I don't know if any of you read my posts awhile back but my flowmaster was rattling against the floor pan where it angles up to go over the axle. Well, I got a loudmouth exhaust and it fixed that rattle/bumping noise. but now i've got another problem. There is a rattling coming from the back, almost sounds like its in the hatch. but theres nothing in there besides the spare and the jack. And sometimes at idle id sounds like the rattling is coming from the trans. Its not the tranny mount, its not the catback. Is there anything else i should be looking for?? I'm puttin the car up tomorrow to see if any of the suspensin it maybe broken but the car seems to ride just like it used to. Sorry for the long post. Any ideas?

 

putting the car up on a lift is the best idea for now, that way you will be able to see and hear where its coming from, if any part of the exhaust is hitting the frame it will vibrate, remember to LM's are loud i have one, and if something is loose on the car it will rattle

 

Loud Mouths can cause all sorts of rattles inside the car as well as outside, like chasmanz28 said a lift, or a set of ramps is the easiest way to start looking for it.