How do you PREVENT the differential grease build-up?
 

I changed the oil in my diffs at about 25k or so. My JK is right around 30k now and both my front and rear diffs are smothered around their bottoms, even some areas down the axle tube, in grease vapor.

What do I have to do to get ride of this grease build-up, and prevent it from happening in the future?

Thanks!

You could have a leaking differential gasket or oil seal. Try Lube Locker gaskets to prevent gear oil leaks. If you overfill the differentials, the blow by will shoot out the breather tubes and make a mess of your axles.

Clean it all off with brake clean and see where the leak originates. Go from there.

Thanks guys. I will clean it with the break cleaner and see where these stains are originating. At the moment I am saving for Riddler diff covers and new diff gaskets to go with. In the meantime I'll find this leak.