Researching for possible answers to my own problems with 580B power shuttle and came across this. New to site and have no real experience with posting, etc but will give it a try anyway. Curious about your problem and looking at the detailed drawings included in my factory service manual, Section 162, How It Works, Torque Converter with Rockford Power Shuttle, Figures 4 and 5, the Clutch Piston can either travel in one direction for forward or the other for reverse, not both. It does not seem possible to bring pressure against both forward and reverse discs at the same time. How did this all turn out?
My problem has to do with very little torque reaching the wheels when cold. I let the engine run a bit to warm up. I'm also engaging the shuttle in forward or reverse with the transmission in neutral to circulate oils and warm that up a bit as well. It helps but it's not the answer to the problem. Starting with light use it gets better with ten to fifteen minutes of use and within a half hour I get good engagement.
At first I suspected the power shuttle clutches but if they were bad, I don't think they would become more effective with time time. My focus is now on the torque converter. Thinking fresh oil and filter might help things a bit I changed both but draining I only got about 12 quarts which is way short of the published 16 quart capacity. Same on refilling, at 12 quarts I was about 3/8" above the mark after running a bit and purging the air. Hard to believe but could the mark be wrong?
I always keep the oil at (or above) the mark. Yes, it fluctuates depending upon how long since last run. I believe the torque converter is draining between uses. Start it up and run a little and the oil is where it belongs. Anyway, maybe it takes some time to work all the air out of the torque converter and so it is operating at reduced efficiency.
Hope I'm not too out of place with my comments. No offence intended. I'm old but willing to (try to) learn. I've had this tractor for about 20 years and have gotten a lot of good work out of it. It's old too. I'd like to keep it going.