I'm guessing that's your flange. Yeah, that should be tight. If it's what I'm thinkin of, you should have four bolts that fix it to the axle flange or the tcase flange. I can't think of any other "big metal rings" in that area.
2000 Ford Ranger XLT: SAS, Sliders, Bumpers, Gears, Lockers, Shafts, 33gal gas tank, Shortened from 130 to 112" WB, Home brew bed and spare carriers,
Receiving: tons and a 351w stroked to a 427.
1972 Ford F250 "Explorer", 390fe Big block, lime green
Receving: 14bolt rear w/ disks, cam, 650cfm 4 barrel, intake, exhaust,