I filled my rear differential fluid on my 2007 S60 AWD to were it seeped out of the fill plug. A few days later I had oil dripping from the bottom of the differential. When I investigated a little further I noticed it coming from the differential vent. Is this common after you fill the differential?

 

I don't have an AWD, so I can't say for sure, but it sounds like you may have overfilled it. I don't think fluid should come out of the fill plug, even when full.