As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF: WHEN RETRACTING FLAPS FROM 18 OR 13 DEGREES TO SLATS/0 DEGREES THERE IS A SHUDDER. THROUGH THE ACFT THAT FEELS LIKE A HYD PROBLEM NOT A FLAP POSITION AERODYNAMIC ISSUE. ONLY OCCURS WHEN RETRACTING 18/13 DEGREES AIRBORNE. INSPECTED FLAP/SLAT SYS AND CYCLED SYS THROUGH FULL OPS RANGE. NO DEFECTS NOTED ON GROUND. OPERATED LT AND RT HYD SYS ON GROUND, NO DEFECTS NOTED.