318is Gearbox Oil Seal / Diff Pinion Oil Seal

[joker]

Hi

I'm changing the two rear gearbox oil seals and the diff pinion seal this weekend. Got a couple of questions:

Have heard that "self-locking nuts" connecting propshaft to flanges either end need to be renewed, ie cannot be reused, is this the case?

Car has covered 150k, how likely that the gearbox output flange so worn that changing seal will result in worse leak than currently, have heard this can happen. Current leak not too bad, very slow but going to France in 10 days so want to cover all bases.

Thanks