As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) WORN LINKAGE AND PILOT VALVE CAUSED SERVO TO MAKE LOUD GROWLING NOISE. THIS WAS AN INTERMITTENT PROBLEM THAT COULD BE INDUCED BY CERTAIN CONTOL INPUTS. THE SOUND WAS FINALLY DETERMINED TO BE COMING FROM THE RT SERVO AND IT WAS REPLACED. THERE WERE NO CONTROL PROBLEMS ENCOUNTERED AND THE SERVO HAS SINCE BEEN OVERHAULED. (TC NR 20080128007)