Flywheel chatter?

I posted up after I had my clutch, pressure plate, LWFW, SS kit, trans mount and bushings installed. I was having an issue with whine and chatter coming from the transmission while decelerating at low RPMs are when accelerating under load below 2,100ish RPM. I know what sounds are coming from the SS kit and bushings, but I want to make sure I know what "flywheel chatter is."

 

When I accelerate from low RPMs, such as after shifting into second, or when accelerating after coasting at low RPMs, I get a chatter/shake that sounds like a machine gun on a tin roof. The sound goes away once I hit 2,200+ RPM. I'm assuming this is what is called "flywheel chatter?" I had the tech that did the job dirve my car and he said it was all normal. I just want to make sure this is flywheel chatter. I know a lot of people say chatter happens at idle, but I don't have any funny noises at idle really.

Wow... AFTER shifting into second? You mean it chatters like that when the clutch is all the way out IN GEAR?!?

 

2 things that happen with normal noise in aftermarket fw / clutch setup

 

A LWFW is not going to be dual mass and the single mass FW is not going to deaden the gear noise the way a big, heavy sound deadening heavy one will. Engineers are paid a LOT of money to deal with vibration, harmonics and noise with OEM clutch setups. This is not true the same way with aftermarket clutches.

 

Off throttle when you say you are experiencing "chatter" I experience a light, tinny, gravel noise that is the gear noise in the tranny. On throttle or under torque it is silent. FWIW my car is totally quiet with clutch all the way in, either in gear or out, rolling or not.

 

True chatter from a clutch setup is about rough engagement when letting out the clutch. Anyone who has driven an unsprung clutch setup can tell you that some clutches are very ON-OFF. My old drag honda either launched, bucked or stalled. Maybe a botched install?

Wow... AFTER shifting into second? You mean it chatters like that when the clutch is all the way out IN GEAR?!?

 

2 things that happen with normal noise in aftermarket fw / clutch setup

 

A LWFW is not going to be dual mass and the single mass FW is not going to deaden the gear noise the way a big, heavy sound deadening heavy one will. Engineers are paid a LOT of money to deal with vibration, harmonics and noise with OEM clutch setups. This is not true the same way with aftermarket clutches.

 

Off throttle when you say you are experiencing "chatter" I experience a light, tinny, gravel noise that is the gear noise in the tranny. On throttle or under torque it is silent. FWIW my car is totally quiet with clutch all the way in, either in gear or out, rolling or not.

 

True chatter from a clutch setup is about rough engagement when letting out the clutch. Anyone who has driven an unsprung clutch setup can tell you that some clutches are very ON-OFF. My old drag honda either launched, bucked or stalled. Maybe a botched install?

 

I definitely hear gear noise, but I wouldn't say it's tiny. It's definitely audible to most people. Music loud enough will cover it up no problem, haha.

 

If by "in" you mean all the way to the floor, than mine is quiet too. Mine makes noise when I'm all the way off the clutch and accelerating in gear below 2K RPM. The more I "bog" it, the more it'll make noise.

 

They're a very reputable Subaru performance shop, so I'd hope that's not the case. I brought it back in to have the tech look at it and he said it was normal. Is it possible the 6speed gearbox just has more NVH than the 5speed box?

Sounds like you have regular gearbox noise/tinny-clatter rather than CHATTER. You could always post a video or get a ride in another car with a similar setup. Thats probably the next step I would take to reassure myself it was typical. Good luck RJ, wish I could help you more bro.

Sounds normal - Lightened flywheels are generally a bad idea, so enjoy the "performance" and the noise

I have a Spec stg II with the DM flywheel. Never had any tranny NVH until I went to group N mounts.

 

Remember the more power and mods U have are usually a trade off in terms of noise/vibration quality. Can't have the best of both all the time.

Does anyone have any data around what the OEM flywheels weigh in the 5mt/6mt?

 

From what I can tell via google searching, the STI 6mt flywheel is around 19lbs and the WRX 5mt is around 24lbs.

 

If the Spec B with the 6mt weighs in similar to the STI flywheel then going to the ACT streetlight which weighs around 15lbs shouldn't be a huge difference. If it's closer to the 24lb range then I think going to a 15lb flywheel is too drastic a change.

Does anyone have any data around what the OEM flywheels weigh in the 5mt/6mt?

 

From what I can tell via google searching, the STI 6mt flywheel is around 19lbs and the WRX 5mt is around 24lbs.

 

If the Spec B with the 6mt weighs in similar to the STI flywheel then going to the ACT streetlight which weighs around 15lbs shouldn't be a huge difference. If it's closer to the 24lb range then I think going to a 15lb flywheel is too drastic a change.

When I did my research I believe someone weighed our SpecB 6MT flywheels at around 24lbs.

I experience a light, tinny, gravel noise that is the gear noise in the tranny. On throttle or under torque it is silent. FWIW my car is totally quiet with clutch all the way in, either in gear or out, rolling or not.

 

I get the same noise now that I have changed to the ACT HD and WRX fw setup, is this normal? Should I be concerned? I do get some chatter when pulling out from a stop if the revs aren't just right.

Your LWFW has less mass and your clutch has more clamping force. I don't know if you get what I am saying so if this is TMI sorry...

 

Less rotational inertia in the motor makes it easier to spin. That means when you BLIP the throttle with no load, the engine revs should climb much more quickly. They should also FALL much more quicky. Once you put this arrangement under load, the engine wants to stall more rapidly than it would with a heavier flywheel because it has less rotational inertia to overcome the weight of the car. Got that?

