Look man, I have done a lot of things over the years and didn't ever figure I'd have to recollect in exquisite, accurate, detail the finer elements of those things. I'm a big picture guy and not a pick-addict.
Having had a 10 and a 20 over several years, along with at least a dozen other tractors, and that (the JD 4000 association) having terminated back in '07, and the fact that they look and work pretty much (TO ME) the same, other than the 10 being a diesel, sometimes I get confused.
Usually I put in caveats that identify the origin of my comments and whether or not they can be taken at face value: As I remember, I think, I was told, mine did bla bla, it seems to me, this or that manual says, the guy at the dealer told me, this how I attacked the problem, etc.
On the seal, I THINK the 20 is the one that had the 1000 rpm PTO adapter stowed beside and to the left of the PTO. As I said, I don't remember if the 10 did or not and as I said I didn't remember if I replaced seals on both. When I said I'm probably stepping out of bounds on this I was referring to the fact that I never had nor worked on a 3000 series and presumed that they may be similar to the 4000 but it was just a guess.
I DO however, remember that the one I changed was a surprise in that I didn't have to drain the whole shebang to do it and picking the Oring out and installing the new one was an easy task. I DON'T remember how I found out that I didn't have to do the drain before I made the repair.
So sir, CUT ME SOME SLACK! Everybody on here didn't spend 25 or 45 or whatever number of years as a JD dealer associate of whatever sort you were, in a specific ag related business.