After putting in a different esc and motor, the granite was stuttering at throttle, and grinding badly, when on the ground. When I held it in the air and hit throttle, it seemed fine. Found the problem! That little so n so right there! That's a bearing out of the idler gear. Luckily the only other damage I found was the washers inside the diff. I'm rebuilding the diff with new bearings and guts, along with 50,000wt. diff oil.