Had 100k maintainence done 2 weeks ago. This included changing the diff fluid. It's still wet looking near the bottom of the cover so I called the mechanic and asked if that was normal. He said it may take a while for it to dry as its very oily fluid. They try to remove what they can w a paper towel if there's any excess on the cover. This sound legit or do I have a seal leaking? Thanks.