This afternoon I finally got round to changing the front output shaft seal. I'll be honest, I've been putting this off. Not over keen on rolling about on a concrete floor.
It was basically a repeat of doing the front axle pinion seal with the same issues that I had there - old seal reluctant to come out, universal joint needle rollers happy to discharge themselves all over the place but I got there in the end.
First thing to do was to drain the old transmission fluid, and the book method is to remove the gauze strainer bolted on sideways on the side of the assembly - worryingly the bolts were barely finger tight but the good news was that the cork gasket was in good condition as I'd overlooked buying a new one. Gauze was clean as a whistle but I blew it out anyway with an air line.
Without working over a pit it was actually impossible to use the big special spanner to hold the yoke still while unscrewing it's big retaining nut as the spanner clashed with other bits of JCB - probably OK if the gear box was on the bench but not in situ.
However my Milwaukee M18 1/2" impact driver unscrewed it reasonably happily so it wasn't a problem .
So job all done time to change the filter which according to the hand written date on it was last changed in 2002.

In a bit of an awkward position but amazingly I was able to unscrew it by hand. New filter duly marked up with today's date and screwed home having oiled its rubber sealing ring.
According to the book this transmission takes 14 litres - so I put in 12 and dipped it. Bally thing was over filled. I ran the engine briefly to fill the filter but no still too full

So crawling back under again (repeatedly!) I loosened the strainer and must have drained off at least another litre before the dip stick was happy. As over filling was I think partially the cause of the seal failing it was important to get it right.
A big clear up of tools and a floor sweep and horror of horrors I found an oil seal reinforcing tubular spring of the sort that biases the seal lips onto the shaft - sinking feeling - would need a total repeat operation to refit the spring

However all was well - inspecting the seal that I had removed it's spring was missing - phew

So time to try it - a quick trip round the field in both two and four wheel drive - all seems to work - (but of course this yoke / prop shaft is rotated by the front axle in two wheel drive any way)
Left standing a couple of hours while I had a shower and supper (a nice gammon rasher

) and so far no more pools of oils.
. . . so hopefully that's another job jobbed
Sorry no picture - I was too oily !