We had the horrible sulfurous smell. Seemed just like propane.
It was the left front axle sea or wheel seal. Gar oil was getting on the brakes and other places. Had it towed to Freighliner before bearings went dry.
Replaced seal and brakes and machined the drum.
It seemed strongest around the propane tank bay too.
Where we store it called and said we had a lot of oil under the front of the coach and down the wheel. He was checking for the leak too asyou don't want propane floating around in an enclosed storage with several millions of dollars worth of coaches. That would be one heck of an insurance loss.