What was found
CLIMBING THROUGH FL300 AT APPROX .68M WITH AUTOPILOT ON, A SIGNIFICANT VIBRATION BEGAN IN BOTH CONTROL COLUMNS. AUTOPILOT WAS DISCONNECTED & THE VIBRATION CONTINUED. WE LEVELED OFF & SLOWED & THERE WAS NO CHANGE. WE BEGAN A DESCENT & THE VIBRATION SUBSIDED UNTIL APPROX FL270. IT CONTINUED & WAS FELT IN THE CONTROL COLUMN & RUDDER PEDALS UNTIL APPROX 8000FT & 230 KIAS. FROM THERE TO LANDING ALL CONTROLS FELT NORMAL. THE FLIGHT ATTENDANT FELT THE VIBRATION IN THE FLOOR OF THE FWD CABIN. A PILOT SITTING IN SEAT 12B NOTICED AN AIRFRAME VIBE. ACCOMPLISHED VIBRATION DVI IAW WC 12-200-01. NO DEFECTS NOTED AT THIS TIME. FCF FOUND SATISFACTORY.