After the corrosion problems with the differential I ended up buying a second hand one. 63 euros delivered. Turned out to be a pretty good deal. I pulled it to bits to check the condition and it looks like only the pinion bearings need to be replaced. Happy days!
It isn't a series 2a differential, however, it is a series 3. Nearly the same - not quite - anyone know all the differences? (answers on a post card etc)
Instead of wire locking on the axial bearing caps running through the clamps for the axial adjusting "wheels" there's just a split pin
I wanted to replace the pinion seal at the very least and I hoped the pinion bearings would be good
Not shown in the pictures but the pinion bearings show signs of over heating
Axial bearings in acceptable condition - so they will stay
De-rusting the casing
Also after angle grinder and wire brush attachment
Rustyco gel treatment for a few hours =>
Pulling large bearing off the pinion
Re-position your puller when you get more space!
De-rusting done - only small areas with light rust in those hard to reach areas. Treated with Brunox - and now over (under) coated with Ferpox