Ah I must have missed that. Then yeah check your fluids, and if so replace the bearings. I'm not sure tho, have yet to open up a differential other than to look at it and change fluids lol. Sorry I can't be of more help, maybe someone else has some more input.
P.S. Now that I think about it, my front diff made a lot of noise. I checked the fluid level and realized there was none -_-... filled it up and it seemed to fix it.