With a lot of talk lately on axles, I thought I'd take a look, and since I hadn't serviced them since I bought the truck, it was time, well past time. First fill plug, I got a little air (on second thought it might have been a little vacuum, so letting air in, not out) then oil poured out, which I wasn't ready for, expecting it to be right or low. I let about 1.5 qts come out, then decided that I wanted it the correct level, so carefully cracked the drain, and darker oil came out, ok, let's do the job right. Drained two, then realized it was almost 5:00 (Napa closing), so called and secured 2 buckets of their brand GL-5, $65 a 5 gallon pail. Filled the two back up, not before my bucket pump blew off one of the hoses and I squirted gear oil all over the shop! The last axle plug was too stripped for this to be an easy crack and fill, so decided to pass on that one, clean up, and get a new one ordered so I can do it right, once I can get it off. $15 for a new one. The fill hole did also reveal that it was overfilled to. 2 out of 3 too full.
2nd edit, realized that CM/R in the LO for the gear oil means only when maintenance or fouling occurs. Well, guess the truck is getting extra special care...and now I know the condition and age.. I wonder how old it really was?