Diff & transfer box oils

[Clunk]

On a somewhat related note - when I change diff oil should I be using some sort of sealant on the sump and fill plugs when I screw them back in? Changed both diff oils a few months ago and didn't use any sort of sealant and I have noticed that they have been weeping a bit of oil. If I should have used a sealant I would also appreciate some advice on what to use?? Thanks, Gags.

I've never used any sealant on sump and diff plugs.... Shouldn't need to