[KobaltBlau]

I did a bunch of research and decided that of the majors, Pennzoil non-synthetic was a nice gear oil, specifically the 80w-90 GL-5. I just yesterday saw some Mystic 80w-90 for 2.50/qt which is an even nicer dino based gear oil than the Pennzoil and very cheap. It is made by Citgo. The Mystic is marketed almost exclusively to the farm equipment/big rig market. There are a few other oils that fall into this category as well. I think your best options would be to find some Pennzoil or head to a farm or big rig supplier and see what you can find. You might have to buy a 5 gallon bucket but they aren't that expensive. You could post here what you find and I could give you some feedback. I can also provide more detail on why I thought pennzoil was a good choice as well.

People have reported success using Valvoline on this board, but I don't think it's a particularly good gear oil. Both 80w-90 and 85w-140 have been used by people with 915s (almost the same application really), but I wouldn't recommend 85w-140 weight in general unless you are in a hot climate and/or doing heavy DE or racing.

Here's an important question for you: What is the lowest temperature you drive the car in regularly?