[Alex.q]

Andymark has the CAD assemblies and pictures online if you want to take a look at them. Basically, the gearbox shifts by pushing a dog gear into grooves on either a large gear or a small gear. This makes the engaged gear the one that transmits the torque and the other spins freely. You only need one piston for each the gearbox. Unless you make a custom shifter, i don't know of any other place teams have gotten shifters other than the Dewalts (I don't knowhow these compare with respect to cost or functionality).