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GT_Red 01-15-2013 07:43 AM

The great LWFW NVH deal
So it appears that most if us, when we changed our flywheels over to single mass or lighter have experienced "the box of rocks" effect. Now I know the tendency is to blame the flywheel because that's what happened after you changed it out, seems fairly obvious.

However, my noise began as a slight rattle or vibration, and it stayed that way for many months, but when i moved and drove cross country, the problem exacerbated and its very loud. I took it to a place to check it out and they put it on the lift with a driver to put it in gear and it is not from the flywheel, but the center differential inside the transmission.

The bearings are wearing out, which I believe is happening to many of us. However, can we reverse the noise issue by reverting back to OEM clutch/flywheel and oem bushings?

Has anyone reverted back to OEM and had the problem ho away?

cheeseburger 01-15-2013 07:56 AM

reverting back to OEM weight won't solve the vibration caused by the diff, but it will reduce some of the NVH caused by having a lwfw. Have you also checked stuff like the condition of the bushings/mounts? Wear of these items can cause different resonances

sheppo9 01-15-2013 03:18 PM

It's the transfer case bearings and/or gear back lash.
You've shifted the load on them.

There is a HUGE thread on NASIOC about this.

king_j 01-15-2013 08:43 PM

So a lwfw will wear these bearing out faster?
Or do some cars just have bad bearings?

GT_Red 01-16-2013 06:49 AM

Do you happen to have that link to Naisoc?

Given the observational evidence that most people complain about the issue following the installation of a LWFW, I am tending to believe that it is the problem, and therefore would suggest against installing these products, even though results vary. Some do not have issues at all, but do you want to risk it?

Max Capacity 01-16-2013 07:55 AM

FWIW, I have had all the bearings replaced in my tranny more than a couple of times. The noise stays the same ever since the Spec LWFW was installed at 72,000 miles.

3rd and 4th gear sound like a bucket of rocks on decell going down a hill.

Nolmers06LGT 01-16-2013 02:21 PM


Originally Posted by Max Capacity (Post 4248770)
FWIW, I have had all the bearings replaced in my tranny more than a couple of times. The noise stays the same ever since the Spec LWFW was installed at 72,000 miles.

3rd and 4th gear sound like a bucket of rocks on decell going down a hill.

My 3rd and 4th are the worst as well... though 2nd was the worst until I swapped to the BAC5.2 cocktail. Since changing fluids my trans has gotten much quieter. The decel noise is still there, just not as bad as before.

I can't imagine it would be cheap to replace the bearings in the trans.. Is it worth it to swap the bearings or just start saving for a 6mt swap??

GTTuner 01-16-2013 02:51 PM

I never had the noise when I first installed my single mass flywheel, but within 3000 miles I started getting a loud whine from the trans. I replaced the output shaft bearings in the center diff, they were spalled and worn. I don't think the clutch had anything to do with it....there is a TSB from Subaru about revised bearings for greater durability. The new bearings have twice the number of rollers the original ones had. Super easy job,do it with the trans right in the car in about 2 hours.

sheppo9 01-16-2013 04:40 PM


Originally Posted by king_j (Post 4248437)
So a lwfw will wear these bearing out faster?

Doubt it, my cars been making the noise for 3 years or so and there is no excess shavings etc when I drop the gearbox oil.


Originally Posted by GT_Red (Post 4248700)
Do you happen to have that link to Naisoc?
and - which was a bent arm or something.

But there are alot more than just those 3 on the first 3 pages in the Transmission section.

GT_Red 01-16-2013 07:28 PM

OK so the answer appears to be the OEM fly and clutch makes the noise go away. That is testimony from 4 members on NAISOC who had the noise, and upon reverting back to stock, noise went away, I will be doing this soon, as I do not see the benefit of the LWFW over stock in the first place, at least not worth the hassle this has caused.

My setup was a 2007 WRX flywheel and matching exedy clutch kit.

All kinds of people trying to diagnose, I think replacing the clutch is cheaper than a tranny rebuild and sounds a whole lot cheaper too, worth a try.

f1anatic 01-17-2013 05:10 AM

My first LWFW install at around 30,000 miles (2007) did indeed introduce NVH. At 70,000 (2010) I replaced the clutch and upon reinstall, the problem was largely cured. The parts were the same - the difference was made by the installer. The first time I took it to a local Performance Shop specializing in Subaru. The second time I took it to a dealership but also all supporting parts were replaced, including throw-out bearing; tranny mounts were replaced with either new and/or STI / Group N part(s). Therefore, the quality of the install might also be due to new/improved parts not just a more experienced hand.

My setup consists of an ACT Heavy Duty Clutch and ACT LWFW for the 06-07 WRX

GT_Red 01-18-2013 12:41 PM

Interesting, however you still have some noise and vibration correct?

m sprank 01-20-2013 01:20 PM

A true LWFW will almost always be accompanied by deceleration chatter. This is normal.

For OEM SMFW users there should be no decel chatter. Not unless it is very very cold and/or your gear oil needs a change (my experience).

Obviously bearing wear and internal component wear could/would also contribute to any noise.

GT_Red 01-21-2013 07:22 AM

I am planning to revert back to stock, complete OEM with extra-s gear oil. Sucks because it's so expensive but these cars hate anything you do to them, so I will remain stock all around with the exception of my catback. I am surprised I didn't get some kind of code for that on this car. Never had a car I loved and hated so much.

Thinking about selling soon if anyone is interested. Located in S. Florida

GTTuner 01-21-2013 08:00 AM

OEM WRX flywheel here, no decell noise what-so-ever.

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