Here is the type of gearbox i suspect he's using
i used to sell the tanks, the fact that you can get replacement gearboxes didn't fill me with much glee, now we only sell Tamiya 1/16 th tanks, 8 times the price but not as fragile but for the price the cheap toy tanks are hackworthy, also the gearbox alone would be usefull for differential drive, maybe a balancing robot