I know the noise you are talking about, its more like a chattering noise. When I first heard the noise it freaked me out
because I thought the transmission was jacked up, then I searched the forums and found out its normal for 370z's.
As you get smoother with the shifting it will not happen as much, I can't remember the last time I heard it.
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2014 370z with Sport Package Brilliant Sliver
2006 Brilliant Silver G35 6MT Coupe Sport / The infamous Oil Consumption defect ended our love affair