New Clutch/Flywheel chatter...help!

[joe603]

This is a question for our resident tech's (or anyone who knows)....

Why does an aftermarket flywheel/clutch chatter (judder) in a G35/350Z?

What in the design of the transmission makes so much noise?

Is there anything that can be done to stop the noise? (without using the OEM dual-mass flywheel) The research that I've done on chatter usually leads to something faulty in the clutch system.

I'm looking for technical knowledge, pics, anything that can help me understand why this thing chatters like a big rig truck. I only have 100 miles on the clutch, so hopefully it will go away after it brakes in.

[Sentientbydesign]

He thinks it's going to go away

You'll eventually learn to drive around the noise. Like for instance, if you rev up slightly at take off, you avoid most of the vibrating noise.

Keeping the RPMs above 2k will also prevent most of the noise.

My RPS has been hit and miss. There's no logic to this, but it seems to chatter more if I've feathered it versus when I'm driving with minimal slip.

[joe603]

Don't get me wrong...the performance is 100x better than OEM! The car just goes faster. If you want to launch off the line, hold on! This thing grips like crazy! It's only when you try and baby it that the noise and bucking is an issue.

But what exactly makes this noise? If I'm not on a hill and don't give it any gas, the car doesn't buck, but you hear the chatter. If I give it gas I don't hear chatter but it has a tendency to buck (not all the time...)

[Sentientbydesign]

Here's a nice crossectional view of a dual mass (not the Nissan one).



Also check out this youtube:

http://www.youtube.com/watch?v=YnaXB8q3uzQ

My understanding is that the spring inside the flywheel serves to dampen power stroke pulses as well as the "bucking" you get from quick solid engagement.

[C-Kwik]

Joe. The term chatter when referring to a clutch problem has been used more traditionally to describe a slip-grip-slip-grip feel in a clutch as you try to start moving the vehicle. The chattering noise typical of the 6MT is a different thing altogether. You've referred to it as a judder and noise so I'm not sure which is actually occuring for you.

Chatter you feel is typically a result of a hot spot or contaminated contact surface. However, its not untypical for performance clutches that have high coefficients of friction to have a tendency to chatter as they tend to resist slip a lot. I don't recall what clutch you went with, but I had a dual friction type of clutch on a previous car and it chattered through its entire life.

If its chatter you only hear when in nuetral, then the increased noise should be expected since you ditched the OE dual-mass flywheel. The noise you hear is the backlash between gear teeth. Generally speaking, bigger gears require more backlash to operate correctly. Bigger gears are generally used in applications that have higher torque loads as bigger gears are stronger. The Dual-Mass flywheel inherently reduces some of this noise as it will absorb some of the torsional vibration. A solid flywheel will transmit all of the tortional vibration to the clutch. If the clutch does not use a sprunbg hub, it will in turn, tranmit virtually all that torsional vibration into the gears. You don't hear the noise when moving as the gears are loded when moving so they won't be clacking back and forth with each other since the net torque will be greater in one direction. IUn nuetral, there is no load, so the gears can freely move back and forth within the backlash. You could try playging with different gear oils to reduce the noise, but ultimately, it will still be there.

[C-Kwik]

My understanding is that the spring inside the flywheel serves to dampen power stroke pulses as well as the "bucking" you get from quick solid engagement.

The spring inside a dual-mass flywheel and a clutch disc hub are relatively soft springs. They will likely completely max out under load. I doubt they do anything to reduce the bucking. Higher coefficient materials tend to cause bucking. Especially while trying to induce some amount of slip. Most clutches using non-organic materials lack the ability to use a marcel spring. Organic clutch discs have a thin wavy piece of metal between each half of the clutch disc. This marcel spring helps to make the contact pressure more gradual resulting in smoother engagement. I've seen this in every organic disc I've come into contact with. And the few non-organic clutches I've seen had no marcel. I'm not sure if there are any non-organic discs that use a marcel.

[Jacko3]

Joe603:

I agree 100% with C-kwiks comment. And, I agree with them from a driving perspective---my constant flogging of my car on the secret track confirms much of what C-Kwik has said.

The G-35 Coupe 6MT and the 350Z are track cars placed on the streets. Don't be deceived. The dual mass flywheel designed for both cars was an after-thought of design only for those interested in luxury. I do not beleive the original intention of the car was to be quiet and luxurious. So, the chatter is inherently a part and parcel of the car's original philosophy of design. I don't think it will go away. So, enjoy the car with the chatter---I think it will take some getting used to.

