NHTSA Complaint #11501986 — 2021 FORD EXPEDITION

Front differential failed. I was driving to the mountains and when I reached snow level it was about 38 degrees F and I slowed to less than 20 mph and switched to 4A. Within a few moments I heard and felt a grinding sound from the front. I have used 4WD several times over the year or so I've had the vehicle and have never heard this noise before. I thought it was the hubs not engaging completely and so I switched it back to 2wd and while the noise was less it continued. I switched back to 4wd and I confirmed that 4wd was working but the noise persisted. I bought this vehicle specfically for its 4wd and my family's life depends on it working when we are up in the Sierras where it snows 2-3 inches per hour. When we returned I immediately took the vehicle to the dealer who informed me that it was the front differential that failed and parts are on back order. I am still waiting two weeks later. They said this is not common but why are parts on back order if it is not so common?