I posted a question earlier, but found out more info... let me begin

When you cut off your car next time, turn your radio off etc.. and listen how your car sounds when you shut it off. I went to the infiniti service dept today to see if the sound was normal, and they said it was, but I just want to doublecheck. They said the manuals' input shaft is larger and that it will make this kind of "spinning noise" when you cut the car off. It is much more easily noticed when listening from the outside when you are next to your drivers side front fender.

Forgive me for the paranoia, but I just wanted to make sure I wasnt the only one noticing this.

 

Is your AC on by any chance?

 

of course you're going to hear the gears inside the tranny spinning to a stop if you
clutch-out during shut off...

 

oh ok, it just didnt do that in my RSX or I didnt notice it. so im guessin it IS normal..

 

from 6MT.net, a guy responded saying

"all the gears in your tranny are spinning (constant mesh transmission). Just none of them is locked onto the output shaft when in N. However, I've never noticed any sound difference from inside the car, nor have I tried to listen for it. Maybe I should listen for it outside the car next time."

this helps

 

Since you only notice the sound from the outside of the car, chances are it is comming from the bell housing or engine compartment. The dealer is patially right, when you are in neutral with the clutch engaged, the input shaft is rotating. The throw out bearing which sits on the input shaft is also rotating. When the engine is shut off, the shaft stops rotating almost imediately. Inertia keeps the throw out bearing rotating on the stopped shaft for a few more revolutions and that is what you may be hearing. Another component making a spinning sound could be the cooling fan comming to a stop when the engine is turned off. In either case, it's normal.