When I start up the JK (manny tranny), I get a brief rattle coming from behind the dash in the middle. It's like the entire dash is on mounts and the engine shake makes it rattle. It also does it as I turn the Jeep off. Any ideas on what this could be? I get the rattle over some bumps too. I took the glove box out and noticed that the passenger side footwell air vent tubing was loose, but when I rattle it with my hand, it doesn't sound the same to me.
TIA for any help!