Kyle, I have the same car as you , I would say it is on the noisy side. By this I mean A low motor roar sound . Not vibration , but recently I had replaced the center bearing and carrier and also the exhaust manifold which was bothering me for a while until I found what it was. I like the idle sound of diesel engines , so I would say just check for any heavy type of vibration from underneath the car . The drive components are really noticeable. Lastly I think this motor/vibration feeling is normal. So let that Diesel purr down the highway. Hans.

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A couple of Ford pickups F 150,250, 350 missed.
1983 240 D 256,000 miles ,auto, ac.