A surgical instrument includes a body, a shaft assembly, an end effector, a stapling assembly, and a drive system. The shaft assembly extends distally from the body. The end effector is disposed on a distal end of the shaft assembly and includes a first jaw and a second jaw. The stapling assembly is supported by one of the first jaw or the second jaw of the end effector. The drive system includes a shift mechanism configured to selectively modify a mechanical advantage of a drive input driven by a motor and used to power one or more functions associated with operation of the end effector.