If all else fails to solve the vibration pull the drive shaft and check the u-joint. It should be smooth in both direction but rarely is. They usually "wear in" and get stuck or seized with some resistance to flexing in one or both directions and that is the cause of many vibrations. Some people have had luck re-aligning the driveshaft by shimming the center support with washers but that is hit and miss and only masks the problem. The only way to fix it is to have the driveshaft rebuilt and the bad u-joint replaced.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz