thanks for the post... i have been driving it like this and i noticed a few things different
1. only the opposite wheel spins (in the opposite direction) instead of all 4 in the same direction.
2. less turning radius than the ball bearing red one
3. more torque.... drifting without drift kit.....!!!!!
4. more speed (i think less power is lost due to the slip in the ball bearing differential
i would reccomend this to anyone even if they dont have a broken ball differential (dont open it up... LOL

put the 2 cups in opposite ends and spin them if they spin in the same direction its the ball if they spin in opposite directions it is the gear diff.