So I just bought a Ford 3400 backhoe and wanted to check all the fluids. When I went to check the rear axel fluid I unbolted what I thought was the fill plug according to the manual but I was wrong, the fill plug was covered in grease. when I took the bolt out I heard what sounded like a washer or nut fall inside. I attached a photo of the bolt I undid that's indicated with a red arrow the fill plug is the white arrow (this was after I realized I goofed and cleaned the fill plug off). What did I undo? Do I have to remove the 3 point cover to fix it or can I reach it through the access cover on the other side. I am new to tractors so please go easy on me lol. Thanks in advance!