Q: Muffler rattling at lower RPM

What you want to do is jack it up and get under there with a rubber mallet, have somebody start listening to the rattle, and hit them up with the mallet. After this, the mufflers will often no longer rattle. A lot of times, it is the catalytic converter that rattles. The catalytic converter is before the muffler.

Now, if it runs perfectly fine and no Check Engine Light is on, you can just ignore it. Because, the only way to fix it is by replacing it. So, if it is the catalytic converter, it costs an awful lot of money. But, if it is just rattling and running okay, you can live with it. The same thing goes for the muffler. If it is the muffler that’s rattling, the only way to fix it is by replacing it. So, if it runs okay, you can live with it. But, if you don’t like the noise, figure out which one is making it and then replace it.