The Fisher Price motors will mount on planetary transmissions available from
Banebots.com in various output speeds. We have also used the plastic gears mounted between plates to create a transmission, and have abandoned the plastic housings. To speed it up, we have eliminated one or two spur gear stages. They will hold up well if you don't put them into an application that will stall the motors. You will need a milling machine to bore the plates to mount the gear shafts the proper distances apart.