Is it making a metal on metal raddling sound to make it louder? There's a known issue with a screw above each of the mufflers banging into them. It makes a raddling sound through the whole SUV.
When the muffler is cooled off, look above your muffler or use your hand to find the screw just above your muffler. You can literally move your muffler up and down to hear it hit. You'll need to either saw it off or put a high temp rudder stopper on it that will not melt when it heats up.
That fixed mine.
good luck.