Q: 2004 lincoln ls waht makes the rear end sway

It sounds like you may have a broken or damaged sway bar or stabilizer bar. A sway bar or stabilizer bar is a steel bar that connects suspension components on opposite wheels. Its purpose is to combat body roll when a car makes a turn. It is also known as anti-roll bar, sway bar and anti-sway bar. The spring steel torsion bar is U shaped and is mounted parallel to the ground. The bottom part of the U is attached to the frame with bushings while the ends of the U are attached to the lower control arms of opposite wheel. When a car makes a sharp turn, the part of the bar on the outside of the turn gets pushed down toward the road and the part of the car on the inside of the turn rises up. This is known as roll which happens 10 to 30 degrees toward the outside of the turn. If a car takes a sharp corner at high speed, usually the tires on the inside of the turn rise off the road, if care is not taken the vehicle can flip. This happens as more weight is placed on the outside of the tire and less weight on the inside tires. This reduces traction which in turn interferes with steering. A stabilizer works by keeping the body of the car flat as it takes a sharp corner so that the weight is evenly distributed on all the four tires. Stabilizer bar should be checked for stiffness. This causes side to side motion in the car which affects steering and handling of the vehicle. Failure to maintain sway bars can cause the wheels on the outside of a turn to lose contact with the road causing poor steering and handling of the vehicle. I would suggest having a professional from YourMechanic come to your location to take a look at your vehicle.