The steering box is not really adjustable. The nut and screw located on the top of the box will adjust the preload on internal parts. Binding will occur if there is insufficient clearance between the worm and roller gears, as you have described. The first things to check are the tie rod ends, steering column universal joint and the connection between the upper and lower steering shaft(located inside the firewall between the clutch and brake pedal) It is common for the output shaft bushing in the steering box to become worn and allow for the shaft to move from side to side within the box. The only correction for this problem is to have the steering box rebuilt and the bushing replaced. I had mine rebuilt by Benchworks Steering in Scottsdale AZ, 1-480-946-3992....Problem solved.