I have used 90w gear lube in the past with few issues.
I resealed the box and reassembled the box.
On this current project I just add a grease/STP/gear lube mix that just flows like cake batter at 70*.
This mix is slick as snot on your hands and is just barely pourable into the top fill port. Certainly good enough especially considering what was in there for the last 50 years.
