I think I'm going to have to break down and take her into a (gasp) - mechanic.
But thought I'd see if anyone here has any ideas:

There's something not right about my steering. Hard to put my finger on, but feels like there's sort of hills and valleys to the resistance when turning.
I had her up and both wheels off today. The only noticeable thing is that when it's 98% to the right there's a sort of clunk that seems to resonate through the whole system. I can move it back and forth through the clunk with a 2º arc of the wheel. And that's the only spot where I get any play when moving the wheels by hand.
All the components seem good, I can't get any play from anything else.
I'm thinking it's the actual steering box. I really don't want it to be, but I think it is.

Side question: when I spin the front wheels by hand when it's running (in park) as soon as I get a little bit of speed up (like 3rpm) there's a noise from the heart of the beast that I can't imagine what is. Sounds like power steering engaging (don't think it is just sounds like it) or a little like the hill descent noise. I feel like there's a slight increase in resistance when it happens.
That's really just curiosity, I have no reason to believe it's not normal.

As usual, thanks!

 

Sounds like the box might be worn out, unfortunately. Did you check all the suspension and steering parts for play? I would probably check that before making a call on the box.
Is the noise you hear when turning one wheel the traction control coming on? Turning one wheel would give it a speed reading that doesn't match the other four wheels.

 

Thanks for that.
Yeah, I checked everything I can. I was thinking hubs for a while, but I think it's the box.
Maybe I'm phrasing the question wrong?
What does a failing steering box feel like?

And I think you are right about the traction control.

 

Have you checked the bolts/bushings on the panhard rod? I'd say it could likely cause the symptoms you describe.

If you still suspect the steering box, I'd adjust the preload/play and see if that helps the situation.

 

Just for completeness - it was my hub after all.

Once I had the old part on the bench I can feel about a 16th of play in it. I think I was expecting more.

 

Cool! That's a lot better than a steering box!

 

Good one, far less hassle and far cheaper than the PAS box but still check the float adjustment in the PAS box which makes all the difference to steering. Screw the screw down gently until solid resistance is felt then back it of 1/8th of a turn and make sure the screw doesn't move by using a screwdriver when tightening the locknut.

 

Ooh. I'll do that. Thanks.