I'm in the market for a new flywheel and clutch for my '03 350Z. I'm probably going to end up with the JWT 14lb setup, but a little concerned about the noise/chatter a lightweight single mass flywheel can cause.

I noticed JWT also has a stock weight (26 lb) single mass flywheel. Is this only for people that want to retain the stock feel, or would the heavier single mass flywheel also be quieter then the 26lb?

When does the chatter/noise happen? When the clutch is engaged and spinning the transmission in neutral? When the clutch is disengaged? When the car is moving at low RPM?

Is the noise cause by the clutch disk rattling between the flywheel and clutch or extra vibrations entering the transmission? I've found examples of people saying both, but I've also read that a thicker gear oil can help so I'm assuming the noise is actually coming from the transmission, not the flywheel/clutch?

 

I just replaced the clutch assembly in my 2003 350z, and I had the same questions you ask here.

What I determined in my research is that this involves much more than simply weight. Here is a good reference:
Light weight clutch components

 

Answering your question directly (without all the tech stuff)…

The light weight flywheel will spin faster and more quickly. When it engages the pressure plate, you will have more initial slipping (depending upon engine RPM's), and then sudden grapping, resulting in “chattering.” That is the nature of a light weight flywheel. You notice the difference when you engage the clutch, especially when running up the engine. It is noisy and rough with a light flywheel.

 

The noise typically attributed to "flywheel chatter" on our platform is actually the transmission chattering, which is more isolated with a dual mass flywheel. A 350z with a stock DMF makes mostly the same chatter, you just hear it less. But if you pay attention it is still present even on a stock Z.

Changing the transmission viscosity is definitely not recommended solely for the sake of making it quieter.

 

And to answer your question a stock weight, single mass flywheel would chatter much less than say a 14lb JWT smf. But then whats the point anyway, unless you are boosted or something like that.

 

Let's clarify something first - the distinction between drivetrain "noise" and "chatter".

Noise is different from chatter in that it originates in the transmission. Such noise (and actually a physical tapping like "sensation") is usually only felt at idle, in neutral, clutch PEDAL out/clutch itself engaged. Like sitting at a stoplight with foot off pedal waiting for green. As soon as you touch the clutch pedal with anything more than your foot resting on it, such noise goes away or diminishes to the point of not noticing it. This is due to the clutch being disengaged (actually load "applied" to the input shaft, similar to putting your finger against a vibrating harmonic fork.)

Note that ALL 350Z transmissions are "noisy" vis a vis, say a Getrag or Tremec. (Almost zero noise.) Noise is due to loosely set gear lash, particularly on the input shaft. Not a bad thing, just an operating characteristic of the Nissan CD, EA, JK transmissions. You should also note that a JK-series transmission (as used in the HR Z33) and the EA (used in Z34 applications) are inherently "noisier" than the earlier CD transmission (350Z 2003-2006) - both of my Nismos sounded like small cement mixers at idle .

Chatter, on the other hand, is a physical feeling when engaging the clutch - a vibration of the entire clutch and flywheel assembly when torque is applied - and is exacerbated when using a light flywheel that, because of its diminished weight and lack of shock absorbing density is felt both through the pedal and the shifter (connected as it is to the transmission).

So, what's this all mean? In answering your initial questions:

- A heavier single mass flywheel (or DMF) will NOT produce as much clutch chatter when engaging it. This is one of the reasons why I prefer heavier flywheels like DMF or heavier SMF (said another way, this is why I dislike light flywheels - for the application). Add to that the other characteristics of a light flywheel in all aspects of actual operation, not just in acceleration mode: engine lugging at speed, requires more attention to detail in shifting smoothly (which I admit becomes second nature after getting used to it), excess engine braking on downshifts, and need to constantly feed more right pedal to keep the car moving at cruising speed. While others will take issue with this, its my personal preference and the reason I feel that the negatives (again, based on my preferences only) outweigh the single benefit of a faster revving engine. I feel road work (whether track or back roads or wherever) demands smoothness to go fast, not just revs. That said, I would not hesitate to run a lightweight on a track-use car.

Note that when choosing a clutch for an HR application (my kid's car), we went with the JWT HD clutch, nodular iron flywheel, and relatedly, the ZSP HD CSC. Wonderful setup for us. Increased pedal weight - a much welcomed improvement on any HR car - but still not nearly as heavy (relative) as my DE equipped cars, none of the bad stuff I mentioned above, and smoothness through the drivetrain.

- Insofar as transmission noise, a heavier flywheel won't necessarily do anything to quiet down the transmission because as stated, there's no interaction between the flywheel and transmission (per se) while idling at a stoplight. The transmission continues to be noisy on an independent basis from the clutch engagement hardware. Besides, once that pedal is dropped, no one is or should be paying attention to the transmission noise.

That should answer your questions hopefully - in a somewhat roundabout way. "The MicThousandWordWay"....

EDIT: guitman32 said it already but bears repeating: do NOT deviate from gear oil specs. You can and most likely will damage the box. You do not need higher vis unless you are tracking the car and even then, best to consult a gearbox expert before doing so.

 

Nice. Was definitely referring to chatter the noise. Shouldnt be getting engagement chatter on an regular style organic clutch.

 

You can on a unsprung hub, honestly a single flywheel will feel the best, that being said I wouldn't recommend one that is too light. Maybe only a few pounds lighter

 

I bought the Z1 clutch and Exedy lightweight flywheel several years ago when I was backing out of my driveway and my clutch bought it. The Exedy SMF for the DE weighs 19 pounds, and has minimal noise. Not all SMF's are in the 13-14 pound range, you can get the Exedy, or Z1 midweight (21 pounds) which has minimal noise as well. I can't hear much of anything over my cams now, but prior to the cams install, there was virtually no noise from the Exedy that I could hear in ordinary driving.

 

South Band has very good kits for 350z. No chatter noise with their FlyWheels.