Gearing wouldn't make any odds, it the motor rpms that do something like that; first shattered Castle rotor I've seen from these motors...
Contact the support department:
http://www.castlecreations.com/support.html
Is the inside of the motor damaged, damaged windings of stator? If not, a rebuild kit should do the trick, otherwise whole new motor needed- if it's over 12 months old then it'll be a non-warranty repair fee...