Rear end swing when hitting bumps

[LazSlate]

Shocks. Bad shocks will rebound to quickly causing loss of traction and jarring.
Its not sway bars as those control roll and linkage and parts you would hear noises and notice crappy handling all the time. You can jump up and down on your rear bumper then jump off. The oscillations should stop immediately.

 

[Bmac1955]

Do you have this in writing, that you can share. My dealer is telling my that fronts are not covered under esp warranty

This what I found for Ford ptotect warranty regarding rear suspension warranty.

 

[mr_dave]

Fronts and rears are both definitely struts, by definition. Whether or not Ford wants to honor the wording in their contract is a different issue.

The behavior you describe is mostly likely caused by a bad strut on the rear. I've experienced this on several vehicles and fixed most of them with new shocks/struts. However, one vehicle actually had a bad spring in the rear which also needed to be replaced, so it could be that too. Or even a broken (or very loose) part of the rear suspension.