I'll definitely check the play when I get the seals out, hopefully tomorrow.
The rockshaft does have about 1/4" end-play, which obviously would be hard on the seals. That's apparently controlled by the lift arms, and I'll clean up the shaft ends (seal surface and splines) and lift arm splines when I get them off -- they might slip on further. Should I stick some kind of shim between the housing and arms?
These hydraulics haven't worked since I got the tractor, so I don't really know what I'm getting into. But the internals looked good, over a year ago. (I even found a new gasket!)
I just got the pump sorted enough to give the lift arms an erection, with only dripping leaks from one lift arm. I don't know yet whether it has proper power, though. The pump did feel good and tight when I spun it in my hand. (Tractor is manual steering, but pump has the power steering circuit. Dunno.)
I haven't purged the pump, and it's cavitating real bad (foamy oil). It was sucking air at the return line, but I got those new seals in last week, and no leaks yet.
I trying to say that I want to fix the lift arm leak before filling it right. (I don't know how to drain it either, without making a big mess.)