As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MKE FLT 3004 - THE CREW REPORTED A BANGING NOISE COMING FROM THE FRONT OF AIRCRAFT ON APPROACH. MAINTENANCE INSPECTED AND REPLACED THE LEFT MAIN LANDING GEAR DOWN LOCK PROXIMITY SWITCH AND CONNECTOR. ALSO REPLACED THE LEFT MAIN GEAR UPLOCK BOX UPPER PROXIMITY SWITCH. OPERATIONAL CHECKS WERE GOOD.