While towing, the vehicle shifted suddenly, then smelled like burned oil when moving the vehicle. It would still drive, but seemed to take extra effort to move, and was louder than it should be. The fix was to replace an axle seal and gears in the rear differential. This took several months to obtain the correct parts, and was stuck at the dealership while they were waiting. Luckily it was covered by the extended warranty, but was without the truck in the meantime.