The present invention is a highly stable gear drive adapter featuring a stabilized drive assembly. The drive assembly includes a drive shaft connected to a gear holder assembly, which couples to a gear shaft assembly, which in turn couples to a tool adapter. Each component of the drive assembly stabilizes or is stabilized by another component. A cover aperture and a drive shaft bearing stabilize the drive shaft laterally. Additionally, an interface between a polygonal band on the surface of the drive shaft and a polygonal aperture in the gear holder assembly also stabilizes the drive shaft laterally. A retaining ring and a shaft stop stabilize the drive shaft axially. The gear shaft assembly includes two gear shaft bearings laterally stabilizing a gear shaft and a gear shaft channel that contains the drive shaft bearing. A tool adapter bearing stabilizes the tool adapter.
