gear lube vs. tranny fluid

Then use Dextron-Mercon6. LOL

It's interesting how people WAY overthink things like oils.
Some are better than others, but when it comes down to it there are only three that matter.

Engine oil
Gear oil
French fry oil (which by the way would work just fine in out TF 727's and 904's)

I'm not that literal about it, but I know I use good quality oils for what is required mechanically and duty wise.