[yoke]

there's a known problem with the intermediate shafts that will cause you to feel the bumps when going slow, and you can hear a knocking up front.

could also be the sector shaft on the bottom of the steering box, where the pitman arm connects. you can see the pitman slide up and down if you jack it up and try to move the wheels back and forth. if you can see the gears on the sector shaft, you can tell if they're worn or if it's the teeth on the pitman arm.

an alignment shop can tell you quickly if it's the pitman/sector shaft or not.