The eficiency of the gear box of the car when on my secret track or at high RPM shifting, is the best I have ever experienced of any car----marvellous, exhiliarating, and perfect. Nothing on that car was designed for low speeds and low RPM. The G-35 Coupe is king on high RPM and high loads---that is what you will typically find on a car designed for track use. So, again, i wouldn't be driving the car gently and at crusing speeds all the time with after-market clutch system---it hurts the car---G-35 Coupe loves to be flogged. But then, it costs money to flog the car. 100 miles is barely 1 hour worth of driving for me on a day I am heavily possessed by the excitement of the car.

In neutral, when starting up in the morning, with my OEM clutch system, I can hear the chatter until the car warms and the gear oil has fully circulated on the gears in the gear box. After that the car is relatively quite. Apparently, it would appear that the gear oil makes a difference in the chatter of the car. However, after 3 laps of intense driving on my secret track, the car is even more quite than a brand new car. Again, this suggests that the fluids and the materials used in making the G-35 Coupe require constant flogging in order to get it to function the way the manufacturers intended.

So, it begs the questions:

1. Why is the 6MT gear box of the G-35 more quiet and cooperative after a flogging session than when it is left standing to warm up in neutral?

2. Why does the gear shift perfectly and like butter after an intense driving session than when you drive it normally like a human being?

3. Why does my engine use relatively low proportion of gas at higher RPMs than when it is driven gently at lower RPMs? My car burns more gas under normal driving conditions than under WOT.

4. The suspension of the G-35 Coupe seems to make the car wear its tires almost at the same rate when you drive it in a spirited fashion versus when you drive it around normally--the difference between the two conditions isn't that great or significant (1,000 - 2,000) , at least to me, so why even bother driving the car gently and normally to begin with? I can clock 1,000 miles in 2 - 2.5 weeks.

Just my experience and 2 cents.

[joe603]

Chano, no slipping at all...the problem is only noise.

[C-Kwik]

You referred to bucking in another thread...

[joe603]

Sure, it bucks sometimes on startup...but I think thats due to the lighter flywheel and the intense grip of the new puck-style clutch.

I just don't get where the noise comes from.

[Sentientbydesign]

I go through all that trouble finding the youtube vid and picture (both first up on google search ) and you're still wondering why your flywheel makes that noise?

[joe603]

I go through all that trouble finding the youtube vid and picture (both first up on google search ) and you're still wondering why your flywheel makes that noise?

I saw that before you posted it...still doesn't explain why our drivetrain makes noise with an aftermarket flywheel/clutch.

[C-Kwik]

Sure, it bucks sometimes on startup...but I think thats due to the lighter flywheel and the intense grip of the new puck-style clutch.

I just don't get where the noise comes from.

I explained the cause of the noise above in pretty good detail.

Here's a link to a source that is more knowledgable than I. Scroll back up to page 43 and start where it is titled clicking and clacking. Its pretty much what I said, but with much greater detail.

http://books.google.com/books?...cad=0

Let me know if the link doesn't work for you.

[awdjdmtalon]

Is the noise always there? Is it there only while driving? Is it only there when trying to start off from a stop or acdel. from a very low rpm?

I think once you answer these questions we can help.

But I can tell you from experience, if you have an other then stock clutch disk (read high performance), then this noise is normal for the last question. C-Kwik explained it supurbly (sp)

[joe603]

Thanks Chano!

So from what I can gather from the book, the chatter noise is coming from the the transmission gears. The dual-mass flywheel must act as dampener.

Here are some things I've noticed:

- When the car starts up, it revs up to about 3k much quicker than OEM.

- If I depress the clutch pedal the noise stops.

- If I have the clutch engaged (pedal up), and gently put it into a gear the noise gets softer. If I push to hard the RPMs start to decrease.

- The chatter is worse when the car is warm.

So, it sounds like the gear oil has a lot to do with the noise. Would a heaver oil lessen the sound?

[Sentientbydesign]

The dual-mass flywheel must act as dampener.

Joe...I'm going to smack you You sound like Vivek!

My understanding is that the spring inside the flywheel serves to dampen power stroke pulses as well as the "bucking" you get from quick solid engagement.

[C-Kwik]

Thanks Chano!

So from what I can gather from the book, the chatter noise is coming from the the transmission gears. The dual-mass flywheel must act as dampener.

Yep. Basically.

