As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: PILOT REPORTS FLAP RETRACTION AND EXTENSION, BETWEEN UP AND 1 GENERATES A LOUD GRINDING NOISE. SEEMS TO BE ON LEFT (CA) SIDE OF ACFT. INFLIGHT ONLY. MAINTENANCE REPLACED THE LT T/E FLAP OFFSET GEARBOX IAW AMM 27-51-38-401. OPS CHECK OK.