I have a 2000 E430 with 50k. I noticed a vibration when reaching speeds of 40 mph (top gear in transmission). This is mostly noticable when cold and seem to go away when warm. I feel it could be the rear-end or drivetrain. Any suggestions?[/align]

 

I have the same car, same year and same problem. Usually when cold and not all the time. Mine does sit quite a bit and I was wondering if it was the tires. I'm thinking of taking the wheels off next time it's cold and having the balance checked.

 

This sounds like a classic case of a bad carrier bearing. The driveshaft is in two parts. Where the two shafts are connected they are held to the body of the car with a bearing and housing that "Carries" the shaft. Hence the name carrier bearing.

The bearing is likely still OK. It is the housing that bolts to the car that seems to wear out first.

Both of these parts are not expensive. It is the labor that is. It is usually easier to remove the exhaust system that to try and work around it.

If you do this yourself then remember: The two shafts are balanced as a unit. Mark the alignment with paint BEFORE removing the shaft assembly from the car. They tend to come apart quite easily.

It is also possible that you threw a balance weight which means you need the shaft rebalanced. If this is the case replace the carrier housing, the carrier bearing and, while you are at it, the shaft connectors at each end of the shaft while you are in there. Remember: The parts on this are cheap. It is the labor that is high so you might as well renew all the parts that are going to need it while you are in there.

Sam