Hi Twillo, I may have a solution for you problem. I drove a GLA 45 AMG here in Switzerland which had the same issue as you are describing. Let me try to explain what the issue was on my car. The driveshaft which connects the front drivetrain with the rear drivetrain has three shafts which are connected together, and these shafts have to perfectly balanced. The balancing process is done before the car gets to the assembly line. So when the car is in production, these shafts have be put together the same way as they were on the end of the balancing process. For this reason they also have markings. The mechanic who done the repairs on my car, explained, that one of these shafts was twisted 120 degree of the correct position (I guess there is a total of three positions 360/120). Therefore the entire shaft assembly was out of balance and this is what caused the vibrations on my car at higher speeds. Hope this helps, please let me know. Good luck and best regards George