As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB AFTER FLAP RETRACTION, AN AIRCRAFT VIBRATION WHICH SEEMED TO FOLLOW NR 1 ENGINE RPM WAS FELT. AIRCRAFT RETURNED TO MSP. GROUND MAINTENANCE INSPECTION OF AIRFRAME REVEALED NO DISCREPANCIES. NR 1 ENGINE WAS GROUND RUN AND FAN TRIM BALANCE WAS PERFORMED. AIRCRAFT RETURNED TO SERVICE.