I have been looking for this specific vehicle and found one Utah with 89k miles. On the drive back to CO I noticed on multiple occasions an extremely loud sound coming from area of the tranny. It reminded me of downshifting at high speed where the motor revs high and brakes the vehicle. Only thing is- the RPM’s don’t go up when this sound hits. And it did it high speed cruising, at low speeds while slowing to stop, and a few times in between, does not matter gear. The only service light on is the service tire monitor light which is other issue and I don’t have question on right now. No engine light or tranny light on. Has 6.0L V8, I thought at one point it sounded like a jet lowering gear to land lol. Never heard this before in any vehicle I’ve owned, thoughts?
Diagnosing a sound is hard enough to do when you can hear it let alone when you can not. But I would guess it is a gear/bearing noise. Here is an article i wrote on how to go about diagnosing a noise.