What was found
SUDDEN SEVERE VIBRATION AT 26K FT, 320 KTS PILOT TURNED OFF AP, THROTTLES TO IDLE, MOVED FLT SURFACES, NO HELP. SLOWED TO 280 KTS, TURB STOPPED. ENTIRE ACFT SHUTTERED. PILOT REPORTED SEVERE VIBRATION STARTED & STOPPED SUDDENLY, NOT GRADUAL. NO MACH TUCK REPORTED. ACCOMPLISHED ELEVATOR SERVO ADJUSTMENT IAW AMM 27-34-00, ELEVATOR & RUDDER FREE PLAY CHECK MM 27-34-00. REPLACED AFT NOSE GEAR DOORS & ROTATING RODS & WORN PARTS.