I noticed the top side of the differential case has a thin layer of oil residue. The surface was moist. It was not soaked and there was no obvious drips forming. I wiped it clean, so far after maybe 3k miles and did not notice any new oil stains.
Is it possible that it overflowed and came out of a breather? (Is there a breather?)
The car has 35K miles and never had any differential work done.
I've heard other people had similar problem. Is it a leak? Is it a problem?
How long does manufacture warranty covers the differential?