What was found
(CAN) DURING CLIMB OUT AT 800 FEET ALTITUDE THE ACFT SUDDENLY STARTED TO SHAKE VIOLENTLY. THE PILOT ABORTED THE CLIMB, PROCEEDED STRAIGHT AHEAD FOR 4 MILES TO A LANDING STRIP AND LANDED SAFELY WITH NO INJURIES TO PERSONS ON BOARD. UPON INVESTIGATION AS TO THE CAUSE OF THE SHAKING IT WAS DISCOVERED THAT THE CLEVIS END P/N C4CM1956-11 HAD PULLED COMPLETELY OUT OF THE SCREW DRIVE P/N C6CTM1028-27 IN THE ELEVATOR SCREW JACK ASSY P/N C6CT1010-3. THIS ALLOWED THE TRIM TAP TO FLUTTER WHICH IN TURN CAUSED THE ELEVATOR TO FLUTTER INDUCING A VIOLENT SHAKING OF THE ACFT.