What was found
ON DEPARTURE (200 KTS GEAR UP FLAPS 0), A LOW FREQUENCY VIBRATION WAS FELT THROUGH THE AIRCRAFT, BOTH FLIGHT DECK AND CABIN. VIBRATION WAS NOTICEABLE ENOUGH TO SHAKE SEATS SIDE TO SIDE, ENGINE FAN VIBRATION 0.2 AND 0.5, SMOOTH AIR FLIGHT CONDITIONS. CHECKED COMPLETE AIRCRAFT AND FOUND ALL FOUR HORIZONTAL STABILIZER BUSHINGS (WHICH HOLD STAB ON) SLIGHTLY WORN. BUSHING REPLACED AS PER SB 601R-55-007 PARTS A & B ONLY. OVERSIZE BUSHINGS NOT REQUIRED IAW SB, STANDARD BUSHINGS INSTALLED. AIRCRAFT TEST FLOWN AND COULD NOT REPRODUCE DEFECT.