We had a horrible time shifting with servos last year. One of the problems is that the "slider" in the trans that moves between the planetary sections pivots on 2 horizontal pins. There is quite a bit of clearance between the housing and the slider, which allows the slider to rock on the shifter pins and not mesh into high or lows squarely. You would be better off to build a custum housing and shift fork that you can space the pins 120 degrees apart. That's what we did this year. I have a few photos posted in the Gallery. This has been a very reliable system. As far as shifting method, pneumatic or a servo would work consistantly. If you are familiar with R/C car suspensions, you can use the little ball joints and Tie-rod screws to build a sweet linkage for the servo method.
