Holcomb,

Your starter has a over-running clutch enclosed in the starter drive. Some call it a roller clutch. It is suppose to lock up in one direction and allow the starter motor to spin the engine. As the engine starts and over speeds the drive, the over-running clutch allows rotation as the starter drive is thrown back into the starter. I will guess that when this fails it goes buzzzzz!

I wonder why this wasn't checked when the starter was rebuilt...maybe it offers enough resistance by hand, but not when blasted by the starter motor.

Stuart