What was found
AIRCRAFT WAS GROUNDED: PILOT REPORTS MODERATE AIRFRAME VIBRATION DURING CRUISE. FL260, 157000 LBS, 330 KIAS, WENT AWAY AFTER SLOWING THROUGH 320 KIAS, FELT THROUGHOUT CABIN. ENGINE VIBE LOOKED NORMAL. MAINTENANCE REPORTS RIGGING OF THE BLUE SYS LH ELAVATOR WAS PERFORMED IAW AMM 27-34-00-820-003-B. OPS CHECK GOOD.