So far every loaner of various years and make of a G I have driven had this rattle... its annoying but I figured it was a normal design flaw

 

Hmm, now that you mention that, I have to say that the loaner I just drove for a week while my 6MT was in the shop had a rattle to it. Of course being a loaner, I just assumed someone had filled it with cheap gas, but besides that, it was an automatic. Is that the issue then? Is it only automatics? Does anyone have a 6MT with this rattle?

 

Anyway of hearing a sound or a video recording of a engine knock? I don't think I have ever heard one

 

I'll try and record it on my iPhone and see if it is audible.

 

For what it's worth, my 08x sounds like it has an exhaust leak too when making hard shifts between gears (automatic trans). It literally sounds like there is a slight exhaust leak getting out somewhere during the shift. Then I read this thread and figured out that it's just an Infiniti design flaw....something that I'm sure can be remedied with aftermarket exhaust

Just realized I posted that I have an 08x with an auto trans .....DUH....

 

What do u mean hard shifts? U mean driving in manumatic mode?

 

6MT with no rattling or knocking sounds throughout the rpm up to redline... i do have aftermarket FI exhaust which could be a factor considering most complaining about teh sound seem to have the stock exhaust and believe the sound is coming form the exhaust.

 

let me guess, only happens when its cold? it may very well be the mufflers. 07+ even G37's mufflers all have a design flaw in them. The baffles inside of them come loose thus causing that noise. Give it a test, take them out and drive around. I guarantee the noise will go away.

 

Nope, I don't drive in that (IMO) stupid mode. I drive my car in fully automatic mode, or "DRIVE", all the time. And when accelerating hard, almost exactly at the shift point, you can hear what sounds like an exhaust leak under the car. It's rather NON sophisticated sounding......car has 40K on it now.

I'm assuming a catback exhaust would remedy this problem, that is, assuming that the problem is the mufflers and not the factory Catalytic converters...