steering boxes that have a worm gear
there is a fine adjustment screw, that is held in place with a lock nut
there is also a course adjustment screw, also held in place with a large lock nut
first find the center of travel by counting the turns from right to left & left to right
split that number in half to find center
Look at the steering box closely for a small screw with a locknut, if there is one, it has to be backed off just a bit
Then, Loosen the locknut on the pitman shaft adjuster screw Make sure the adjuster screw is held and does not turn with the locknut
Turn the adjuster screw in approximately 1/8 of a turn. While holding the adjuster screw, tighten the adjuster screw locknut.
If was a smaller adjustment screw, turn it down until it bottoms out & then back off about an 1/8 of a turn, lock it down using the same method as mentioned above
Now test the amount of play, if it feels good, test drive it
This illustration may explain it a bit better
from another forum
16mm Open End Box Wrench
4.5 or 5.0 hex key.
Maybe some Brake Cleaner for the dirty ones
If the box has dirt and other debris on it you are going to want to spray the box down with brake wash to remove most of the dirt. Make sure you clean the top of the box.
On the top of the steering gearbox you will see a large bolt located on the top near the middle. This is the 16mm bolt that you will need to lossen.
Insert the Hex Key into the top of the nut and point it to wards the front of the truck. Then loosen the 16mm nut about 1 or 2 turns. Keep the hex key pointed to the front.
Either have another person sit in the truck and wiggle the wheel back in forth while you tighten the screw or get up and down a lot to take up the play. You should only adjust the screw about a 1/4 turn at a time. A 3/4 turn will roughly take out 2 inches of slop. Don't tighten the hex too tight or it may cause damage to the steering box. The steering should be tight but not so tight that when you are finished that you have to muscle the wheel.
After adjusting the screw. Hold the hex in the position where you adjusted it and tighten the 16mm nut. Nice and snug. DON'T OVER TIGHTEN.
Start the truck and check for any leaks. Test your steering see if you still have play. If so you can repeat the steps to get rid of most of it.
Further explanation of the adjustment, so you may be able to picture it in your mind
This part of the post is also from that same forum
These are Saginaw steering boxes, designed in the 60s. What you're actually doing is adjusting the backlash (i.e. tooth clearance); much like setting up a differential gear assembly (Ring/Pinion) after a rebuild/replace/whatever.
The plate under this nut you're loosening is called a 'top plate adjuster.' This nut determines the backlash between the power piston teeth (what the steering column/shaft connects to) and the sector shaft teeth (what the pitman arm connects to), and thus, the return to center characteristics of the steering. By adjusting this, you will be able to get back most of the stock characteristics of the steering. Improperly adjusted, you risk the chance of binding/disengagement of the teeth due to improper backlash.
It's DEFINITELY not something to take lightly, as it is the steering that we're dealing with, here.
Basically, the sector shaft has tapered teeth (3); wide at the top (closest to the adjuster nut) and narrow at the bottom (closes to the pitman arm.) The power piston teeth are not tapered, but are widely spaced.
When you adjust the allen at the top of the box, you're moving the sector shaft up and/or down, changing the clearances of the tooth mesh, or backlash.
Too far down, or tight, and you force the sector shaft teeth to power piston teeth, causing binding to occur. This results in an oddly tight steering response, binding, lack of RTC (return to center), and possible breakage of steering components within the box.
Too far up, or loose, and you increase the sloppiness in steering response, as well as risk possible disengagement of the steering teeth, resulting in no steering control.