Electro-
I've had my NSX for a few weeks now and was experiencing the same problem that you were; it would only grind when going from 2nd to 3rd when speed shifting. I corrected the problem with this theory: I came from a 99 Civic SI 5 speed. The gears on it are not even close to how tight or close they are on the NSX. When shifting from 2nd to 3rd on the Civic I had to literally go up halfway and then over. So when I got the NSX, shifting from 2nd to 3rd I would tend to go up and over. It usually got stuck in the middle as I let the clutch up and it would grind, but I would still get it into 3rd. Last week I was experimenting with shifting and noticed that if I just went straight up, it would glide right into 3rd without the grinding. I think that's because the gears are so close, you're not going STRIAGHT up, but just about. Another thing that I noticed when shifting was to let the tight, short throw do the work and not my arm. When I grabbed the shifter just below the knob with my hand wrapped around and not on top, letting my forearm rest on the console, I would use my wrist action more. It was a lot easier to shift, and I stopped "forcing" the gears in and let the car do the work. When slamming on the gas and going through the gears aggressively, remember to be aggressive with the gas and clutch, but not the shifter. You want to shift fast, but you don't need to shift fast AND hard. That's when you'll run into problems. Go straight up and down with "finesse" and the gears will fall into their proper places. Once again, when going from 2nd to 3rd, try to hold the shifter on the pole and not the knob and shift with the wrist. It's kind of hard not to be aggressive with the shifter because of the adrenaline and all. Plus your being aggressive with everything else, i.e. gas, clutch, brake, steering. Just think of it like when you take your left hand and make continuous circles on your stomach and take your right hand and tap on the top of your head. If you can do both of these simultaneously, then you can do this. Hope this can help from my experience with the same problem.