assuming you checked tie rods, ball joints, etc. there is actually an adjustment on the stearing gear box that should be able to get most of it out. it's on the top and has a locknut on it. not sure which way to turn it, but the difference is very noticeable. just be a little careful to make sure it doesn't get too tight when the stearing is turned all the way to the lock.
Actually if you want to adjust that screw on top there is a procedure to do that.Its just not as simple as cranking down the screw and tightening the jam nut.Basically you want it to be tighter when the the steering wheel is rotated over center.It should be less than 25inch lbs.without the tirerods attatched and no fluid in the steering gear.