A lift gate apparatus for a truck or trailer body is provided that includes a platform and a drive mechanism operable to pivot the platform between a stowed position and a deployed position, and vertically move the platform from a bed-level position and a lower than bed-level position. In some embodiments, the drive mechanism utilizes a pneumatic motor to power one or both of a pivot drive and a lift drive. In some embodiments, the drive mechanism utilizes one or more pneumatic cylinders within the pivot drive or lift drive. In some embodiments, one or more pneumatic cylinders are arranged to both pivot the platform and vertically lift the platform, thereby combining the functionality of the pivot drive and the lift drive. The emergency brake system of the truck or trailer body can be used as a source of compressed air to power the pneumatic motor and/or cylinders.