I have that, I think it's from the exhaust. I only started having that sound a few months after I installed a straight pipe. I checked and there are no leaks or discoloration near the exhaust flanges from leaks so it's not that. I sounds like it's coming from the y-pipe. I think maybe the flex joint is bad or something. I did notice that a few of the strands of mesh flex joint were torn from scraping, but the pipe it self looks intact.

 

There is a thread here in which someone came up with a decent answer. I don't recall exactly but it has something to do with the tranny fluid pressure. When the car shifts the fluid goes through a gate and that is the sound. I probably have the details completely incorrect but look for the thread. It sounded logical at the time.

 

the sound is coming from the intake systems. when the car is changing gears it briefly stops sucking air and the back pressure makes this noise. if you get an aftermarket intake system it's even more noticeable

 

i have had this sound but only when i had my non resonated test pipes, i took them off and the sound was gone, not sure if you have anymods but i would look at that first

 

I have the same sound on my X also. No idea what it is.

 

juan sounds like an exhaust leak at high rpms when the flow is greatest and when u shift the power goes down along with the flow causing some gasses to escape making a rushi air sound.

 

well i have a fujita intake and from 1st to 2nd around 5000 revs the intake really sucks air in and this can sound kinda like what you are talking about. so maybe it is just the intake. are you revin pretty high?

 

I have the same sound. My car is in the shop for it's first round of scheduled maintenance and I reported the sound. I've also noticed that when I shut the driver's side door (and it's really quiet around me), I hear something rattle underneath the car, like a loose heatsheild or something. So, I was thinking that maybe the noise was just that...a loose heat shield. Infiniti is checking it out. I should have my car back today, so maybe I'll have a definitive answer then.

 

I have the 07 sedan S with 4500 miles now.. no sounds yet.. I hope it stays that way! If you figure it out let me/us know so I can watch out for it.

 

Its not a bad thing. I havent noticed any issues in drivetrain because of it. Im use to it now so if it ever went away id be worried lol

 

it's just the intake

 

I heard it today while accelerating moderately hard from a stop. Pffffft, right at the shifts into 2nd and 3rd. I had the window down and it was fairly loud. Impossible to localize the sound. I wasn't accelerating that hard and it seemed like the car was doing something to soften the shifts. I'd be interested if it does the same thing under hard acceleration.

I've got about 1300 mis on G35x and it's the first time I've heard it. Not really worried, but I'd like to know if this some kind of a problem that needs to be addressed or just normal behavior.

 

I've gotta say that I throw my support to the intake issue. I have an '07 6MT coupe and never heard that sound until today....the very same day I installed a Fujita Short Ram CAI. I checked all my clamps and they are all solid. It only happens in a certain RPM range under hard acceleration. If I baby the pedal, it's quiet as a church mouse.

 

church mouse ehh???? never heard one of those

 

I've noticed the same sound since I bought it four months ago. Not sure what it is but I like it.