I have a 2012 2dr rubicon with a manual transmission an 80,000. It is stock other then bumpers and roof rack. It makes a metal rattling/clanking noise when hitting bumps while in gear and on the gas, absolutely nothing when off the gas or in neutral. It seems to be worse when I have other people riding with me. It sounds like its coming from dead center underneath. I climbed under and didn't see anything obvious, nothing moves when I try to shake it. Anyone else run into this before?