A back cover on any rear is just a lid you take off and replace the gasket. If the carrier is leaking at the banjo housing, a quick fix is to loosen it a little and wrap cotton string around the entire thing and then retighten. Back before we had RTV this was a standard fix and it lasted just as long as gaskets.
GL5 eats on gaskets. We now use synthetic 80W140 and RTV and have zero leaks.
