We have three OBS trucks and only one really steers well. I researched this and found that Ford in its infinite wisdom decided to machine the sector shaft race right into the steering box housing. The housing is cast iron - not nodular iron like 6.7 blocks - just plain old cast iron. So the sector shaft bearing wears the iron and eventually you get a slightly egg-shaped race in which the sector shaft's bearing rides.

Even at a good shop like NAPA, they only offer rebuilt steering boxes, and that lower bearing race is the same one that was turned in to get rebuilt. It's not machined because that would just make it too big overall. What this means is that you buy yourself a "brand new rebuilt" steering box that already has radial play in the sector shaft. This translates into play in the steering. Here is a video of my "new rebuilt" steering box and the radial play.
It only gets worse, and sooner or later that radial play destroys the lower oil seal. Then you get leaks. Or maybe the steering box starts to get sticky such that steering is difficult to moderate. Cops behind you might think you've been drinking. If you attempt to tighten that play out, you can't. You can only adjust axial play, with the adjustment on top of the steering box. Applying more pressure there will just make the box get too tight. And wear out quicker.

The answer is to get a steering box rebuilt by a shop that installs a new bearing race down there. There may be others but I'm only aware of Red-Top and Blue Top. Both have good reputations here in the forums, but of the two, Blue-Top has a lower price and faster turnaround time. So that's who I'd recommend if you want to finally fix that sloppy steering box in your OBS.

https://www.bluetopsteeringgears.com/
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I've used Blue Top, owned by Ryan out of North Dakota, not Red Head out of Seattle. Agree, Ryan from Blue Top has a stellar reputation with the Dentside (73-79) F-Series truck owners. I got mine Blue Top steering box about 2 1/2 years ago and my 77 F-150 steers like it was new. Ryan's (Blue Top owner) worked for his cousin who owns Red Head, Ryan decided to branch out on his own. If you call Blue Top, Ryan answers, good old school customer service.
Don (EQCMCAT)

 

Exactly what I got. The owner answers the phone! Man I'd kill for that kind of service at some other shops I work with ....

 

As I watch your video, and I watched it several times, it looks to me like the play is in the splines. Maybe it just looks that way to me. Either the splines on the steering box or your pitman arm are worn or the nut isn't tightened. OR maybe it just looks that way to me.

 

Now you got me. I'm going out there to check!

OK, I'm back. That nut was not on there as tight as I'd like it to be, but it wasn't loose. About 1/8 of a turn is all I got. Now the play in the steering is ...still the same, dang it.

 

I noticed the exact same thing on my 5 y/o rebuilt box a few weeks ago.
I have a drop pitman arm and over size tires, so it places even more strain on the sector shaft.

When it gets to the point that the seal leaks, I will be going with Red Head, as I am local to them (no shipping!).

I believe they take care of the sector shaft bearing tolerances.

 

Blue Top
Red Head
Cool.

 

I have had a RedHead in mine for 4 years with zero issues (ballpark 60k miles). I don't recall the price but I did buy during a forum group-buy program/promotion to save some.

 

Swapped in a bluetop and borgeson shaft, nice and tight.

 

I was going to put a Flaming River shaft in my Bullnose, but they were so snotty on the phone that I changed my mind. The Blue-Top guy is a real gentleman. Borgeson, you have to cut it to fit, right?

 

Yep, measure, then cut it with a hacksaw, takes all of 5 mins.

 

The horror .... Well, I bought a rebuilt shaft off fleabay and so far so good

 

My old box had lost all of it's hydraulic assist, it was rough.