil may help, but if the trans is damaged, you can run into warranty issues. However I could use their synthetic fluid (Motul) which may mask some of the gear noise.

[Sentientbydesign]

Just wanted to clarify something from my experience. The type/brand of flywheel can make a difference. I'm not arguing with what Forged Performance said, but am just comparing the inverse statement to the converse statement.

So this would imply that a given flywheel may or may not make lots of chatter on a G/Z transmission, but two different flywheels on the same transmission can definitely make a difference in the noise.

[C-Kwik]

Just wanted to clarify something from my experience. The type/brand of flywheel can make a difference. I'm not arguing with what Forged Performance said, but am just comparing the inverse statement to the converse statement.

So this would imply that a given flywheel may or may not make lots of chatter on a G/Z transmission, but two different flywheels on the same transmission can definitely make a difference in the noise.

I'd probably agree with that. But purely on the basis of mass/moment of inertia. A flywheel with a higher moment will require more force to change the speed. So the forces from the pistons and rods would be absorbed by the higher moment resulting in lower instantaneous changes in flywheel speeds (the torsional vibration). Of course as the dual-mass flywheel allows some gear chatter, I'd speculate it would take quite a heavy solid mass to match the stock flywheel's noise level on a given transmission. However, there could be a slight difference betwen flywheels of different mass. How much is unknown. For all I know, the differences could be negligible. This is a purely conceptual thought.

[Sentientbydesign]

I agree with the concept. I have also heard that lighter flywheels chatter more than heavier ones and I'm seeing that now with the RPS versus the JWT. The JWT was 3.5 lbs lighter, but also consistently louder.

[RED_DET]

When exactly are you experiencing the chatter. During normal "slip" launch, while car is idling in neutral? If I try to slip my clutch, it will chatter. Sometimes while idling it will chatter, pushing in the clutch and releasing it quickly will quiet it down sometimes. I have had 3 different aftermarket clutch setups and none of them chattered except the puck. Every puck clutch I have heard chatters. Bringing the rpm's up a bit more than normal will ease the chatter during launch or I will just release the clutch very quick. You will definitely will have to adjust your driving style.

[joe603]

The chatter I'm referring to is the noise the transmission makes while the car is idling while stopped with the clutch engaged (pedal up) and in neutral.

It does make a noise when the engine is being lugged...doesn't matter what speed, only the low RPMs.

I will say that she's still getting broken in. This morning it wasn't too bad. Either I'm getting used to the clutch or the engagement is getting smoother.

I'm going to try and use a different gear oil than OEM...that may quiet the gear chatter. Forged Performance said that they would check out the car to see if the noise is normal...just gotta make the trek to north Atlanta

Nate, what is the RPS flywheel weight?

[Sentientbydesign]

RPS is 17.5 lbs. Kinda made me sad because the JWT was just over 14, but if it means a quieter transmission, then I guess it's worth it.

Of the 6 times I've checked on the flywheel noise, it's only made noise twice. 2/3 quiet is better than 1/50 quiet (old flywheel).