ORIGINAL: Dads like rc too
The diffs usually come dry meaning a small wipe of thin grease on the inner planetary and out ring gear is all you get. Since the Tornado diffs are not sealed, you don't want to get carried away on the ring gear lubrication. A small amount of lithium grease will keep things lubed. Even with this you'll notice some grease blending from the diff cups but just wipe it off when your going over your buggy. As far as the inner gears go, for general playing around you can fill them up with the same lithium or of you want them to lock up a little more you can add 10.000 weight fluid. Some people like to mix and match their diff fluids like heavier in the rear so the diff is locked up more and lighter in the front for better cornering and climbing. I think for running around the yard just making sure you have some grease in them will be fine just to keep them from wearing.