[lincpimp]

Not sure if you can use the velineon system, but if you keep the overall speed low you can most likely get away with it. Gearing would be 14t clutch bell and a 40t spur. This would give you about 35mph on 11.1v lipo, which would be about as much as the vxl motor can handle. A bigger clutch bell (higher top speed) will most likely cause the system to overheat. I would keep a very close eye on your motor and esc temps during the first few runs, just to be safe! You do not want to cook the motor and esc! Your lipo choice is a good one, stick with that and get away from the nimh, their excessive weight and poor power production will only cause issues. Plus you would need about 20 good 4000 nimh cells to equall the 8000 lipo, and they will weight at least 2.5 times as much.