What was found
EVERYTHING WAS NORMAL IN ALL PHASES OF FLT, EXCEPT TAKEOFF WHEN GEAR WAS RETRACTED, A GRINDING, OR THUMPING SOUND HAS HEARD, FOLLOWED BY A VIOLENT SHAKING VIBRATION THROUGH PLANE, CONTINUES AFTER TRACTION FOR A FEW SECS & THEN STOPPED. EVERYTHING NORMAL DURING GEAR EXTENSION DURING LANDING & TAXI AGAIN PROBLEM STARTED AFTER NEW TIRES WERE INSTALLED. REMOVED LT NLG WHEEL & TIRE ASSY. AS A PRECAUTION. INSTALLED OVERHAULED NLG WHEEL & TIRE ASSY. REMOVED RT NLG WHEEL AND TIRE ASSY DUE TO EXCESSIVE VIBRATION ON GEAR RETRACTION & LOOSE AXLE NUT, INSTALLED REPAIRED NLG WHEEL & TIRE ASSY. REPLACED MISSING INNER SPACER ON RT AXLE. SERVICED BOTH TIRES TO CORRECT PRESSURE. ALL WORK IAW AMM 32-42-01, AND 12-15-00.