Just re-read your post. On the humming, have you broke-in the gear sets? I had a damaged set that I was unaware of and was test running my Panther G straight out of the box before disassembly to make sure it at least work before tear down and voiding the warrenty. Well I had receiver hum and the tank ran erratically and then stopped and smoke billowed out. Yep, fried the main board. On examination, one the the gear boxes had a bent axel and canted gear. Enough resistanenc to fry the board, so be caefull and take a look inside to see if all looks normale.

Jim