I'm a long-time lurker who's found the manual and tech sections here very useful when wrenching on Dad's 860.
The steering has been wonky for some time and as a result the tractor has sat a lot lately, we just pulled the Davis 101 loader off of it and I'm trying to get the tractor in shape for brush-hogging next spring.
The power steering has a single cylinder, with an unreadable label, running from the base of the right axle brace to a clamped-on mount on the right drag link, a divorced-reservoir Ford pump, and a controller fixed to the column on top of a factory steering box. The floppy tie-rod ends in the cylinder linkage allow the whole thing to rotate and bind, this combined with the dubious sector gears in the steering box make for a rather frustrating user experience.
Maybe one of you can put me on the track to find the right bits to tighten up the cylinder linkage? I might well wind up tearing the steering box down before this project is done.