to expand on what Matt C said here are two good sources for transmissions for the fisher price motors.....
http://www.banebots.com
http://www.andymark.biz
We have used the banebots transmissions with much success since 2006. In fact a banebots transmission with fisher price motor is how we ran our 2006 conveyor system. Just a word of caution, the banebots will destroy themselves under a cantilevered load.
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