wonder if I can swap out the motor for a bigger one? 
That would be my inclination also
but then I read something kind of interesting.
Usually bigger is better but I read on an RC forum that for certain sizes, bigger is not always better. I think that they were talking .12, .15, and .18 engines. They said that the .12 in comparable cars is faster than the .15 and .18 engines due to the design. .12 engines have had more racing tech put into it compared to the other engines and also they said something about the shorter stroke allowing it to rev faster and higher. In that discussion they also mentioned other engines too, I forget the sizes but maybe comparing a .25 to a .35 in a monster truck of somesort and they said the bigger engine couldn't go that fast. Might have more torque though. Again, just what I heard on that forum.
I have always wondered if a weed wacker engine could work in a 1/8 scale 4WD frame.... I have one of those lying around here.
Don't know what to do about a tranny though.
