Allis 50/50 4X4

I'm looking to find out what type of trans oil I need to use in my 50/50. My manual says to use Allis Power Lube 15/40 and that's all it says about the oil and I'm pretty sure this isn't available anymore. I changed the oil because of water contamination and I used Shell Rotella 15/40 T-4 and the boys over at Bob the oil Guy forum says that I shouldn't use motor oil so I called my local Allis dealer and they told me their using Hy Trans fluid but she didn't know what weight it was. Does anyone here have an opinion on this? Thanks.

Mark