Gear oil question

Eaton approves both conventional and synthetics from the major lubricant suppliers for use in their drivetrain components, so it would seem that it doesn't matter that much.

http://web.eaton.com/ecm/groups/public/@pub/@eaton/@roadranger/documents/content/pct_223059.pdf

I tend to be kind of obsessive about checking fluids, touching wheels and drivetrains when I stop for gas or rest areas. I once pre-empted a wheel bearing failure because I noticed one hub was a lot warmer than the other, for example. The only personal observation I can add is that my gear sticks (especially the transfer case, that was a huge reduction) and rear axle housing were "noticeably" (which I admit is a subjective determination) cooler to the touch after switching to synthetic in my old truck. I switched the new truck over to synthetic during my baselining right after buying it, so I don't have a frame of reference to know if it would be true in it, though.

 

I have been running Amsoil it's whole life in 5 speed trans, diff, transfer, and now at 500,000 miles
all original parts with no issues and supercharged.

 

It's perfectly fine, I ran Mobil LS in my 03 cases for 80k and I have It in my 15' cases now. Synthetic should just be avoided in the rear end if you have a mechanical LSD. 09' and up do not have those.