As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE CREW REPORTED IMMEDIATELY AFTER TAKEOFF FROM CLE A LOUD REPETITIVE THUMPING NOISE FROM UNDER THE AIRCRAFT. MOMENTARILY THE LEFT MAIN GEAR INDICATED AMBER CROSS-HATCHES WITH A MISCOMPARE INDICATION ON THE COCKPIT EICAS. CREW PERFORMED AN AIR RETURN TO CLE WITHOUT FURTHER INCIDENT. MX TESTED WIRING AND REMOVED AND REPLACED THE LEFT MAIN LANDING GEAR UPLOCK BOX. ALL OPERATIONAL CHECKS WERE GOOD.