If it's like my 10K you'll get significantly lower pressures with warm oil, especially back at the steering clutches. I couldn't make much sense of the readings I was getting on mine until I was able to get it inside a heated shop and run it until pretty well warmed up (25-30 minutes) and hook gauges to all test ports.
I've been fighting the same problem with mine, working on it on/off most of the winter. Been checking pressures at all the test ports (I think there are 10-12 check ports)
My biggest problem was leakage at the steering clutch seals. If I blocked off the tubes back on the bevel gear case I got decent pressure (still a little below spec.), but with the tubes open to the clutches I was losing nearly 100 psi when the clutches were released. I pulled it all down and replaced not only the seals, but the bearing cages and hubs to be sure I had everything good. Before I put it all back together I test ran it with the covers off the bevel gear case to see what the pressures did......gained maybe 25 psi and was still gushing oil through the clutch seals.
The problem with mine came down to the seals (genuine Cat).....They are a split ring seal and they leave about an 1/8" end gap on the ring which allows a lot of oil to leak through. That might be ok for a new tractor, but for a 40 year old machine with wear everywhere in the hydraulic system, it just couldn't maintain pressure.
I thought about it for quite a while and finally decided to make my own seals. I bought a sheet of Teflon (PTFE) material and turned out seal rings on my lathe and milled them to thickness to match the Cat seals. I left the seals full circle, which makes them a little tougher to assemble, but I was going for no leakage. I probably could have split them and just fitted them with a close end gap and it would have been just fine.
I rented the hydraulic puller for a 2nd time ($125 each time) and installed the homemade seals. This time when I checked it there was no visible leakage and my clutch pressure will come up to the same reading I'm getting at the steering clutch valve. At least now any low pressure reading I'm getting aren't related to the clutches and just today I've pretty well got it all back together.
As I said, my pressure at the steering clutch valve is still a little below spec, especially at low idle, but I can chase that problem without having a major tear-down. My trans pump is in good condition and I have good pressure at the sequence valve.
I've got two things that still may be losing pressure......The steering clutch by pass for lubing the bevel gear bearings seem to flow an excessive amount. (If you remove the rear cover plate you can see the amount it's flowing)
The 2nd possibility it the transmission relief valve.....it's bypassing quite a bit oil when the engine is warm. Talked to the Tech at Cat and a couple of the mechanics but couldn't get a definite answer about what's normal.
Her's what my clutch leakage looked like:
https://www.youtube.com/watch?v=ArhkfCFQlGU
Here's the bypass at the trans relief valve:
https://www.youtube.com/watch?v=1ScFPuHgh4U
Here's the view through the back cover:
https://www.youtube.com/watch?v=j475kwoWYQM
The stream that's up by the trans pto shaft is the lube bypass
The stream nearer the camera is the port that dumps oil from the clutches back to the sump. (notice it flows some all the time)
Anyway, I don't know if any of this helps but at least you might compare what I'm seeing with what you see on your tractor. I'd be especially curious to know how your trans relief valve and steering clutch valve compare to what my videos show.
Hope you have an easier time getting your's figured out......mine has turned into a "quest" to get it sorted, but I think I've got it to the point where it's "ok" for now at least.
