As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IMMEDIATELY AFTER GEAR RETRACTION THERE WAS A CONTINUOUS VIBRATION / SHUDDER AND LOUD NOISE IN THE NOSE AREA. NOISE AND SHUDDER STOPPED AT 500 FEET WHEN PACK WAS TURNED OFF FOR LANDING. RE-SECURED LOOSE ACM DUCT RT EXPANSION SIDE PER DACO M/M 21-55-1. ALSO RE-SECURED LT PACK CURTAIN SNAPS THAT WERE OFF. PACKS CHECKED SERVICEABLE PER DACO M/M 21-55-00.