of the three adjustment points on the 2 tooth steering box, which is for adjusting the back and forth play or the steering wheel left to right play?
Fordbarn Model A forum is the place to be! That is one job I have yet to do on Model A's, rear ends now that is a different story.
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The adjustment is a bit complex, involving incantations and sprinkling of magic dust.
Oh, not buying that one, eh?
OK, two adjustments must be made first, end play on the sector shaft--the screw and lock-nut on the side of the box does this. Then there is the end play of the worm. Now here it DOES get a little messy, the entire box moves around on the sector bearing piece (the part that's bolted to the frame). If the sector is too tight on the worm, it will not allow you to adjust the worm bearings, so make certain that's too loose so as to not effect the bearing adjustment.
Now the worm is designed to be tight when in the straight ahead position and have some looseness when at the ends of the worm. There are four bolts holding the assembly together, and one slotted pin. The slotted pin is offset, so turning it one way brings the gears closer together. the far bolt has a three-part nut, one is a cam action, inside it is a tapered cone, and then the nut itself that tightens on everything, so you also have to adjust this end until you get no play at the center and an equal amount of play at each end of the turning stops.
See why I mentioned incantations??
Once you've done it a few times, it doesn't seem so difficult. Be sure and keep lube in it!
This is a follow-up to David's excellent advice. Unlike Model T steering units, lube, yes; grease, NO! Too many guys think that the zerk fitting in the steering box is for pumping in chassis grease. Nope! In Ford garages, this fitting was used to pump in very thick lube, like 600w. The design of the Model A steering boxes (both seven- and two-tooth) needs fluid lube, thick clinging fluid lube. Chassis grease is soon squeezed out between the worm and the sector teeth, resulting in rapid wear and hard steering. Of the many Model A steering boxes I've restored over the years, the ones that had grease packed in them were the ones with the WORST wear patterns on the sector teeth. Once that happens, there's no way to adjust out the slop at the steering wheel. The sector and worm gear first need to be replaced = $200+, plus new sector bushings that MUST be reamed for the new sector shaft. The upper and lower bearings are usually ruined, too, due to lack of lubrication that grease cannot supply. There are better lubes available for the steering boxes than 600w, including Penrite, which reportedly isn't as prone to leak. But whatever you do after you get your Model A steering properly adjusted, please do NOT pump grease inside!
Model A's since 1966, Model t's since 1978