Just bought my '08 g37 coupe (74k miles) about a month ago and everything was good until I heard a rattle sound coming from my exhaust. It rattles when I'm in park and when I go into 2nd gear at low speeds. I can also hear a rattle when I close my driver side door. I've been researching for a while and I wanted to diagnose the problem before I took it to the dealer. I'm still covered under my dealer's warranty so maybe it's just a heat shield and not something else.

 

you can get a long screwdriver and lay on the ground to poke and prod the exhaust heat shields to see if any are loose. may have to jack the car up a little - i only got my G37 yesterday, so i'm not familiar with how much room you have to move under there ...

i had a loose one on my Evo, and it made a horrible sound - i was scared the engine or transmission was going to grenade.

if you find a loose one, and aren't worried about appearance (that nobody with see anyway), put as many large hose clamps around it, tighten until snug, and problem solved.

edit: just saw you are under warranty, so let the dealer fix that ****