As said, first check for loose tie-rod ends. Have someone wiggle the steering wheel (with the engine off) and feel all the ends of the tie rods and drag links. If everything's tight, you can adjust your steering box. I just got done doing this. On the top of the box, there's a 5/8 jamnut with a 3/16 allen screw in the middle of it. Center your steering wheel, loosen the jamnut about a half-turn, and while holding the jamnut still, tighten the allen screw until it just barely bottoms out (don't force it; you can damage the gear. ) Then, still holding the jamnut, back off the allen screw about 1/3 to 1/2 turn, then tighten the jamnut while holding the allen screw still with the allen wrench. There has to be just a minute amount of "slop" to allow the steering gear to auto-center while driving, but it should take a lot of the play out.