How much gear oil

   / How much gear oil #11  
Agree, about half up on gear box or a tad less. Too full might cause it to start leaking from seals.

Gear oil does wear-out. Should be drain on bottom of box.

prs
 
   / How much gear oil #12  
There should be a set screw about half way up the side. Remove it and fill with oil until it runs out that hole. Then I would reinstall the screw and add a little more oil just for good measure,
 
 
Top