Well, I hate to disagree, but I just opened the rear diff to change out the oil, and the diff has grease in it. A good ammount, but IMO and from reading and suggestions from the LHS guru, not nearly enough. Anyway, I'm gonna put in 5K/7K/3K. Also the RTR has spider gear diffs if anyone wants to know.
hehe. ok humboldt was right on that one. I guess you can chalk the stock diff oil in the Lightning Pro as yet another advantage when you buy the Pro version.
You really should have upgraded the gears while you were at it. :\