Originally Posted by Nichg
It's totally normal and I have seen it the same on every 11 and up mustang I have seen. Did the same thing on my 12 and 13 mustang, and that part in your video that is loose is the "breather" to make sure that the diff does not pressurize and to allow for fluid/heat expansion (like a relief valve in a sense). All vehicles and equipment have similar type "breathers". As long as you check you differential fluid level and it is to spec you are all set to go.
Kinda figured when I saw it, didn't know if it was normal to be that loose. Have 3.31 now, gonna get the 3.73 in the spring and I just wanna make sure everything is good before I get it done cuz of course once I get the new gears my diff won't be under factory warranty anymore