As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
HEARD A MODERATELY LOUD "THUMP" SOMEWHERE BENEATH OUR FEET ON CLIMBOUT AROUND 12,000 FEET, FELT IT AS WELL. THE SOUND WAS SIMILAR TO WHEN YOU CONNECT THE NOSE WHEEL STEERING ON THE GROUND ONLY A BIT LOUDER. REMOVED NOSE STEERING CONTROL VALVE. INSTALLED A MODIFIED STEERING CONTROL VALVE. ADJUSTED FEED BACK POTENTIOMETER AS REQUIRED. CHECKED NON WHEEL STEERING FREE SWITCHING AND NOSE SHADE INFLATION. WORK PERFORMED IAW MM 32-50-00.