Here is
Dr Joe's recommendations on the 42mm Banebots gear boxes, which where the predecessor to the P60 model. I don't know about any for the P60.
Are you using a FP motor or on of the RS-555 motors?
Keep in mind the FP can generate significantly more torque than the RS series motors the P60 was designed for. It does work with the FP but you have to be careful how you use it because there is a risk of destroying the gearbox (which unfortunately you now have first hand experience with). I am also electrical/programing so that is the extent of my knowledge
