Power steering box question?

[myyamr7]

My 71 c10 seems to have a bit more than normal free play in the steering, just wondering if it can be adjusted out with the allen screw on top of the box? If I recall, the manual steering boxes you were able to adjust out the free play in them.
It's not extreme, and not really an issue if the road is in good condition, but older roads where there is a crown or something, it seems to drift with the change in road surface. Or even changing lanes on the freeway?

Thanks