Hydraulics conked out and I found all the Hy-tran in the crankcase; Boss kindly rebuilt my hydraulic pump, I put it back on, flushed the the bit of remaining oil from the TC block (with Hy-tran), refilled the TC, bled the air.
The pump is perfect -- the hydraulics work flawlessly when raising, nice and tight. However, they lower very slowly -- maybe 4 seconds for full travel. And it sounds like there is an increased engine load when lowering, but no added load on the engine when raising. This is all with no implement attached.
When I refilled the TC block after bleeding the system, the oil that overflowed out was lighter-colored, like it was mixed with some air? Perhaps normal, maybe not.
I'm looking for thoughts on how to proceed.
Since I got it, the cub smoked some and had (I thought, anyway) weaker/slower hydraulics, though they worked the same in each direction. It made sense that Hy-tran was getting into the engine, thinning the engine oil, and weakening the hydraulics. I brought the cub home with a tobacco transplanter and cub mounting brackets, hooked that up in the way it seemed would take least power to lift, but even so the hydraulics couldn't handle it. At this point I bet I dealt a final blow to the pump, whatever condition it was in beforehand. It's possible I ran the system some with low fluid -- I don't know at what point the rest of the Hy-tran went into the crankcase.
The pump is now fine. I looked at the TC troubleshooting procedure, but there wasn't anything about it being hard in one direction only. What would cause this issue? I'm guessing something's up inside the TC block, but what? Could lifting too-heavy a load hurt the TC block? I would guess they'd design the system so that the pump just wouldn't take the load, saving the TC block from harm...and it has safety valves too right?
Also -- this may be important, I just thought of it -- the TC block sat empty of oil for a month or so while the pump was rebuilt, and I didn't cork the hydraulic line holes, I just covered the thing with plastic so nothing would get inside. Could something have gotten a little rust? Or grit DID get inside, but there's a filter for that, right? Or an issue with the hydraulic cylinder itself, going out easily (raising) but meeting resistance going back in (lowering).
Thanks for your thoughts here on narrowing down my problem.