The twin force tranny is doing great. I haven't broken a thing in it all this time. I chose the twin force tranny because it is the toughest and simplest design of any tranny I have found. Also it is more suited to an electric conversion since it is for an electric truck. Therefore, there is no mechanical braking or one way to deal with like on nitro trannys. I don't like a center diff because it takes a lot of the fun out of running a monster truck because it virtually eliminates wheelies. I don't even like them on buggies. My hyper 7's is so tight with thick fluid, it barely gives. Center diffs are for racers so the chassis will stay planted and corner better. I am just a basher, so I either don't use them, or I lock them up.