Back Driving a Versa planetary gearbox

[asid61]

Download the JVN calculator, go to the "Rotary mechanism" tab and input your stuff there if you haven't already.
A minicim has a stall torque of 12.4 in*lbs, so on a 100:1 reduction that's about 1240 in*lbs (minus efficiency losses). I personally don't like running motors with current for extended periods of time except on the drivetrain, and even then not really. I would try to get maybe a quarter of that stall torque max, but I have no basis other than experience for that recommendation. If you wanted to figure out exactly how long you can put a current on a motor, Vex has graphs for motor power and heating.