33 Ford rear has a click sound

[guy1unico]

I noticed there was not the proper amount of gear oil in banjo so i've been adding oil.
The driver's side rear clicks going forward and backward whether in or out of gear. It does not seam to hamper the drive ability but have not had this vehicle on a road trip yet.
Over the long weekend I plan to remove the tire and see if i can notice anything but I believe it is internal.
What do you think think this might be?