A simple-minded response from me. On the couple of occasions that I had to work on the pto on my WD last summer, I always ended up questioning if I had the pto shifter rod inserted the right way into the shifter lever. I always wanted to have it point out so the I could get the cotter pin in easily. But, the manual shows that it goes the other way; and I think that it is correct for the proper shifter rod clearance.
I also had a situation where the pto was a little too hard to engage for my liking. This was after replacing some pto bearings & gears due to brush hog abuse. If your tractor has ever had any gears replaced, the service manual cautions: "If clearance between idler gear and intermediate gear is less than .004" backlash, use two gaskets (between pto housing & torque tube)". I now have a thicker gasket installed & the pto engages easier, but I don't know how to measure the backlash.