I see the tubes, seals, etc. you mentioned on page 80A of the manual. Appears there are two of the same seals on each tube and one higher up the tube with a different p.n.

Well, after a long hiatus I finally got the D6C put back together. I got to run it a little while cleaning a pond out, until the bottom of the pond gave up. Seems that a good bit of the jumping out of gear has been solved. But it still has a bit of an issue that I think is coming from the shifter itself. The keyway that holds it on the interlock shaft has a good bit of wear. I only got to put about an hour or so on it before I swapped to a d4h. With a little more use maybe I'll get it all ironed out. I had a short video of it working, but the file extension isn't accepted.