Recently I replaced both front upper control arms, put on new end link bushings, and had the rotors resurfaced. All parts are stock replacements.
Prior to all of this, there was some body roll in the front, and braking caused the steering wheel to wobble hard. Bumps and rough corners caused a knocking or crumpling sound from the RF because of a broken balljoint.
Resurfacing the rotors removed the steering wobble on braking. The end link bushings got rid of some roll, and the control arms have solved some rolling in front as well as the knocking. After the control arms went in, I had an alignment done and the tires rotated.
Now.... it seems the back end is loose, or something is not right. When I hit good sized bumps, the steering wheel jerks hard left or right, and the back end seems to step out. When cruising, the car doesn't pull, but the steering wheel slowly oscillates back and forth an inch or so. The back upper arms seem good, but the lower arms all around could stand replacing.
What should I check? Was this problem caused by stiffening the front and not the rear?

 

Nobody likes me

I don't think that this problem existed before on the car, and I only notice it now. I think something is up. What would cause the rear to step out on bumps? And if it's only the rear, why does the steering wheel oscillate? Maybe my wheels need to be rebalanced?

 

Have you tried getting the car aligned after replacing all these suspension components?

 

My rear end on my 97 Hatch feels the same way. Not sure why yours would just start doing this, but some say buying a sway bar would help.