Mine has 2 noises,
1st I have not found yet, it sounds like a little steel ball dropping on a spring, left side, only when tire is on the ground
& you push roll it. NO NOISE once you jack in up & spin the tire.
2nd check to see if your muffler is touching/rubbing/binding on the "Heat Shield" that is attached to the rear floor.
Mine was after some trail abuse and was actually having the muffler catching the end of the heat shield at the
"Crimp Roll" on the back muffler end.
I thought it sounded like I broke a spring, with a "Snapping/Popping" sound.
Hope it's something this simple....I was once I found it.
CAPT