Erik, I haven't figured anything out specific although I suspect that it was related to the hydraulic fluid. Since my original post, I have changed the fluid (changed the filter, clean the screen, etc.) a couple times and with each change, it has gotten better in that the PTO does not stop under a load anymore like it was doing. In other words, it is working like it is supposed to. I have always used the JD Trans fluid so I will continue to do so and will change regularly. The stuff is expensive but still cheaper than tearing into it or taking to someone else to fix. Maybe I lucked out (didn't have to dig into any further) and that is all it needed . Fingers crossed.