I've got a 2018 Nissan Patrol that I use for everything from the school run to weekend desert trips, and it's been a solid car overall. But recently, I've noticed a whining noise coming from underneath, especially when I'm coasting or decelerating, and it's getting louder by the week. It's accompanied by a slight hesitation when I shift from 2WD to 4WD, which is starting to make me a bit anxious. I took it to a local garage in Dubai, and they just said the fluid looked a bit dark and suggested a flush, but I'm not convinced that's the whole story.