The old service info that I have, specifies 90W gear oil. Says the same on the old decal. No matter, whatever you use, I suspect you have too much oil in there, otherwise it wouldn't be leaking. Depending on which service procedure you choose to read, you either put some in there, then turn the hub so the hole is 'down', and let whatever drain until it stops. Or, after you have done the above once, then next time put 2 or 3 or 4 DROPS in there when you service it. In my case, maybe once every couple years, or maybe once every couple thous miles, whichever applies.
JMO (talking about 46-48-style fan hubs here)