I am looking into purchasing an early 2004 2500 CTD with 89000 miles. I test drove this truck CTD today and it is a very nice truck with the exception that it has a vibration/buzz at about 1800 RPM, as soon as you get up to highway speed. You can feel it in the gas pedal and slightly in the floor board, kind of what a slight wheel bearing issue would feel like, although I noticed that it is RPM specific. What I mean is that every time you get into the 1800 RPM range whether it is 2nd, 3rd, or 4th gear it has this "buzz". Slow down slightly or speed up slightly and it goes away.
Anybody with any ideas?
THNX

 

I would guess you have a heat shield loose or something like that. I don't know of anything that would cause a buzz that would be detrimental to the engine. Check the clamps on the injector lines, those seem to be a major cause of noises on these trucks.

 

Hard to figure, might check the fan for any damage. Could be a bearing on the front of the engine driven by the belt. It could be coming from the clutch if it is a manual.