As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR CONDITIONING DRIVE PULLEY, PN S-3532EC-4 WORKED LOOSE DUE TO EXCESSIVE WEAR TO THE AIR COMM DRIVE RING. THE AIR COMM DRIVE RING, PN 3235EC-5 SPLINES ARE ABOUT 85 PERCENT WORN AND THE T/R DRIVE SHAFT, BLOWER, SPLINES ABOUT 30 PERCENT WORN. THIS PROBLEM WAS FOUND DURING A T/R DRIVE SHAFT REBALANCE. AFTER FIRST RUN SHUTDOWN CLUNKING NOISE WAS HEARD COMING FROM THE DRIVE PULLEY. AIR COMM DOES NOT REQUIRE A RE- TORQUE OF THE DRIVE PULLEY BUT A RE-TORQUE EVERY 300HRS WOULD HAVE BEEN A GOOD WAY TO PREVENT THIS PROBLEM FROM OCCURRING.