Precept pinion seal failure
Just had our coach in at Ford dealer for State inspection and asked them to check into grease I noticed on the exterior of our rims. Turns out the pinion seal was leaking quite a bit and throwing gear oil everywhere underneath. Coach is a 2019 with only 4k miles. Not sure I would have caught it if the grease didn't show on rims because when not in use it is parked on gravel and wouldn't have seen a puddle.