<VV> Axle shafts

[Hugo Miller]

I posted here yesterday about having play in my right side axle shaft 
flange/yoke where it comes out of the diff. No responses yet, so I had a 
peek at the book. There is of course a big castellated nut thingy behind 
the yoke which in theory I might try & tighten. But I gather that 
actually retains the differential bearings. so a) if there is any play 
in those bearings, something pretty nasty must have happened to cause 
it, and b) if there is any slack on one side, you should be able to feel 
it on the other side also, as the whole diff carrier will rock.
I haven't been underneath to try tightening that castellated nut yet, 
as I suppose I should do if only to eliminate it, but assuming that it's 
NOT that, what other possible causes might there be? Play in the 
differential gears in the diff carrier? Play in the output yoke splines 
into the differential gear? It seems unlikely that there would be wear 
in either of these places, since there is not a lot of movement there in 
the parts relative to one another. On the other hand, there is no noise 
coming from the diff, and no oil leaking out of it.
Anybody had any experience of wear and/or play in these locations?