2018 Wrangler JL (25,000 miles on vehicle all road & freeway). After driving into Rocky Mountains, 90 mile drive in good weather and snow, the traction control light comes on. This has happened at least 5 times, upon inspection the car smells of heat. Once the car cools and restarts the light goes out. Have taken to dealer multiple times and they say they can’t reproduce after driving locally. The rear differential fluid is jet black and gritty and the dealer (Larry H. Miller Jeep Havana St) says that is normal. NOPE, I told them! Any thoughts? I told them to keep the vehicle until they figure it out.