Indeed. Though, is this not then an indication that my internal seals are intact and, well, sealing? 

On the air tightness front, there was a notable release of air on removing the breather, but as I say it wouldn't hold much pressure as the breather let go with me blowing through it.
I thought that was to support the half shafts when they are pushed in. I had to remove one of mine when it came loose after a cvj let go.As the axles have an oil retainer ring up near the seals, it's very hard to clean the axle tube out fully.
Agreed, the knuckles can be bought but have to be welded on..Hate to say it but that's one thing LR's have over LC's in that you can replace the swivel housings if they gat badly corroded.
My mistake, i will now beat myself with a birch branch...Neat being able to replace the knuckle ball but frankly not really necessary unless they are shot to bits. They are not a bearing part. They are just there for the wipers to work against. They aren't a contact part. Neat, clever, cool, but really ...
The metal ring inside the axle tube is an oil retaining ring to keep a puddle of oil against the seal. They're nothing to do with supporting the half shaft.
Can i have my birch branch back now?Well it's certainly somewhere you can rest the shaft as you slide it it so that you don't bugger up the new seal CG. Sure, but only really necessary on the long side of the diff. It can be a right pain getting the shaft located into the diff, I know and you can lever off the oil retainer ring if you you must. I have done rebuilds where the shaft has gone in, in a oner. But we did one at the last Lincomb where a dozen of us tying just couldn't get one to engage. It was bizarre. Handy having the retainer there so we could have a rest!
If only to bring about the aroma of birch leaves within the Jerman household…No. It's nice and I have still to beat the children with it.
Another advantage of the Range Rover and Land Rover axles is that the hubs are full of EP 90 so non of this contamination takes place.
Regarding the breather, I would have thought it should only allow excess pressure to escape, not excess vacuum. After all you wouldn't want a rapidly cooling axle casing as in a river crossing, to take a deep breath on entry and duck water in? I think the breather is working fine. Non return valve with a little retention of pressure is what it seems.
Makes perfect sense TP. This is how it is now. I didn't have any water present in the knuckles or axle casing so something must have been right. However this may go some way to explain why the grease from the knuckles got into the diff oil.he diff /axle casing should ideally be at atmospheric pressure at all times.The breather must allow air back in to alleviate a vacuum, otherwise oil will be sucked into the diff casing and water into the hubs past the wiper seals.