[joe603]

lol!

sorry...you get the cred for that statement SBD

I guess I was just trying to understand it by saying (typing) it out loud.

[Sentientbydesign]

Maybe if my avatar was a cool ninja instead of a ferocious shih tzu everybody would listen to me more often

[joe603]

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

http://www.atiperformanceprodu...x.htm

[Sentientbydesign]

It is also important to note that while the large springs of a dual mass flywheel absorb some of the torsional impulses conveyed to the crankshaft, they are not harmonic dampers, and are only responsible for a small reduction in vibration.

Not sure if this answers your question at all, but realistically, you're just going to have to get used to it, or go back to the factory flywheel.

[SteveTheTech]

I've never really looked into the actual root cause of this, due to the difficulty of pin pointing the chatter. The combustion pulses are being transmitted straight through the transmission, when the clutch is engaged. The components in the transmission where designed to use a dual mass, so there is nothing designed to absorb and varying pulses.

A stage 4 for daily driving is overkill. Affordable but at what cost? Not trying to bum you out but adding and heavier/dampening crank pulley may not be the best idea. The VQ is picky with things like that.

[RED_DET]

If you are running a puck style disc, it will chatter, sorry no way around it. I have a puck disc in the se-r and it chatters like nobodies business.

[joe603]

If you are running a puck style disc, it will chatter, sorry no way around it. I have a puck disc in the se-r and it chatters like nobodies business.

No way I live with that Mike! The stage 4, puck-style clutch disk isn't causing the chatter problem (from what I can gather in these discussions); it's the use of a solid flywheel that transfers engine pulses.

A stage 4 for daily driving is overkill. Affordable but at what cost? Not trying to bum you out but adding and heavier/dampening crank pulley may not be the best idea. The VQ is picky with things like that.

Steve, what is the range for the oil weight in the transmission? Could a thicker oil help with the trans noise? What do you think of the crank pulley dampener? You said the VQ is picky...how so? What kind of OEM damper does the 05 G35 have? As far as the stage 4 comment, I can get used to the heaver clutch pedal, new engagement point, and the technique to start from a stop smooth. After all, the OEM clutch is a pain to get used to as well!

Not sure if this answers your question at all, but realistically, you're just going to have to get used to it, or go back to the factory flywheel.

That quote is saying that the dual-mass flywheel is not as effective as adding an aftermarket harmonic damper. Using an ATI harmonic damper would do more to smooth out the crankshaft pulses...which would in-turn help with the trans gear chatter...in theory

[Sentientbydesign]

That quote is saying that the dual-mass flywheel is not as effective as adding an aftermarket harmonic damper. Using an ATI harmonic damper would do more to smooth out the crankshaft pulses...which would in-turn help with the trans gear chatter...in theory

This is not necessarily true. You're assuming that the gear chatter is caused by harmonic pulsing. All the website was saying was that lightweight, non-dampened underdrive pulleys were horrible for a crank shaft. It didn't say that the damper was going to magically smooth out a pulsing torque source.

Is the wife giving you hell about it? I'm just a little surprised at how freaked out you seem about it.

[joe603]

It's just hard to have a luxury car that makes noise like a concrete truck.

[Sentientbydesign]

Technically, it's a sports coupe. I don't even think Infiniti used the word "luxury" in the description.

Did you honestly not know that the aftermarket flywheels would chatter? Learning to drive around the noise is something you adapt to and a different flywheel/clutch combo probably would have also helped.

Try revving to about 1200-1500 and feathering it on take off. Your pedal should get a lot more even once the pressure plate is broken in. That will allow for easier foot adjustments.

[tollboothwilley]

Infiniti is Nissans LUXURY line, not their SPORT line

[Sentientbydesign]

Infiniti is Nissans LUXURY line, not their SPORT line

The G20 was anything but luxury. The 2003 G35 came with fabric seats and optional everything (read- "not luxury"). There are quite a few people that would argue that Infiniti's line up has teetered on the luxury line for a while. The G has always pushed performance over luxury.

[joe603]

Ok, lets not get into an argument over semantics...For arguments sake, lets call the G35 a sporty luxury car.

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.

So the problem isn't the flywheel, its the transmission gears.

I probably should have waited to break-in the clutch before posting...but it really sounded like something was wrong. The dealership actually installed 2 new transmissions before talking to engineers who said the noise was due to a solid flywheel. (which is misleading because the noise is from the gears...the OEM flywheel masked it somewhat).

I'm still hopeful on the harmonic balancer idea....