i couldn't have said it better.

 

Hopefully down the road in a few weeks I'll be able to have some time to investigate it. If I find what it is I'll post it. But hopefully if someone finds it before me, they'll post it too.

 

i'm goinna take it to the dealer monday

 

One rattle I noticed was passenger seatbelt flopping around.

 

You might look to see if something underneath the hood on the firewall is not obviously loose. Maybe something they forgot to tighten.

It is possible it could be underneath the dash. I always get neck ache looking underneath the dash upside down in the seat.

 

I've been in Rattle hell also with my Dash for 6 months.
Went to the dealer 3 times with it. This last week they had it for 3 days and said that the Speaker grill mount or something was flexing. They ordered a part and replaced it.
Drove it home and it was great!
Drove it to lunch and I heard it but seemed like it was 80% fixed.
Today I went out and it was a bad as ever . SO PISSED!!
You hear it most when turning left or right up a drive way. The weirdest nasty creaking sound.
Gonna give them hell on Monday!

 

So I just drove it around with the temperature thing in mind.
Blasted the A/C for 5 min and it still made the sound.
Then Drove it around for 10 mins with the Heater on and it did seem a bit better, but it is cool at night still so that might defeat the purpose

Then I started playing with that Cowl thingy and it definitely is a huge cause.
I put little tie wraps in between the rubber and windshield and it still pops and creaks when you shake it.
I was hoping it was maybe the rubber rubbing on the glass.
It doesn't do it at all on the passengers side.
I think the Dealer fixed part of my problem with the speaker Grill but I really think it was a 2 part rattle and half is still in full effect........8(
I wish I could figure out how to take this thing over to see if it's that.

 

I had this same problem. Litlle tinny sounding rattle under the dash, sounded like it was coming from the drivers AC vent. Pulled off the under dash cover and found there is a little sheet metal L shaped bracket with a eletronic module mounted on it. This bracket is only mounted from the front dash frame with 2 screws, and extends back maybe 5 inches. Tapped it a few times and got the same sound, just took a couple of tie-wraps looped it through a hole and tensioned it forward...to the steering colum I think...that was 3 months ago and haven't heard it since a really chessy setup.

 

OP Actually there were some loose screws... it was in the drivers seat. He has since moved on and now resides at the Gen5 Camaro forum. Thank GOD for that.