Gearbox Chatter after installing lightweight flywheel

["Stephen J. Habakus" <shabakus@xxxxxxxxxxxxxxx>]

I have a 95 M3
A couple months ago, with only 36k miles on the car I needed a new clutch.
I purchased a lightweight flywheel from Turner Motorsports which was installed at the same time the dealer installed the new clutch.
After approximately 6 weeks of driving I noticed a "rumble-grumble" sound while the car was in neutral with the clutch pedal released.
Over the course of the last few weeks the "rumble-grumble" has come and gone.  When the car is cold it will make this noise if I engage the air conditioning system.  When the car is hot it will make this noise without the AC engaged.

The car is presently in the shop at the local dealer the gearbox removed and waiting for a decision to be made.
The dealer has confirmed that the runout on the crankshaft is well within spec (0.1mm).
The clutch plate looks fine.

I AM TRYING TO DETERMINE THE CAUSE OF THE NOISE AND IF THIS IS CAUSING ANY POTENTIAL DAMAGE.

The current theory is that the noise is due to the lightweight flywheel and that the original dual mass flywheel would absorb this chatter.
If this is the case then why did it take over a month for this noise to develop and why does it only occur after the car is warm or the AC unit engaged?

If the cause is in fact the lightweight flywheel, then will this gearbox chatter contribute to a shortened life of the gearbox, or any other part?

Is there anything I can do to minimize the magnitude of this noise?  Heavier weight oil perhaps?

My thought is that whatever was the cause of my short clutch life is causing this noise and maybe I am only HEARING the noise now because I have a lightweight flywheel.  Could the problem be caused by the two halves of the clutch not having coincident axis of rotation?


Anyone out there that has installed a lightweight flywheel, please send me a brief response and let me know if you have or have not had a similar experience and what brand of lightweight flywheel you have installed.


All comments and opinions are much appreciated.
I'm already starting to shake from withdrawal symptoms of not driving the car for a few days!!


MODS DONE TO DATE INCLUDE:
Autothority Hi-flow airbox
Dinan computer chip
Dinan big bore throttle body
Dinan stage 3 suspension
Dinan front strut brace
AC Schnitzer short shift kit
Turner lightweight flywheel
Cross-brace



Regards,
Stephen Habakus    shabakus@domain.elided <mailto:shabakus@domain.elided>
Geometric Controls, Inc.     www.geocontrols.com <http://www.geocontrols.com>
voice: 610-837-9861    fax: 610-837-9938

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