A gear-driven infusion assembly is provided which has a housing, a gear assembly coupled to the housing, a shuttle assembly slidably coupled to the housing and operably coupled to the gear assembly, and a tube enclosure connected to the housing. The tube enclosure is configured to house a primary drug closure such as a syringe. The gear assembly includes a spool assembly having a pinion gear and a drive spool. When the spring rotates the drive spool, the drive spool drives the pinion gear, and the gear assembly drives the shuttle assembly. When the gear assembly drives the shuttle assembly, the shuttle assembly slides longitudinally along the housing. The gear assembly may be spring driven such that a spring rotates the pinion gear about the drive spool. An overspeed protection device is also provided which has a spool assembly including a drive spool.