Actually it's the input shaft spinning the gears in neutral position. There is no spec for bearing end play on our 6MT. We actually had a long discussion about this down at Nissan MT Class. You're hearing the gear mesh, even though they're helical cut they still don't mesh tight enough to be quiet. Using a higher quality gear lube can help reduce the noise. However, the fact we keep no tolerance on end play it allows for a much louder gear box. You want to hear a really loud trans, look at the 03 350z first 4 weeks of production. Most were warrantied and replaced.

That makes a lot of sense, but why does the noise go away with the clutch pedal in if it's the input shaft? And I was under the impression the dual mass flywheel was responsible for some of the noise.

With the clutch disengaged the input shaft is not spinning with the engine rotation. The input slides into the pilot bearing but it's the disc it self that rotates the input shaft, sometimes called the main shaft. Depends on which literature you're reading. We use the dual mass flywheel to absorb some of the resonant vibration from the gear box itself. You tube some 370's that have replaced the dual mass with a race setup. The noise is horrible, I've swapped stock units back in to customer cars because they become so annoyed with the amount of noise the trans makes without the DMF.

Don't need to youtube it. I just have to listen to mine. :rofl2:

what would you guys recommend for a little more performance but no annoying noises flywheel wise? stock weight is something like 33lbs, no? is there anything dual mass but around 22? Or do all light weight flywheels take out the dual mass part?

All of the aftermarket ones I found omitted the dual mass. I went with a lightened steel flywheel, and the noise is fairly obtrusive. I can't imagine how bad an aluminum flywheel would be. It's worth it to me, though. I love how fast the car revs now. Launching it is a little trickier between the light flywheel and a grabby clutch.

If you remove the dual mass you will nearly double the resonating sound of the gear box. So no there is no real option that I've seen yet. Not to say there isn't an option. If you can find a DMF Aluminum fly wheel you might be able to regain some of the dampening properties. Highly unlikely though. However, for those going for the performance they accept that it comes with draw backs. Lower MPG, more difficult city driving, noises, ect, ect. It's what that little knob on the dash is for. Turn the tunes up and enjoy the ride. ;)

I didn't notice a mpg drop, but the flywheel was installed at the same time as the turbos. That definitely cost me some fuel economy.

im really glad i said something. wrong, but still. learned a lot about where the noise was coming from that otherwise would never had been mentioned lol.

It's normal, even my R35 has that clinking sound.