As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON RIA FERRY FLT 7104 - KMKE/DTW - A/C RETURNED TO KMKE AFTER EXPERIENCING VIBRATION (4.0 A AND B) ON NR 2 ENGINE AT ABOUT 4,000 FEET. REDUCING POWER REDUCED VIBRATION TO 1.0. UPON LANDING, INSPECTED CHIP DETECTORS AND OIL FILTERS, FAN BLADES, NO DAMAGE FOUND. LUBED MID-SPAN BLADES PER MM 72-31-05. ENGINE RUN-UP ACCOMPLISHED WITH ALL INDICATIONS NORMAL.