Durango muffler hole

If you have a hole in your muffler just replace the muffler don't patch it. The patches don't work well. It's a temporary fix. If you can't find the hole it could be because the baffles inside the muffler are rotten, have moved or fallen down. So the exhaust sounds loud even without a hole. If this is the case then you will have to replace the muffler.

how do I find out if it is the muffler can or a hole in the pipe

You physically have to look and listen to it while its running. If you live where its cold outside you will see the exhaust leak reallllly easy while its running