As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS BROUGHT TO MAINTENANCE AFTER A TRAINING FLIGHT WITH REPORT OF A SEVERE NOSE WHEEL VIBRATION. AN INSPECTION REVEALED THAT THE END OF THE SHIMMY DAMPENER BARREL CLOSEST TO THE SERVICE HOLE WAS BROKEN OFF. THE OUTER RETAINING LINE AND BEARING HEAD WERE MISSING.