The disclosure relates to a transmission unit, having (i) a housing for the fluid-tight encapsulation of at least one part of the transmission unit, (ii) a rack and pinion transmission which is arranged in the housing and has at least one gear rack, (iii) a hydraulic drive system, which is arranged in the housing, has at least one displacer unit for increasing the energy of a pressurizable working fluid of the hydraulic drive system, and has at least one chamber in which a piston, operatively connected to a gear rack of the rack and pinion transmission, can be moved using the working fluid in order to effect a linear movement of the gear rack, and (iv) a rotatable mechanical actuator, which is operatively connected to the pinion of the rack and pinion transmission and is arranged outside the housing at least in portions.