After reading RBT's recommendation along with input from others on this thread, it seems like there are not many offerings that are suited for out transaxles. I have zeroed in on one that looks like it is a correct match. It is a mineral oil and is API GL4. It is called:
VP Classic® Hi Performance SAE 80W-90 API GL4 Gear Oil
Here is a link to it:
https://vpracingfuels.com/prod...e-80w-90/?c=261&
Does this look like a good fit?