A height adjustable support for semi-trailers includes a shaft tube body modable on a chassis of a semi-trailer, a slidable support inner tube arranged in the shaft tube and having a foot mounted to an end region thereof by a nut located on a spindle which is drivable by a transmission, wherein the transmission has a switchable spur gear region and beveled gear assemblies. The switching region of the transmission is formed from a lower-gear pinion and a fast-gear pinion each adapted to engage a crank drive, and a low-gear gearwheel and a fast-gear pinion each adapted to engage clutch coupling elements, wherein power is transmitted from the crank drive via the low-gear pinion to the low-gear gearwheel and alternatively from the crank drive via the fast-gear gearwheel to the fast-gear pinion. An output shaft and a tab drive unit are supported in a rotatable manner, wherein the tab drive unit comprises the fast-gear pinion and a fast-gear beveled pinion that are connected to one another in an unrotatable manner by a connecting member.