Your chassis , has " full floating " rear axles. Meaning the wheel bearings are running in diff fluid, on races in a hub assembly, the axle has no contact with the bearings and drives the hub through, 8 bolts that hold the axle to the hub. There is a flange gasket between the axle and the hub, and if that's what is leaking it's an easy ; but slightly messy; fix.
Do you have stainless wheel covers , or alloy wheels?
If stainless covers , remove the covers and try to isolate the leak, may be obvious as soon as the covers are off, may require a clean up and drive the coach to pin point the leak.
If it is not the flange gasket leaking, and removal of the tires and hub is required, JMHO, that is not a DIY back yard job.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.