Thanks. that does look like my gearbox.
I didn't have it far enough apart to mess with shift fork, but the shaft between linkage and shift fork on right side has an extreme amount of play.(up/down and in/out) Enough to allow one rain storm to fill up gearbox with water then freeze, pushing input shaft seal out. (Lucky it didn't crack case) But everything functioned properly after that.
No clunks or noises first time I put in pto after working on it.
Don't believe I got the large and small worm gears (71 and 74) mixed up. Assembled large gear to right side as per illustration (unless it's a mirror image) Not sure improper assembly is even possible? That said I didn't get at rear worm gears and I have one direction on each winch drum=Hmmmm. Will check bad shift fork shaft operation, then going to pull front cover back off and have one more look. While apart I will tie off controls and move input shaft by hand to see what's going on.
If you look at diagram it's not that complex changing two large bearings going into front cover and the two input shaft bearings, but has outsmarted me so far... haha.