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Old 09-23-2006, 11:52 PM   #1
caterpill
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Default Crude Transmission Deceleration and Acceleration Noise after Clutch/Flywheel Install

http://www.youtube.com/watch?v=f5Wo9DMlVRQ
^ Video of the noise. Can best be heard on video with the windows up.


Recently, i've done a clutch/flywheel job at school, and noticed that after the install, i've gotten a bad rattle noise that seems to be much worse then the original "subaru deceleration noise" that has been discussed to death.

For some background information, I have a slightly modified 2004 WRX(Catless UP, Down, Accessport Stage 2, Exhaust etc.) with 69,000 miles. Ever since about midway of owning the car since brand new, i've had the noisy in-gear deceleration as thousands of other subaru owners do. I recently changed the stock clutch with an OEM style Exedy replacement kit, and a 10lb Cusco Chromoly flywheel. The clutch kit included a new throwout bearing, pilot bearing, clutch disc, and pressure plate. Everything was torqued to spec, cleaned, and lubed according to the manual.

Now, I get a distinct, very loud rattling noise that occurs during in-gear off-throttle coast situations, somewhere above 1800rpm. The sound is loud enough to insist that there is a loost bolt sitting in a metal pan, vibrating away, yet there is none. I believe there is also a loud noise during acceleration, but it is hard to determine if it is an uppipe leak. For sure though, it seems that I must have done something to cause this noise.

I do remember having a little problem with seperating the engine and transmission bellhousing though, as I did the "move engine forward" method instead of dropping the transmission. Did I flex the input shaft too much while trying to pry the engine from the transmission? Could this be a possibility? I know a lightweight flywheel will cause more NVH but the noise is quite loud and obnoxious; it is very hard to ignore.

The best description I can come up with, is as if gears spinning in opposite directions were nipping each other loosely.

Could anyone give me some insight? I honestly wanted to brush it off but the noise bothers me; I just want to see if I could get any ideas..

Thank You In Advance.

EDIT: Added a video. A few things before watching. Don't mind my ghetto boost gauge bracket. And its hard to hold the camera steady. Also. My exhaust drowns out the noise so much that it sounds like a normal subaru deceleration noise! But I do know the difference and this is louder. Any thoughts? If it sounds normal, then I guess i'll live with it. :-D

Thanks!
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Last edited by caterpill; 09-24-2006 at 08:45 PM.
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Old 09-24-2006, 03:18 AM   #2
Rickyh
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I have the act streetlite flywheel and oem clutch and it is pretty loud off throttle. My wife actually gave the the "OMG WTF is that noise" the first time she heard it. It is normal. It sounds like all sorts of hell is going on.


I don't think you could have been rougher separating the tranny from the motor than I was. Slide hammer/5 pound maul/3 foot prybar.
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Old 09-24-2006, 07:51 AM   #3
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Are you sure? Haha, I mean, you're right about "all sorts of hell going on" but is it really this bad? If it's normal, then I think I can live with it, but it's kinda funny, my car sounds broke as I decelerate.

Anyhow, I dunno if you flexed the input shaft as much as I did. I think at one point in time the input shaft was not centered in the bearing retainer ("candlestick"?), there was so much pressure on it that it was closer to one side. As soon as the engine was seperated though, the input shaft seemed centered, and unharmed.. But I hope I didn't harm an internal bearing.

I think I will make a video tomorrow and see if I can post it up, just to make sure the sound is normal.

Thanks Again.
Dan
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Old 09-24-2006, 10:10 AM   #4
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A video would be cool. I would venture to say that it is normal. Mine sounds like a harsh grinding/popping/humming. Your flywheel is 4 pounds lighter than the one I have. I would guess that it would be even louder than my car because there is less mass to dampen any vibration.
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Old 09-24-2006, 11:45 AM   #5
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LW flywheel noise is normal I have it also with my Exedy Stage1 clutch and LWFW
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Old 09-25-2006, 10:05 AM   #6
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Added a video. Thoughts?
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Old 09-25-2006, 11:41 AM   #7
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I listened to your video. Sounds about right. Sounds like my car. I believe it is just normal noise. A bit disconcerting at first. Nothing to worry about.
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Old 09-25-2006, 12:54 PM   #8
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I have the exact same noise.... i have had it for 20 thousand miles with a ACT clutch and flywheel upgrade. If i hasnt hurt my car in 20 thousand miles its not going to hurt yours
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Old 11-27-2006, 10:13 AM   #9
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Yah, welcome to a lightened flywheel.
Check your wheel pressures, put them at the recommended 36f/32R, it will help a little.
It rattles because with a lightened flywheel you have a lot less inertia to keep everything meshed in the tranny. It seems like some of it is helped by replacing the various bushings which generally tightening up drivetrain.
The tranny/engine mounts, Rear Diff bushings, the tranny crossmember bushings, all seem to help some. Not to mention your entire drivetrain will feel better.
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Old 11-27-2006, 10:56 AM   #10
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yep get used to the noise man,lol, and even a lil shaking. but the spool is worth it to me. ive been running a spec stage2 and streetlite flywheeel on a ra gearbox and love it
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Old 11-27-2006, 12:59 PM   #11
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welcome to my world buddy, but yours is alot more raspy then mine

Exedy Stg1 upgraded from ACT clutch
LtFlw (13.9lbs)
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Old 11-27-2006, 02:35 PM   #12
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since it is lighter, it is thinner, and resonates more...that's normal..
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Old 11-28-2006, 07:07 PM   #13
Dan Cech
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I have a very similar noise in my legacy, I'm running a 13.8lb flywheel with a SPEC stg2+ clutch with the lightweight PP option.

