What was found
NLG VIBRATION AFTER RETRACTION, AFTER START AND DURING TAXI NWS OPERATED NORMALLY. TAKEOFF ROLL AND ROTATION ALSO NORMAL. RAISED THE LANDING GEAR AND IMMEDIATELY HAD A VERY PRONOUNCED 2 PER SECOND VERTICAL VIBRATION AND LOUD THUMPING NOISE. IT FELT LIKE THE NOSE GEAR HUNG UP IN THE WHEEL WELL. AFTER 5 SECONDS, EXTENDED THE GEAR AND VIBRATION AND NOISE STOPPED AND DISPLAYED 3 GREEN. RETURNED FOR LANDING WHICH WAS NORMAL. AIRCRAFT TAXIS NORMALLY. NOTICED A WOW MISCOMPARE CAS DURING THE EMERGENCY RETURN. NO DAMAGE FOUND ON POST FLIGHT. FOUND NOSE GEAR STRUT TO BE UNDERSERVICED. SERVICED THE STRUT IAW MM 12-20-15. PERFORMED MULTIPLE GEAR SWINGS ALL OPS CHECKED GOOD.