I have the same situation: I pinpointed that this sound appears at 1500 RPM, regardless of idling or while driving at slow speed. I agree, it's most likely an exhaust shield issue. When car just started in the morning and RPMs were higher than idling, I went outside and found it was coming from the bottom, from the heat shield.

 

Thanks. I can confirm that at least for mine, it's not a heat shield issue. I've had heat shield issues before and this sounds more like loose chain rattling.

 

Mike, don't you have 6MT? (Sorry, senility must be setting in)

If you do, and it's drivetrain load related, and it happens at lower rpms and speed, then I'd say it's probably just the gear lash in the tranny.

 

I know, mine sounds exactly the same, like loose chain rattling. But when I lean to the button of the car I found the noise was coming from there, not from the engine, although in the cabin it sounded like the engine rattling.

 

R u guys sure it's not the honeycomb parts inside the catalytic converter going bad? I had my catalytic converter replaced at 40k, and the dealer mechanic confirmed Infiniti catalytic converters suck.... After a while they become lose and rattles under low RPMs.... Moving or parked.

 

^ It happens at a very specific speed, gear and rpm. When downshifting and keeping the same rpm or speed, it doesn't happen.

I've been trying to capture it by placing a mic in various places but i can't get it to record well enough -- wind noise drowns it out. I can fairly capture the sound from within the cabin, but not enough to really understand which noise to keep note off.

Will keep trying, hopefully a good enough recording of it will help.

 

I wonder if you could repeat it with the rear of the car on stands; just running the drivetrain in the air?


PS . . . DO NOT do this unless you fully understand how to do it safely

 

What ur using to record? a cellphone? You can do what i did and put the cellphone inside a sock. it'll block out the wind noise immensely. I had to do this because my invidia xpipe was making a noise when accelerating and when the rpms would die down. bought a magnaflow resonated x pipe and hopefully the noise will go away.

 

I typically just lift the rear with my awesome arm, core and leg strength, but there's no one to hit the gas pedal.

Seriously though, you have a good idea going on there. I wonder if a run on a dyno machine will work? That way i can have the hood open and pinpoint exactly where the noise is coming from?

I used a vid cam and voice recorder. The mic's are very sensitive, nothing short of a deadcat will work on these darned things. I'll try the cellphone+sock idea. Thanks!

p.s. What kind of noise on your xpipe? If it's a rattling at certain rpms, it could be the heatshield. That happened to me shortly after install, i bent back the shield and voila, no more rattle.

 

Nah it ain't the heat shield. The closest description i can come up with is wind passing through loose metal causing a vibration+noise. I went under the car while someone else was revving it. It's coming from almost the center on the xpipe. Even holding the rpms above 2000 you can hear it clearly.

 

I have the exact issue, except mine is usually up a slight incline at first gear at around 1500-2000 rpm. except in neutral I can never replicate it. weird

 

I have the same problem and it's only when using the throttle very lightly. The description of a rattling chain noise is the best description. I've had for as long as I can remember and it's never really caused and issue (no power loss).

Glad to see it's not isolated to my car, but to be all honest I don't think it something to be concerned with. A friend of mine is a Master Tech at Audi and said not to worry about it unless it's affecting the driveability of the car, which at this point it hasn't.

When I first heard it I know I got all paranoid, but now it's only a radio volume increase away from being just right

 

I have the same noise in my 04 g35 it is automatic though and it does it around 30mph to 40 mph at about 1500 rpm giving it gas makes the sound go away heard it might be loose exhaust manifold bolts or bolts to turbo loose? not sure yet though.

 

Sorry to bump an old thread but I would like to see if anyone has found a resolution for this yet. I have been having this same issue for a while. I think that its something in the transmission or diff since it only happens under load. I have taken a video that captures the sound perfectly but can't get it to upload to youtube for some reason.

 

I have the same issue. Just started recently. Mine is 08 g35s auto with 120k miles, original owner. In first when I accelerate I hear the noise. It will not do it in neutral, only under load. I do notice it more on inclines. Anybody get an answer?