The upside is.. you wouldn't need a new transmission for just a differential or just the casing. These differentials do break with say too much power on a turn etc. Although you don't come across as the aggressive type of driver. I have literally had a friend or two limp a car to my house and we've changed both the differential and it's cover in under an hour to fix a broken diff/cover.
Friend bought this bonneville about an hour away from my place. He used a couple of gallons of fluid to get it to my place and then he repaired it with Barney's help.
Cracked cover
Bad differential
With some junkyard/scrap parts..it's rather easy to fix.
