I bought a maintenance manual for my truck and have been learning how to do standard maintenance on my own. I'm confused about something though. It says to service my transfer case lube (GL-5 SAE 75W-90 gear oil), differential lube (GL-5 SAE 90W gear oil), and manual transmission lubricant (Gl-5 75W-90). Are all these fluids the same thing? I know what the differentials are, but are the manual transmission and the transfer case the same thing? Because I know there are two diffs, one in the front and one in the back. And between them on the drive shaft is the transfer case right? Am I missing something?