As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT CREW EXPERIENCED AN AIRFRAME RUMBLE DURING TAKEOFF AND OPTED TO RETURN TO LANDING. MAINTENANCE CONFIRMED THE RUMBLE DURING GROUND RUN AND DETRMINED THE LEFT HAND STARTER GENERATOR CAUSING THE RUMBLE. A SERVICEABLE STARTER GENERATOR WAS INSTALLED, RUNUP GOOD AND AIRCRAFT APPROVE FOR RETURN TO SERVICE.