Preliminary Diagnosis: Tires
WARNING: This page is about a different car, the 2006 Mercury Montego, 2006 Ford Freestyle, and 2006 Ford Five Hundred. However, it is still accessible from the selected car via links, so may be relevant.
WARNING:
Do not balance the wheels and tires while they are mounted on the vehicle. Possible tire disintegration/differential/halfshaft failure could result, causing personal injury/extensive component damage. Use an off-vehicle wheel and tire balancer only.
Most vibration in the rear end is caused by tires.
Vibration is a concern with modern, high-mileage tires if they are not "true" both radially and laterally. They are more susceptible to vibration around the limits of radial and lateral runout of the tire and wheel assembly. They also require more accurate balancing. Wheel and tire runout checks, truing and balancing are normally done before axle inspection. Refer to WHEEL AND TIRE .