gear and axle
 

i've encountered a problem here and really need help.
my BCG doesnt run well, cause of the the gear and the axle doesnt rotate together, so the gear tends to rotate freely whileas the rear wheels doesnt turn. Anyone has a solution??

Your motor is more than likely not mounted properly. Take out the motor and put it back in, insuring that the clip goes all the way in and has no play. Hope this helps.

you might want to check that the gear thing is the right way round. the larger section goes against the chassis.

hope i helped

If the gear on the axle turns on its own, then you'll have to dab a little bit of super glue or some other liquid adhesive to the axle right where the gear is. I remember someone mentioning this somewhere in another thread. If you add too much then the car will slow down due to increased friction between the chassis and the axle.