Rattle in back of civic hatch
 

I have a 95 civic cx hatchhback that has a full 3in exhaust to a 4in tip. when i first had it installed it sounded good, kinda loud but sounded exactly as it should. that was about 5 months ago but in that last few weeks, there is a really loud rattle in the back. i noticed that the exhaust rests against the mount for the lower control arm, so i wrapped it with some header wrap to add some cushion but it makes no difference. it almost seems as though the back glass is vibrating as if its not latching securely. however i am not sure. i do want to downsize the exhaust, i just need to figure out what is going on back there. if anyone has any suggestions on what to look at or how to fix it, that would be greatly appreciated.

The only way I've ever been able to address rattles is systematically. Basically just start securing things and testing, or have a passenger monkey about in the back and press on various things while moving to try and re-create and narrow down the issue.

Time consuming and a pain in the butt, IMO, but has always worked in the long run for me.

Check/fix/replace hangers and/or vibration isolators.