Rear differential failed at roughly 80,000 miles. Depending on failure, unexpected loss of traction or a locking up of the drivetrain could occur. We were lucky to catch it before then. Dealer confirmed issue with no clear cause. No warning lamps/messages/etc indicated that the part was failing. The only thing we noticed was increased highway noise, which could easily be ignored by someone who is not as aware of good/bad car noises.