As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AFTER TAKEOFF UPON GEAR RETRACTION LOUD THUMPING NOISES. NOISE CONTINUED MULTIPLE TIMES IN EXCESS OF 10. CLIMBING THROUGH 10,000 NOISE SUBSIDED AND DID NOT RETURN. WE RETURNED TO KORD FOR OVERWEIGHT PRECAUTIONARY LANDING. MAINTENANCE REPLACED RT FWD NLG DOOR CONTROL ROD AW AMM 32-22-11.