Symptoms of a dodgy Steering box

my disco has a slight loose knock/play through the steering, alot more when off road than when on.

I have new ball joints for the track and drag but not fitted them yet.The ball joints dont seem to have any play in them but are sheduled for replacement anyway.

the knock/play that I get seems to me, to come from the steering box, i havent tried bleeding it yet, but does this sound like it's gonna need a replacement box or just a bleed???

I'm sure someone will be along soon with some more detail, but I think there is adjustment you can make to the steering box to take up play. But it might not be the steering box causing the problem, it could be the UJs in the steering shaft (between the steering wheel and the steering box).
It might worth taking the steering damper off and checking that it is working ok and replace if not.

Thanks Richard, it's recently had a new damper and a new steering shaft so i reckon i can rule those out for now...