Finished up a rear differential/viscous coupling/CV axle repair on a '17 Hyundai Santa Fe. 104k miles, customer was in town visiting from Omaha (I'm in the Twin Cities) when it let go. I didn't get much back story, only that the customer heard a loud bang, followed by a burning smell, followed by a rotational noise any time the vehicle was in motion.
As soon as I opened the door, I could smell burnt gear oil. Upon inspection, I found the rear differential case quite literally cracked in half. Not just part of it, the entire housing was split in two. Hyundai didn't want the core, so I tore down the failed unit expecting to find bits of the spider gears everywhere. Not so....
The ring gear and side gears all looked perfect. It was the pinion gear that self-destructed. I saw no evidence which would indicate a prior leak or lack of maintenance, I can only assume that the owner got caught on a slippery surface and as the rear wheels were flying they suddenly found a dry patch to bite into sending a shockwave of torque bind back through the drivetrain.
Another possible contributing factor: the thing was wearing badly worn Kumho tires on arrival. Extreme inner shoulder wear on the rears (I'm talking cords on the inner 1/3, 6/32nds on the outer 1/3rd). I found no glaring issues with the suspension during my inspection, and an alignment needed to be performed following the differential repair regardless. In case anyone is curious, these are the rear end angles I was presented with:
L/R camber: -2.1/-1.0
L/R toe: -1.2/-0.7
I got everything as close as I could: ended at -1.1/-0.7 camber, +0.5/+0.5 toe.
TLDR: 2017 Santa Fe, 100k, $5,500 for 4 new 19" tires, rear differential, viscous coupling, CV shafts, and 4 wheel alignment.