Originally Posted by lll2for3lll
Sounds like something with the exhaust if it goes away when hot and returns when cold.
^This. I had nearly identical symptoms (a metallic noise when cold right around the 3000rpm range, not duplicated in park or netural). Went up and down the exhaust with a rubber mallet looking for a loose heat shield or something and was never able to find it.
Had the noise for 4+ years.
Did some work on the transmission which required dropping the exhaust, and when everything went back together...no more rattle. Have no clue what it was, but it's gone now.