fix the faulty ball diff's spur gear
 

I decided to rebuild the ball diff recently and found that the metal plates of the ball diff were pressing against the plastic spur gear instead of the metal balls. The reason for this is that the spur gear was thicker than the balls.
After sanding down the spur gear of the ball diffs, the performance of the ball diff was much better.

Question: Does the version2 have this problem? If it's not a problem with the version 2, I'll probably buy the whole rolling chassis when something breaks.

didnt have the problem with the version 2

Thanks 3ST. That explains why you love the Mini-X so much while I initially hated it.
I'm gonna get the rolling chassis and rediscover the experience. :)