80 w oil vs udt in tranny

[kstruckfarmer]

Have a 1984 b5100 with loader. manual says either udt or 80 weight gear oil
Any opinions on best choice. Will not be using in extreme cold. Have very slight leak at axle. Would the heavier oil be ok for hydraulics or bad for pump?

 

[85Hokie]

Have a 1984 b5100 with loader. manual says either udt or 80 weight gear oil
Any opinions on best choice. Will not be using in extreme cold. Have very slight leak at axle. Would the heavier oil be ok for hydraulics or bad for pump?

If not used in cold - the 80w will be a good choice. People often complain that the less viscous UDT will leak through worn seals, and that could be an issue in your case, however the heavier 80w will need to work harder to leak due to it's initial thicker viscosity. If you get the temps up on the 80w, it will flow easier and thus leak equally as well.

The oil leak - can that be fixed easily or not worth the effort at this point in time?