1973 Dart Rear Gear Oil?

My Old Dart is 44 years "young" and new to me since November 21 of 2016. My question is should I add "change the oil in the rear gear" to my "list" of things I need to do for this cool old car? Thanks in advance!

Mike
It can't hurt 85w140 2to 3 quarts.get a new gasket as well