 

The clutch you replaced was probably well seated and worn and smooth like butter. The new clutch setup has more clamping force. When you let the clutch out with more clamping force it is hitting the FW "harder" than before and the FW is less able to force the car forward.

 

Smooth engagement is going to be a MUCH smaller area in the powerband than before.

 

Sounds normal - Lightened flywheels are generally a bad idea, so enjoy the "performance" and the noise

Just to follow up, I went with the ACT HDSS Clutch and Streetlight flywheel for an 04+ sti in my 08 Spec B. So far I'm not really noticing any new noises, though I am having a tough time driving it smoothly and have stalled it a couple of times now. I get a bit of shuddering coming out of first or going into 2nd sometimes and I'm hopeful that will start to go away as it breaks in. It does seem to be getting smoother..

 

Edit:

 

Also, the Spec B oem flywheel weighed in at 28-30lbs. Not sure what aftermarket clutches will work while retaining the OEM flywheel though.

08 Spec B uses a Sti Flywheel so any clutch pack that will work with that should work with yours. Those LWFWs are good in theory and for the performance junkie but for a guy that wants near normal operation with a better clutch pack I would have went with a different clutch pack and retained the stock Flywheel. I have a LGT clutch pack and flywheel in my 2008 2.5i and I love it although it is 10x heavier in feel than the stock 2.5i setup

It's not an STI flywheel. The oem STI flywheel is an 18-20lb unit. If you decide to use an STI clutch, you have to use an STI flywheel either oem or aftermarket. I'm not sure if the standard lineup of aftermarket LGT clutch works with the OEM Spec B flywheel or not.

Its normal, I have an act lwfw and something down there clatters like a bastard under decel.

Its normal, I have an act lwfw and something down there clatters like a bastard under decel.

 

Sounds normal - Lightened flywheels are generally a bad idea, so enjoy the "performance" and the noise

 

i'll second and third. I made the mistake of putting a street light flywheel in my car and hate it. Car revs to quick so you have to really be good with the gas to rev match and also when your upshifting to. Its a pain in the ass if your tired and dont want to put up with it.

i'll second and third. I made the mistake of putting a street light flywheel in my car and hate it. Car revs to quick so you have to really be good with the gas to rev match and also when your upshifting to. Its a pain in the ass if your tired and dont want to put up with it.

 

+1 - exact same situation. I'm going to go back to the stock, heavy, dual mass flywheel.

i'll second and third. I made the mistake of putting a street light flywheel in my car and hate it. Car revs to quick so you have to really be good with the gas to rev match and also when your upshifting to. Its a pain in the ass if your tired and dont want to put up with it.

 

+1 - exact same situation. I'm going to go back to the stock, heavy, dual mass flywheel.

 

+2 - I didn't really know what to do when I replaced my clutch. I knew I needed a different flywheel, but I didn't know how to pick the right one. It came down to an OEM STI flywheel or the ACT. The price on the ACT was so much more attractive, and I didn't realize it would have some chatter. Oh well, live an learn, right?

 

If I'm driving home late at night and I'm tired, I feel like a 16-year-old who just learned to drive stick. You need to be quick and precise about your shifts because of how quickly the revs fall off. It makes rev matching a breeze though (although I never had a problem with the factory unit.)

+2 - I didn't really know what to do when I replaced my clutch. I knew I needed a different flywheel, but I didn't know how to pick the right one. It came down to an OEM STI flywheel or the ACT. The price on the ACT was so much more attractive, and I didn't realize it would have some chatter. Oh well, live an learn, right?

 

If I'm driving home late at night and I'm tired, I feel like a 16-year-old who just learned to drive stick. You need to be quick and precise about your shifts because of how quickly the revs fall off. It makes rev matching a breeze though (although I never had a problem with the factory unit.)

 

Plus another.. I am mostly use to it now, but It's not as easy to drive as it was with the stock unit.

 

I knew I needed to get a new flywheel as well as there aren't many clutch options for the Spec B. I wish I had gone with a stock STI unit though and if I do the job again I will.

Want to hear LWFW noise? Replace ALL your mounts and bushings... WOW. It was gravel-y before. Now its a box-of-rocks

I am still not sure why you guys are even using a flywheel.

I was thinking about replacing it with a manhole cover.

I get the NVH ever since putting in the sti/group in trans mounts to smooth out the clutch engagement. While it worked beautifully, I hate the grindy noise, I am thinking about saving up and getting an OEM dual mass FW and clutch.

 

The clutch plate is $138, Disk $148, Flywheel $500!!!

 

That is why they are so expensive.

ok.. so this noise is normal for using a non stock flywheel. I have the 06+ wrx flywheel which is only about 6lbs lighter than the stock DM flywheel. My new found tranny gear noise is not really that loud, but where can I, and others put dynamat type stuff to deaden this noise?

FWIW, after I replaced the left rear wheel bearing, most (90%) of the driveline noise went away.

 

The car has had a LWFW since 72,000 miles. STI tranny mount since 3000 miles.

Want to hear LWFW noise? Replace ALL your mounts and bushings... WOW. It was gravel-y before. Now its a box-of-rocks

 

 

That's what I did! I replaced them all, its not all that bad, I mostly coast in neutral anyway, its worst when I am decelerating in gear, in 4th and 5th, tiny bit in 3rd not really noticable. I am wondering if wrapping the shift lever or putting extra padding under the shifter cover will help.