So can it be a matter of just maybe tightening it or welding it? It makes that shaking noise when I take off and also let's say I was suppose to be in 2nd gear and I put it in 3rd it makes that noise. Some guy said, ( I could be way off ) but he said something leaking in or out from the exhaust and that's what's causing the noise. Or what else can it be?? How can I fix it? It's a 96 ex civic

 

Check for leaks by blocking the tailpipe with the engine running. Leaks will make a hissing noise. Note that stock mufflers have small intentional drain holes near the bottom that are normal.

To find the rattle, get underneath the car and shake stuff around to see which part it is. The heat shield on the catalytic converter is a common problem. You can put big hose clamps around the whole thing to re-secure it, or just remove the shields.

 

So if I get a new exhaust I don't have to worry about trying to find where it leaks out or where it's loose? When you get a new exhaust all the piping is re-due right? Or do I still have to find where I need to patch it up? It is a stock exhaust.

 

If you're sure what you are hearing is from part of the exhaust, replacing the whole system would cure it. It is not common to replace the entire system starting from the engine though. Usually the back half of the system (the pipes after the catalytic converter) rusts out much faster and that is all that needs to be replaced.