its similar to almost all drag cars, most teams run a transmission based off the gm powerglide, which is a 2 speed automatic, but the have a manual valvebody to control what gear they are in, other manual valve body trans used in monster trucks are: th350, th400. C6, tourqueflite, but these are very uncommon, then there are trucks like the hall brothers that run a Lenco 2sp trans, not sure if they are running a centrifugal clutch or torque converter, and then xdp the diesel runs a single speed reverser box which all he has is forward, neutral or reverse nothing else.