Recently my 2004 g35 coupe 6MT gears have been grinding when shifting somewhat fast at high rpm. I don’t drive very hard but when I do give it a little push at higher rpm then shift my gears grind pretty much through 2nd 3rd 4th gear I’d say. I’m not a big car guy so I can’t really diagnose the problem on my own, sometimes before I shift I can predict (even feel) when the gears will grind so I take a second or two before shifting to let whatever the f- in the transmission grab, synchronize or whatever. I eventually will change all my fluids soon so I plan on seeing how much metal has been shaved in my transmission lol. It’d be cool to get some info or ideas of what could be the problem, maybe it’s some serious crap or maybe I just suck driving manual who knows.

 

Hopefully you just have worn fluid there. Not too uncommon for the synchros to go out on the older CD trans. Late 04 G coupes and 05+ have the CD009. These typically don’t have issues.