A drilling assembly that includes a drill string, a drill bit assembly, and a transmission sub disposed between the drill bit assembly and the drill string. The transmission sub includes a first tube attached to the drill string and a second tube rotationally coupled to a downhole end of the first tube. The second tube is coupled to the drill bit assembly. The transmission sub also includes a clutch assembly coupled to the first tube and has mechanical engagement features configured to simultaneously engage mechanical engagement features of the first tube and mechanical engagement features of the second tube to rotationally lock the first tube to the second tube. At least a portion of the clutch assembly moves along a longitudinal axis of the first tube to disengage the second mechanical engagement features of the second tube to rotationally unlock the first tube from the second tube.