P&S, I appreciate the explanation, clarification, and suggestion. OJT is something that there is no substitute for. I tried to locate some sort of spec on what the flow from the case drain should be but could turn up nothing.
You are quite correct in that the only way to replace the pistons (in particular) is to buy the output shaft. The pistons are held in place by pressed in rings on the end opposite the cylinder. If I had to, I could build the tooling needed to remove and replace them, but they are not available as separate items.
Since you obviously are familiar with these motors, let me ask about the solenoid mounted on the valve segment end of the motor. Which direction is the normal operating position, "up" or "down"? Or is this F and R? I realize this changes the displacement and hence the flow, but the machine this is going on has been really cut up as far as controls, wiring, and lots of hosing. Assuming the solenoid is not ever energized, where does that leave the valve segment? I would not think it should just float. Or is this something that is (or I should say ought to be) normally switched manually from the operator position? It does have the connector and at least that part of the harness, but of course, following it back to the control is practically impossible. I can get power to it if needed, and switch it if that is required or desired. I suspect that one of the rocker switches on the panel did control it. Also, the nut that I imagine held the coil in place is gone, so if it is intended to be reversible, that's not possible at present and I'll have to make a nut. I'm learning that getting parts for this Hydro Ax is nearly impossible.
I've been warned about the dogbone and reassembly, and that if I call this particular service manager he will give me some tricks, but I can see that it will be awkward, to say the least. I see a bit of frustration in my future.