Transfer Case & Diff oils... what's the best stuff?

[Lugnutt]

I've got a 72 K10 4x4 auto with a posi rear diff and about 95,000 miles. I've got the pre-interaxle transaxle transfer case; by which I mean it's all gears (see pic). and I've also got the posi rear end (see pics). I want to change out all the fluids with the very best oils I can including the front differential (sorry, no pic). Can any of you recommend the best oils for these parts? Also, based on the pictures, what is the proper description or name for these two components.

Thanks for the education, I'm humbled by the knowledge you guys possess.

[1969k10stepside]

The proper names...Well the transfer case is a New Process 205 (NP205) and the rear axle is a Corporate 12 bolt.The front unless it has been changed is a dana 44 open knuckle axle.As for the oils,I just put in regular ol' gear oil,nothin' fancy

[Big White GMC]

I've Been Using A Lot Of Lucas Oil Lately. Make Sure For The Rear And Front End You Use The GM Friction Modifier. Dealerships Should Have That Stuff.

[OLDCHEV4X4]

I use Valvoline 85w-90 gear oil. ( i think thats the weight) Only because thats the only kind the auto parts store gets in 5 gal pails. No problems yet.
You only need the "posi traction additive" if you have posi traction. Chances are that the front differential dosent have it.
Check the fill level on the TC to make sure its not over full. If it is, transmission fluid is leaking past the adapter seals and getting into the TC.