In the old days we would remove the filler plug and stick the hole grease gun in it and fill it up. A fill up would probably be good for another 50K miles. If you start pressuring the box you are risking pushing the grease out the bottom seal. IMO.
Oh no, I'm not gonna put that much in it. I wondered about just sticking the end of the grease gun it there. I'll try that first, since it's so easy to get to. Thanks.