Driveline Vibration - 700/900 Series
Vibration or Knocking Sound Under Acceleration
Tools/Supplies needed: 3/8” rachet, metric sockets, about (20) 5/16” cut washers
If you have felt a strong vibration, or heard a knocking sound from the mid-floorpan area while your car was accelerating, you probably have a driveline alignment problem. (This can also occur with proper driveline alignment but with the car so heavily loaded that the back is squatted down causing a temporary alignment problem.) Occasionally this will occur after a car has been lowered with a sport suspension system.
To correct, you need to alter the height of the center driveline support. This will change the driveline angles and reduce the mis-alignment. If you suspect your car is lower in the rear than factory specifications, you need to shim up the center driveline support. If you suspect your car is higher in the rear than factory specifications, you need to shim down the support tray (that the driveline support is fastened to). Note: some models have support trays that are welded to the body structure and therefore the center bearing can only be moved up.
The most you should change the bearings position is 1/2” (12mm) upward, or 3/16” (5mm) downward. Just add some flat washers as shims to the anchoring bolts. Consult illustration.
To raise the mount, place washers between the rubber mount and support tray (2 positions).
(Most likely for cars with lowered springs).
To lower the mount, place washers between the support tray and the body (4 positions).