Abstract: A limit switch assembly for a screw jack includes a worm screw jack assembly, a gear mechanism and a limit switch mechanism. The worm screw jack assembly includes a worm shaft, a worm gear and a screw jack shaft. The gear mechanism includes a piston, an adapter block, a planetary gearbox, and a gearbox shaft. The piston is drivable by the worm gear and engages the gearbox and the gearbox shaft extends out of the adapter block on an opposing side of the piston. The limit switch mechanism is coupled to the screw jack by the gear mechanism, and includes at least two limit switches operable to control movement of the screw jack shaft. The planetary gearbox may have interchangeable ratios to accommodate worm gear screw jacks with an increased number of gear ratios, drive screw lead, and length of travel requirement combinations.