I've no knowledge of 400's but since nobody's answered, here's my .02 cents
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On the 750 hub the smaller side of the spacer goes to the side of the hub with a flange for retaining the bearing (smaller dia. bore), the larger side goes to the straight thru bore.
Sealed bearings are that, sealed. So no grease comes out and no grease comes in, alas there's no sense in filling the hub with bearing grease.