Rocks in the skid plates
My 2012 JGC Overland Summit gets driven about 15 miles every day over a fairly rough, steep, gravel/dirt road. In 4 months, it's gotten two rocks on top of the skid plates.
The first rock was maybe 4" x 2" x 1" and caused quite a bit of consternation - it made nasty clunking noises and then got jammed between the transmission and the skid plate which caused the whole car to vibrate. We didn't realize it was a rock, took it to the dealer, and the mechanic finally found the rock on the second visit (he at first thought it was a "major transmission problem").
The second rock was slightly smaller and I was able to fish it out by cranking the Quadralift suspension up high and groveling underneath.
I wrote this for two reasons:
(1) If you hear clunks or get nasty vibrations, it might just be a rock on the skid plates.
(2) Has anyone else had this happen? I suspect that I might be pulling rocks out regularly. I've never had this happen on other vehicles.