MARLIN - I talked to my Allis collector Buddy. Allis calls their hyd/trans fluid 82? (three digit number, something like 824 or 825 Fluid. Not as catchy as Hy-Tran,
I think my Buddy's comment is very good too, "Whatever you use, I wouldn't mix one type with another, flush it and refill with only one type."
It's amazing what all finds it's way into engine or transmission oil. Part of the fuel mixture out R/C cars ran on was castor bean oil, and a few percent synthetic oils, 30% nitromethane, and the rest alcohol. I know the old Ford Traction-Loc friction modifier additive that actually worked contained some ingredient from whale's reproductive organs. Needless to say the newer version does not.