I just replaced the hydraulic tandem pump on my M4700 with an ebay Chinese(we ll see how long it lasts). It wasn t an exact fit but made it fit eventually. The pump head box where the pinion that turns the pump is located had oil in it when I took off the old one. Do I have to refill it and how do I do that? Not sure about the correct nomenclature so I included a picture. Much obliged.