[Yetti]

one of the other things to look at is the exhaust. if its touching the chassie it will do the same thing. if by chance you can block the drive wheels and have someone look under it while its in reverse you may have a better veiw of the noise or at least a closer area to look at when its off and you can get completely under it. DO NOT get under it with any body parts you can't afford to loose while its running. leave that for trained mechanics...(Thier expendable!)

use a pry bar to lever againest the exhaust pipe mounts and trans mount to see if they are torn. it doesn't take much effort if its torn so don't force anything if it doesn't move.