If your car squats and rises noticably, then you probably need to check a couple of things but more than likely your rear differential mount is in need of replacement. Is your car sitting a little low in the back?
This mount is a u-shaped mount on the rear of the differential. It is bolted to the chassis and has 2 bolts that hold the differential. Wear of this is not easily verified visually, but squat/rise is a dead give away. It easily replaced, be sure to have a jack under the diff. when you do it.($50)
Also, another thing you should check are the sub-frame mount bushings. These are located at the front of the trailing arm where they bolt to the chassis. (large at least 4-5" across)
I changed both of these out earlier this year and was very pleased with the handling improvement. Also the car now sits higher in the rear. I am not sure why but it seems the height of the rear has even improved a little with time.
(The old sub-frame bushings also make great jack pads. Remove the existing cradle on a floor jack and insert a bolt through the bushing.)
