How is the condition of your tires?
As I said in my first post the tires are new and even the rims were checked...and the balance of the wheel was double checked in two places.
...Why not take it to a mechanic to have him diagnose it?
I was with the car at a few mechanics...(I did not made the jobs that I described in my first posts...the mechanics did). I have speak with the representant from Mercedes Romania, the chief engineer of mechanics, but even him did not give me a good tip that resolve this annoying problem.
The car was put to tests in two "stands" and everything was just perfect. I have made the shock`s test and they were all good. At first test the difference between the shocks were 1% in the front and 2% in the back. Just the efficiency was a bit low :50-51% front and 37-39% rear.(I have attached a scan of the test results)
At the second test in a new location the efficiency of the shocks was an average of 75%.
There are a lot of things that cause such vibration : rings, tires, axles, drive shaft, drive shaft central bearing, flex disc etc...
You are right! There can be numerous reasons and I (or the mechanic) have tried all of that: rings, tires, axles, drive shaft, drive shaft central bearing, flex disc...and even more: engine mounts, gearbox mount, shocks, undercarriage, etc.
Just that there is something that is slipping to us or the checks were not good enough to find a problem.
To be precise
...How did you get this problem, just all of a sudden? or is there some thing went wrong before that?...
: I have hit a pretty big hole in the road in Hungary at 90-95 km/h the day before...but after that I have made a few hundred kms on the highway without problems. The vibration had started when I have arrived near Vienna and the highway started to get bad, made from concrete and with uneven joining of the surface. It was the place where the vibrations started!
The strange thing is that if I go in bad roads the vibrations are not present, or they are overwhelm by the moving of the car`s body.
In the way back home, in Hungary-where the particularly bad roads are present everywhere, I did have no problem going even with 100 km/h.
Only when the road is smooth the vibration is feeling so strong that the car shake violently.
...Most of the vibration comes from the rings and tires, check and/or do tires balancing, also take a look at the diff mounting bolts with its rubbers.
All of this were checked and declared OK!
You may not need all what is being done so far.
Absolutely right! Nothing has changed since I have made those changes...