Planetary gear motors or stepper motors?

I have been using a 12 RPM planetary gear motor for my robot that runs on my lawn.

What are your thoughts about using stepper motors instead because one of my planetary gear motors apparently stripped a gear.?

@Z223IA Welcome to the RobotShop Community.

To confirm, the planetary gearing added to a DC motor increases the output torque and decreases the speed. A DC motor on its own, unless it is very large and powerful (ex. a “torque” motor), spins too fast and can be stopped with almost no counter-rotational force. You will find about the same thing with a stepper motor, which is why you’ll still need to have gearing. it sounds like you just need a bigger gear motor.