Newbe with a couple of questions. Puchased a Craftsman 19.5 hp 42" deck with auto trans. No manual was provided. 1997 model. Today one of the axels migrated out of the differential housing about 7 or 8 inches. Some fluid was lost when I removed the axel for inspection. I reinstalled the axel and heard a click when the axel bottomed out. now it seems to be back where it belongs. I would like to top off the fluid, what type do I add to the transaxel? Hydraulic fluid? 20/50 motor oil? Will I need to bleed the system to remove any air pockets? This is done by leaving the mower in gear and pushing it backwards without the engine running? Any help would be apreciated.