Update: First, I ordered a test gauge for the main hydraulic pressure, that which runs the front implements. It came with shims, in case an adjustment was needed. Pressure was about 50 pounds below the minimum threshold. Easy fix with shims.
Second, I ordered a gauge that goes up to 300 lbs for the clutch circuit, and stopped by my local Kubota dealer for a hose and an adaptor. Clutch pressure should be between 150 and 180 pounds per the manual. It is at about 45 lbs.
Which leads me to think the PTO clutch relief valve has an issue. Problem is you can't get the thing out without dropping the engine.
Digging around on youtube I found a vid where the guy notched out the frame to get to the valve. It was clogged. He cleaned it and put it back, issue fixed. I'm considering trying that, but thought I'd come back to the group for advice before hand. Thoughts?
One more comment. I mowed two days ago and paid particularly close attention to symptoms. Recapping and adding more:
1) The PTO starts off when it is cold just fine. Engages quickly, no bogging. 5 minutes or so into mowing . . .
2) Slightly heavy grass the blade speed slows down. Reconfirming, the driveshaft is slowing down. the belt is not slipping, the engine maintains speed.
3) Mowing downhill the blade speed slows down.
4) Level ground and uphill, the blade speeds back up, until you hit heavy grass.
5) Re-engagement, if you've disengaged the PTO, moves from a second or two to about 7 seconds.
My guess is the above mentioned valve starts off clean, then gets clogged again. Going downhill for some reason makes it worse. Level ground some of the clog clears out.
I don't know. Grasping at straws. I don't have any interest in dropping the transaxle. Lot, lot of work. Dealer however will slam me if they do it.
Sidebar: I thought I'd price a trade-in just out of curiosity. Wow, you can't get a new one. He said Kubota is not building or delivering right now. I thought they are in the middle of a platform modification.
