Hi all,
So, I just went past 101,000 miles on my 2021 F-150. It was time to change the oil, and I crawled all around checking everything I could see and touch. I noticed what appears to be a leak on the sides of my rear differential...on the driveshaft side, right near where the axle shaft connect. It's almost like a weep hole? Here are a couple photos. Is this a leak? Is there a seal on the inside? Why would it leak? What should I do?

 

Check your vent hose and make sure it isn't plugged. Remove the hose from the axle tube and blow through it and make sure it flows. Then check that the fitting that goes into the diff isn't plugged the recommended way is remove the fitting and check it off the diff so if something is plugging it doesn't go into the diff. If you don't want to remove the fitting you can use a small piece of wire or brake clean straw and see if its clear. If the diff vent is plugged it can pressurize and leaks can form, the axle tube is welded where the round button is there and if the missed a spot it might be sweating from that. Once you check the vent you can brake clean the oil sweat off and monitor it also make sure the diff isn't overfilled.

 

My rear pinion seal was replaced under warranty at 45,000 because it was leaking...

Here is a related youtube video (don't know if this site lets members post links):