So I'm cleaning up the "new" 2 speed rear axle for my dump truck and figured I'd change the gear lube and I also noticed the eaton high/low 12v selector has a oil reservoir for itself. What gear lube should I put in the diff? the selector says sae10 on it but is there a specific lube for these things?

Also what is the actual way to drain the diff lube to refill? Since I have axle off truck I'm gonna just spin the axle to where the fill plug is down and drain it like that for now but later on down the road when I want to change it again and its mounted to truck. do I just take the lower bolt out of front and it drains like that or do I have to pull the whole gear plate off front of diff and reseal it everytime fluid gets changed? And if that's the case most rear ends like this probably have the original gear lube in them cuz that would be a pain to do every 50k miles or when ever you changed it.

Thanks mike