The carrier bearings have races, the discoloration that can be seen in the housing is from that bearing overheating and burning the gear oil. When I cleaned off the discoloration there wasn't a lip at the edge of the discoloration, so I don't believe it had started to spin the race in the housing yet. It isn't obvious from the picture, but the carrier cap threads had started to deform and pull out of the housing slightly, so overall it's not a housing that I would want to reuse. I forget the exact price, but a new housing was under $250, all the stuff that goes in it adds up to over $1000, and it's not a quick job either.

 

There's a lot of dealers around here too that'll not hold up their end of a deal. Bad reviews and social can sometimes help, good luck.

I can tell you that I had recently rebuilt a front diff in a 2020 with 100k km ( 60k mi ) the complaint was no 4x4 and a noise. The no 4x4 was a outer vacuum hub not holding so we replaced with the dorman locked kit, 1 cv axle and a wheel bearing because the splines were all stripped. As for the noise the gear oil looked the same as what you posted, the spider gears were chewed up probably from trying to engage the 4x4 while moving/spinning (oilfield work truck) I got a complete bearing kit and a new carrier and installed. Even though the spider gears were in rough shape the bearings and races didn't look bad at all.

You may be ok to reinstall the cover and new fluid and monitor for abnormal noises... I also recall a lot of the older generations of f150s having a grey colored gear oil in the front diff from factory. I remember back around 04/05 seeing this for the first time and questioning it, I was told it was normal.

 

Wow…..that’s some crazy crap

 

The factory carrier bearing shims in my front differential had an extra 0.017" above and beyond what Ford calls for so the bearing preload was obnoxiously high and that would explain the carrier bearing failure I had. Overall I don't think that this type of failure is typical, but I have had horrible luck with my 2021 F150. The real telltale that something was very wrong was all the metallic paste that collected behind the pinion seal and axle seals causing them to leak; after finding that, I wasn't too surprised when I found where all that metal came from.

 

I don’t think it’s super common either.

I have the worst luck with cars sometimes and this is just one of them.

Hoping it all gets worked out when I take to the dealer to have them look at it.

 

I wonder if the case was machined improperly

 

Just and update………

Finally was able to get the truck into Ford.

They said the front differential will need to be rebuilt.

It will be covered under warranty and it should take a week.

I saved and brought the old fluid with me and they said that helped out a lot.

Now I have proof that there was something wrong before I bought the truck. I will be letting the dealer that sold it to me like this know.

I will be leaving them a negative review. Mostly for telling me they would help figure this out and then backing out of that help twice.

 

Last update.

it took two and a half weeks to get my truck back.

The noise is gone and this is what they did it.