hello.

I have Civic 97 LX
when people sit on the back
especially going reserve
I hear rattling sound from muffler
I'm not sure is sprint or suspension
but only happen when there is load

 

probably have a little contact where the exhuast system does up over the rear suspension..

 

Do you have a rear swaybar? If you do, the pipe is probably hitting the swaybar.

If you don't have a rear swaybar, like mentioned, the pipe might be hitting the lower control arm. You could try messing with the hangers on the muffler but chances are you wont get much out of it and might have to deal with it.

 

The suspension and sprint needs to be replace on rear they wearing out the guy at shop showed me...

 

check your exhaust heat shields...they tend to loosen up and make a rattle sound