My car feels like it is shaking while driving down the road.

Aaron, my car also does this shake. I have changed tires twice, changed struts and both control arms,front end alignment, brakes and rotors, and still having problems......both my bonne's are doing this shake, also have a friend with same problem and he did his motor mounts too and didn't fix the shake. Can this shake be from a bad rack and pinion? Both of mine are leaking.