"Oily" sheen to metal near diff?

[icebiker]

Had my oil changed yesterday and my dealer did a pre-service undercarriage video inspection as part of their routine (tread depth, brake pad thickness, suspension, exhaust, rear diff). Every thing checked out fine. However when I relooked at the video I noticed an area next to the rear diff that had a sheen to it, kinda like it was greasy or oily. Attaching a picture and the video (see 1:56 -1:57) so you can see what I mean. Car is behaving fine, no noises, clunks, etc. I don't know what part that is and don't have a means to get under the car myself. Before I ask my dealer I was hoping one of you could weigh in on what this could be and if it's normal. Thanks

https://api.mykaarma.com/video-walka...mage_and_video

[jmciver]

Assuming the undercarriage of your car is relatively clean, which it looks like it is, the black paint on the diff does have a slight gloss to it. So everything is most likely fine. However, if you are concerned, back your car up on a pair or ramps (or put it up on a lift if you have access) and touch it with your finger to determine if there is any oily residue.

[icebiker]

Originally Posted by jmciver

Assuming the undercarriage of your car is relatively clean, which it looks like it is, the black paint on the diff does have a slight gloss to it. So everything is most likely fine. However, if you are concerned, back your car up on a pair or ramps (or put it up on a lift if you have access) and touch it with your finger to determine if there is any oily residue.

Thanks for this insight. If the diff's paint has some normal gloss to it then that's likely the reason for the sheen. The finned diff cover and surrounding bolts are clean and the tech actually states on the video that the diff is not leaking. I don't drive the car in the wet either. Thanks again.