As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURN BACK TO DEPARTURE DUE TO A LOUD VIBRATION FELT ON CLIMB OUT. THE AIRCRAFT LANDED OVERWEIGHT. ALTHOUGH NO EMERGENCY WAS DECLARED THE AIRCRAFT WAS MET BY AIRPORT EMERGENCY CREW. MAINTENANCE COULD NOT IDENTIFY THE SOURCE OF THE VIBRATION BUT ADJUSTED R/H ELECTRONIC BAY VENT VALVE AND TIGHTENED CLAMP ON R/H RAM AIR VALVE DUCT FOR PRECAUTIONARY PURPOSES.