Rockwell T221 Newbie

[67K10longbed]

I have been searching the internet/forums and I can't find the gear oil volume for the T221. Most say fill it until it runs out. I wanted to make sure I am filling it correctly. There are two large pipe plugs on the driver side. Is the top one where you fill it to? There is also a smaller pipe plug at the top of the case on the driver side? What is that for? I have read about using an elbow at the fill to allow it to be over filled. Is that just a 90 with a cap or are people extending that with a piece of pipe? I am asking because everyone mentions how the top bearing can starve for oil.