Rear diff/pinion seal leak

[SteelCity]

Bought a new to me 2022 F150 XLT end of May, Gold CPO. I already bought the Premium Care ESP through Granger. Love the truck so far and with the warranty not too concerned about things popping up. I knew when I bought it the dealer replaced the pinion seal and drained and resealed the rear diff. Two weeks later the rear diff was leaking, but the pinion seal looked dry still. Took it to another dealer closer to me, but under the same umbrella as the dealer I bought it from. They resealed the rear diff and looked good for a few days and I could tell they cleaned up the mating surfaces of the rear diff and cover way better than their other location as I could see bare metal.

The rear diff looks wet again but now it looks like it's the pinion seal that is leaking and splashing back on the rear diff.

Three questions:

1) Originally, would the dealer usually drain the rear diff to change the pinion seal and then reseal the rear diff and refill?

2) If the rear diff wasn't sealed properly the first time and leaked and now the dealer resealed the rear diff properly and it's tight, would that then push the fluid out the pinion seal if that seal also wasn't done properly the first time?

3) Could a clogged vent tube be building too much pressure and pushing fluid past the pinion seal?

Attached are pics now after they resealed the rear diff. The pinion seal area didn't look wet like this before.

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[FaaWrenchBndr]

Yes, a clogged vent could cause a leak

 

[SteelCity]

If the vent is clogged and pushing the fluid past the seal, would that seal now need replacing after the tube is unclogged? In the end I'll let the dealer fix it under warranty but like to know a few things before I walk in there.

 

[TJSparky]

Did you check the fluid level at the fill hole? Maybe it’s overfilled and leaking excess at the pinion seal.

 

[flasch192]

ford has had issues with pinion seals for awhile now .

 

[SteelCity]

An update... dealer replaced the pinion seal and re-sealed the rear diff again. Got it back and noticed it was a little louder than before, especially around 40 mph, slight vibrations while accelerating. Noticed the pinion seal leaking again this weekend, it's been two weeks since I got it back and wasn't leaking until now. I'm thinking the driveshaft is out of balance now after re-install, or maybe the bearing bad now and the vibration caused the seal to leak again? Have to stop by the dealer tomorrow for them to look at it again. All under warranty, but kind of a pain. I figured I would wait until my next oil change since it's on them to tell them about the vibration, but maybe should gone right back the next day, either way they would have to take it all apart again.

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