With so many drive line components, in our case at work(four differentials, four drive shafts, eight axle shafts, eight wheel ends, eight road grader run flat tires, two axles that turn, eight variable adjustable nitrogen actuated struts, a transfer case, a Cat C9 engine, and Allison transmission) you have plenty of chances for vibration. The first question I would ask is where do you feel the vibration when operating? (Your feet? Your butt? Or your hands?). Depending on where you feel it is where to start your troubleshooting.