Abstract: A jack assembly for raising and lowering an object such as a trailer. The jack includes telescoping jack tubes which are expanded and contracted through operation of an axial screw. The screw is drivably connected to a gear drive mounted in an upper end of the jack. A crankshaft is supported within the upper end of the jack tube by a pair of end bushings and includes a hexagonal intermediate portion. A first pinion gear having a hexagonal throughbore is drivably mounted to the intermediate portion of the crankshaft. The first gear is in driving engagement with a screw gear connected to the axial screw. At least one of the end bushings is removable to facilitate disassembly of the gear drive. Rotation of the crank transmits rotation to the crankshaft and the first pinion gear in turn transmitting rotation to the screw gear and the axial screw for telescoping movement of the jack.