When I shift the transmission into drive or reverse the transmission buzzes for about half a second then makes a grinding sound. Sometimes when it does this the car hops a little bit. And when I was four-wheeling the other day I backed up in 4Hi and cocked the wheel all the way over and was bringing it back it made a loud metallic popping sound. I brought it to the dealership under the 30 day warranty (just bought it) and they said it was in normal operation. Any ideas?