Interesting, that the fancy track powered Bachmann engines/locos had so many issues. I'm still running my first Bachmann Big Hauler 4-6-0 on 3S LiPo 2000 mAh rechargeable batteries and modified electronics for DCC-like control. Never a problem with gearing or wearing out the motor brushes: it just keeps working!
I did replace the sound stuff with a homebrew board, and added two more wire contacts to the drum on one driver axle to get the proper four chugs per revolution. I'm thinking about going to Blunami to have the rest of the sounds: whistle, bell, etc.