Nissan told me to go suck an egg when I asked for transmission replacement under warranty a few years back. Over 100K miles now and no change. It seems in my experience the scratch is most noticeable with a quicker shift (4-5) on a cold transmission at lower RPMs. I've also found that a slower shift or double clutch with proper rev match pretty much eliminates any noise regardless of the temps or speed.
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2011 370Z 6MT Sport Gun Metallic | ARC | CJM | Ecutek | FI | Fujimura | R2C | SPL | Stillen | TWM | Z1 | ZSpeed | |