So I just put seals in the axle of my Kubota B2910. Manual calls for GL-4 or GL-5. Supertech 80W90 is GL5 which should be a better high pressure lube than the factory UDT or synthetic UDT (GL-4). I expect it had the factory load of plain UDT. I am mainly going cheap to make sure I don't have any leaks. I may upgrade to synthetic once I am confident I don't have leaks. Most of these axles fail from being overloaded or severe corrosion. Any down sides to doing this. No signs of wear inside after 25yrs of use.