Big Bee Bush hog

[rustybutterknife]

Hey there,
working on getting this old bush hog going. It's a Big Bee LW-540. I have downloaded the manual and was just curious what type of oil the gear unit takes. In the manual it says SAE 90 or SAE 120 "Transmission oil". Seems I am not so well versed on the older terminology. I would assume that means gear oil. Don't think there's any soft metal in there (roller bearings, looking at the diagrams). If anyone has suggestions I'm open to hear them. tempted just to put whatever oil is in my hand at the time in there, but figured I oughta know what it's supposed to be.
Thanks,
-Josh

 

[Texasmark1]

I mow in N. Texas and usually in the warmer months. I like to use the heaviest gear oil in my equipment where a gear oil is recommended. On new
equipment I use synthetic 75W-140. Fill it once and forget it. Old stuff gets 85w-140 Dino oil. If it's a lower shaft leaker, I use Lubriplate 105 (any auto
parts store stocks it) in the soft white tube....made for engine rebuilding but works great in gearboxes as it's viscosity is between 140 gear oil and #2
grease. Stays in the box but thin enough to spread around and get in all the corners.

If your fill plug isn't vented, go to an auto parts store and get a ?" pipe vented plug. Will keep pressure off the gearbox and keep a worn lower shaft seal
from leaking....if due to pressure buildup in the gearbox.