Guys so I'm back working on this tractor but have still not found a resolution yet. First off it's actually a 4600 not a 4610 but still same 201 Diesel engine. We have now adjusted valves which were found to be in spec. We have done a compression test on all 3 cylinders. All are were well in spec per Ford specifications. Injectors were replaced. Fuel filter replaced. Timing was found to be advanced to 7 or so. Apparently someone has been monkeying with it in the past as Ford spec says to start at 0. Seems have more power and smoke less now but the vibration still exist between 1600-1800. Also we put in new fuel shut off valve in fuel tank. So now I'm out of ideas. Anyone have any thoughts as to what could be causing the issue? Also it's engine related as it does it in gear or out of gear. Causes stuff to shake and vibrate badly on the tractor and is very annoying. Thank you