I've since done some more work. It is definitely toast!
All the bearings have been out now (apart from the little B) and they are ever so easy to change if you get the heatgun on the case. I've also learned about shimming and what the marks mean. By moving the nose in-out and the backlash up-down, I can see that the pinion isn't leading in to the crown properly. It's too late (due to the wear) and hammering rather than meshing.
How it got that way I don't know. There are some gruesome worn diff pics on the web if you look hard and this isn't that. Either normal wear, impact and broken bits or rough surfaces due to lack of oil. I think the person who left it half in bits had maybe replaced pinion seal or something, got it wrong and then graunched it. Took pinion back out and realised what they had done. The little B doesn't look bad enough to me, but unless I can get it out without destroying it I won't know.
Anyhow, the marks I see in the blue after moving things around are not pretty! High and low dots and patches, no blue on the pinion tooth nose and not a smooth, even contact at all. They are just smacking/hammering each other and not guiding in. I'm not going to fit it as I know what it will be like! Unbearable
Anyone got a final drive they don't want in the UK?
