They are roller/ball bearings. The oil is 90w-140 gear oil, levels are proper. The oil has been replaced a few times since I bought it because I had a bad cover gasket that would leak water into it, so I would change it frequently. (New gasket has since been put on)
Now that you mention it, It could very well be the differential. Since this is a "Culti-Vision" (offset engine) tractor the differential is actually under me on the "driverside"/left, which is where the noise comes from. Considering that the sound is constant no matter what gear I am in, and it varys depending on load, it makes sense that it could be the diff because its always moving/has load.
Thanks Frosty! Never even thought to consider that!
Transmissions hurt my brain, all those gears and bushings, shafts. I'll have to pop my cover and stare at it for an hour or something. I want to split the tractor and work on the transmission, but I don't know where to start! Then again, thats what I thought when I replaced the cylinder head, and I just tore into it without thinking too much, and she runs 10000x better now haha