As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT, THE CREW REPORTED LOAD VIBRATION THAT SOUNDED LIKE IT WAS OUTSIDE OF THE AC. THE CREW MADE AN AIR-TURN-BACK. THE AC WAS INSPECTED BY MX WHO FOUND THE LT PACK VALVE WAS BROKEN. MX REPLACED THE LT PACK VALVE. THE AC WAS RETURNED TO SERVICE WITH NO FURTHER DEFECTS. (K)