I just got my black on black rx8 2weeks ago. I noticed that when its at neutral, there is a humming/whirring noise which goes away when I depress the clutch. Is this normal? or should i have it looked at? I've never had this happen in other cars, so I dont know if its normal in rotaries or whatever.

 

normal.

 

so then its not normal
have mazda check it out

 

Normal may not be the word for it.

Every RX-8 that I have driven or been exposed to makes thes same "whirring" or "grinding" noise when in neutral.
Disengaging (pushing in) the clutch stops it.
It is likely that it is the gear set rotating, though some have postulated that it is the release bearing.
If it were the release bearing, the noise wouldn't stop when you press the clutch.
To some extent, my Miata makes the same noise.
Whether it is normal or not remains to be seen.

 

look, it's an Aisin 'box based on the design for the Miata. in Miata's, there is the same whirr from the spin of the output shaft.

don't let Rikki freak you out with his horror story as he's the only one to break his transmission yet, and that's AFTER he repeatedly beat the living christ out of it (burn outs, power shifting all the way down the quarter mile, etc). i don't know why he said that, but whatev...

in any case, this has been discussed at length in many other threads. use the Search button at the top to find them, give 'em a quick read through, then add onto the end ('ressurect' if necessary) if you have anything else to add.