Hey guys so I have this new bad knock/rattle from under my drivers seat, near the transfer case sifter, and i'm completely clueless into what it would be. It seems to only happen when in drive at idle and accelerating at first but then goes away and doesn't happen in any other gear so i have a hard time believing it is the exhaust hitting the crossmember, also I have a feeling that it isn't the transfer case linkage because that makes it own noise already, this new one is a much deeper rumble that you can feel.
Thanks for the help!
Video of the noise for reference: https://photos.app.goo.gl/UKdWZVGQrqaS82jVA

 

Bad engine and trans mounts are a possibility. don't discount the exhaust to crossmember possibility. Very common.