I don't know whether GM sell them separately or not, so I suggest you email David (wyh@goldenmotor.com) and ask him direct.
If you tell him exactly which mini motor you have, he should be able to tell you if the planet gears are available separately.
It might help to also send a photo of your motor/gears etc., as there have been different versions of the minimotor.
Please let us know the outcome, as this may be useful to others who may require replacement gears.
Alan
