Wade will prolly chime in on how to change a 2spd to a center diff...if I remember right he sells a complete setup that drops right in...

but anyways in my opinion 2 spd on an offroad rc is useless...just another thing to mess with (trying to get it set up right)...but I guess its on how you use the rc...if you run it up and down a street and do very little to no offroading you might like the speed...but on track or like situations by the time u hit 2nd (if you do at all) you would most likely be close to a turn...I know a person that has a 2 truggies....same everything but one is 2spd the other center diff. (1 spd)..he claims if the 2spd is faster it isnt by much, also says the 3 diff is much better suited for offroading