Lately, my transmission (ahem...trans-axle), has been rattling at higher revs in 2nd and 3rd gear. If you've ever taken a stick and dragged it across the face of a chain link fence, that's what it sounds like. Has that distinct ping to it. I can't tell if it's bad gas (don't laugh), something's loose, and issue with the trans-axle, or something major is about to happen. I'm planning on getting it checked out when I take it to get it's oil changed and maintenance done sometime next month. Any ideas as to what may be causing this strange noise?