I have recently purchased a 99 E300. Between 65-72 I am hearing a rhythmic pulsating sound that occurs about every second. So if you count, 1001, 1002, 1003... by them time you get to 1, 2, 3, etc. the sound amplifies and then backs off repeating the pattern about at the end of every second.

In addition, at that same time the sound occurs, I feel a vibration coming from under the car. I can almost feel it under the drivers seat all the way to the gas pedal. The vibration has the same pattern as well. I feel it about every second and between intervals it goes away. 1001 - then noise/vibrations....1002 - then noise/vibration, etc.

What is odd is that I do not feel anything in the steering wheel. This noise/vibration pattern occurs both when I am at a steady acceleration or when I take the foot off the gas pedal. I can also assume that the vibration/sound is occurring at lower speeds because once I reach about 40mph and beyond, I notice that the car does not ride as smoothly. However, the sensation is certainly not as noticeable as driving within the 65-72 speed range.

I recently purchased 4 new Michelin MXV4 tires, 4 wheel alignment and balance performed, all 4 rotors and pads replaced, engine mounts replaced, and my mechanic states that he repacked the bearings. The lug nuts were torqued to 100 ft/lbs as well.

The mechanic at the Benz dealership said that in the very near future that I would need some sort of "joints" replaced but I didn't really pay that attention to what he was saying. I know that it wasn't a familiar term, such as ball or universal. Could this attribute to what I am experiencing?

Thank you in advance for your assistance in helping me regain my sanity.