A height adjustment device for a transit shaft and arm assembly that enables height adjustments without significant disassembly of a transit door. An additional advantage is that the device does not require the use of shims, spacers or adjustment rings to adjust the height of the shaft and arm assemblies. Rotation of a nut threaded on the shaft allows for the adjustment of how much of the shaft hangs below a support member and a bearing. A surface of the nut bears on the bearing and the attached shaft and arm assembly hangs from the bearing and the support member the bearing is attached to. This arrangement allows the arm assembly to pivot along the longitudinal axis of the shaft. This arrangement also allows the height of the shaft and arm assembly to change with changes in position of the nut by threading the nut along the shaft.