Gearbox Gurus, how loud can it get? (G50/20)
 

Hi Everyone,
Well the Tilton carbon/carbon clutch is completely sorted and the car runs great under its own power. I also took this opportunity to go with an 8 lb Porsche motorsports flywheel as well as putting in new transmission oil (Red Line 75W90 GL5 spec).

However, I do have one concern that I would like opinions on before I keep driving the car.

Here are the symptoms:
After the car warms up there is a kind of deep tone rattling noise (not really fast) that sounds as if it is coming from the transmission. This noise is present whenever the clutch is engaged (pedal out, in neutral as well). However when the clutch is pushed in it goes away immediately. Also when in neutral the noise will go away when you move the shifter toward a gate and put pressure as if you were thinking about putting it into gear. Also keep in mind that there is no sound padding/deadening material in my interior whatsoever (so I can hear anything that goes on pretty well).
The car still runs great, clutch hold is amazing and easy to get into/out of gear.


Tilton's diagnosis after speaking with some other Porsche tuners:
They said that it is most likely the gears moving around causing the noise since the dual mass flywheel has been changed out to an 8 lb unit and no longer has the dampening capabilities to keep the noise down. The clutch pack is also Alot lighter at only 5 lbs. All in all they are saying that the G50 is normally a kind of loud gearbox and that this is not abnormal.

So, I would like opinions on if this sounds reasonable (seems to be so given the symptoms). I've just never had experience with the gearbox noise of a G50/20. Would the drastic change in flywheel weight make this difference? Anything else I should check?

Also would the Red Line oil make a difference? Perhaps a different oil would help quiet it down slightly.

If this is normal then I can go on and enjoy the newfound performance as noises don't bother me in the least unless they are linked to something problematic.

Thanks in advance for any insight.

Princeton, I was recently talking to Steve Weiner of Rennsport and he told be that that sound was the gears and quite normal in my G50/50. Changing to a lighter flywheel or clutchpack without the dual mass will cause more noise. I will be enduring a bit more noise myself as I am replacing my rubber-centered clutch disc with a spring-centered one.

Cool. Thanks very much. The thing is I have this flywheel that is 1/4 the original weight and less than half of even the RS flywheel weight. Also the clutchpack has no springs at all, just titanium and carbon/carbon plates. Hopefully this is the cause of the noises.

I guess I have a little less to worry about then. :)

I find my G50 to be very noisy. I also find that it is the noisyest at 2k rpms with a light load. I have an early 930 clutch setup on mine.

Yep, the G50 in my car is very noisy, lots of sounds that sound like two metal parts spinning with some clearance between them. This is my second tranny and the other was very similar. I hear regularly that the G50 is a noisy tranny.

According to Paul Frere in Porsche 911 Story the purpose of the dual mass flywheel was to supress transaxle noise.