Can't say how normal it is, I actually have a gearbox and diff from a 2.5RS I was going to swap in if it got any worse. Guess I'll just wait and see if it seems to be par for the course.
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Old 11-28-2006, 10:26 PM   #14
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My car makes a similar noise...sounds like something is really wrong with the car but my mechanic cant figure out why (thinks maybe a bearing) but told me not to worry about it.

Im running Exedy OEM and resurfaced fstock flywheel. Noise started about 5k miles after clutch install.

-Jeff
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Old 05-11-2007, 08:08 PM   #15
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I have this same problem with a Gruppe-S lightened flywheel and ACT street-strip clutch. I've searched around about this, but found nothing stating whether this is harmful over time to anything. I thought harmonics can cause damage over periods of time. Any input anyone?
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Old 05-11-2007, 08:27 PM   #16
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It is probably normal, but check your heat shield bolts just in case, they may have rattled loose.
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Old 05-11-2007, 11:40 PM   #17
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Sorry to go off topic, but gotta say, I love your exhaust! What is it?
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Old 05-12-2007, 10:57 AM   #18
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Quote:
Originally Posted by caterpill View Post
...10lb Cusco Chromoly flywheel...
Well, there's your problem right there! Not really a problem, but the newer USDM wrx gearboxes often sound like hell with a lightweight flywheel... and from what I've read it seems to get worse as the flywheel gets lighter. In fact, subaru was sometimes installing even heavier flywheels under warranty shortly after the US debut of the wrx to calm the decel noise and shudder folks where complaining about (My car's original owner told me that mine got it done a couple of years back). I've heard that noise in another wrx with a 12lb. flywheel before, sounds about right.
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Old 05-12-2007, 11:36 PM   #19
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Quote:
Originally Posted by Eluder View Post
Sorry to go off topic, but gotta say, I love your exhaust! What is it?

Hehe.. I hate to bump an old thread up since there are others similar to this and i've since found some resolution, but the exhaust is a HKS Carbon-Ti but it has no resonator and the internal "tuning tube" has been removed.
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Old 05-12-2007, 11:37 PM   #20
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Quote:
Originally Posted by jhargis View Post
Well, there's your problem right there! Not really a problem, but the newer USDM wrx gearboxes often sound like hell with a lightweight flywheel... and from what I've read it seems to get worse as the flywheel gets lighter. In fact, subaru was sometimes installing even heavier flywheels under warranty shortly after the US debut of the wrx to calm the decel noise and shudder folks where complaining about (My car's original owner told me that mine got it done a couple of years back). I've heard that noise in another wrx with a 12lb. flywheel before, sounds about right.
Thank You for the reply. I've since read up on this and found relief that it's no big thing to worry about
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Old 07-19-2007, 09:24 PM   #21
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Are there any lightened flywheels on the market that do not cause this horrendous noise on a bugeye model transmission? I have the Gruppe-S lightened flywheel with the Driveshaft Shop aluminum 1 piece driveshaft and the sound is horrible as well as the vibrations. When I get up to 100+ it feels like the whole car is going to shake apart.
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Old 07-19-2007, 10:10 PM   #22
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I have a ACT 12 lb flywheel and there is a lot of sound. I don't know if I would call it noise though.
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Old 07-20-2007, 11:24 AM   #23
karl750
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Mine comes and goes, but yours sounds normal. These flywheels suck for drag racing, but they make daily driving more fun....which is what i do daily
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Old 07-20-2007, 02:39 PM   #24
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As far as noise goes... nothing really out of the ordinary on mine. I have what I believe to be an STi 12.5lb. flywheel (at least that's what it looks like)... HOWEVER, I also have an STi vIII 5mt from 1996 with the older style case and 4.44FD, so it may have been built somewhat differently (I'm sure their manufacturing methods have changed at least somewhat between 1996 and 2002). I run valvolene 75w90 and 1qt. of pennzoil synchromesh. I did notice a lot more gear noise with Uncle Scotty's cocktail before switching back to valvolene/synchromesh, so I'm not sure if a different fluid may ease the noise a little bit.

They keep "refining" the 5mt... but based on my experience, I'd say they're going backwards. The older trans seems to be less noisey, less clunky on the shifting, and generally more well behaved than any of the newer suby 5mts that I've driven. I think it's just the way gear lash is set on the newer transmissions, plus maybe other manufacturing tolerances involved that cause the decel noise problem.
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Old 07-26-2007, 04:28 PM   #25
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does it sound like a kinda a grinding noise cause i just installed a 9lb flywheel with oem exedy clutch on my 03 wrx and after about 60 miles i notice a noise when decelerating
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