Drive fluids

It has been years since I checked the fluids in my old pickup truck as I only drive it a thousand miles a year or less. I need to add some fluids to the transfer case and both front and rear differentials. Can I use the same 80/90 weight gear lube in all three? Do I fill it until it runs out of the fill hole? How about the transmission? That is low also. What do I use and how much? Fill it to the top until it runs out the fill hole? It is a four speed manual transmission. Thanks for your help.