I'm not very technically inclined and I'm sure it is a silly question, but I changed the gear oil out in my axles (Dana 30, Chrysler 8.25) with Valvoline synthetic blend 80W90 gear oil. I have about 3 quarts left over. Can I use this same stuff in my NP242 transfer case? I noticed while I was under there that I had a drip coming from the TC drain plug and it was brown. If, not what should I use? Also, do I just fill it to the fill plug or lower?