I've done that to a trailer axle BUT that doesn't have fluid in it with vent holes or hydraulic brakes..
The Rear explorer axle would have the ABS hole at the bottom, vent hole on the axle at the bottom, from what I remember seeing this morning the brake backing plates can't be installed upside down so the brakes would be wrong too..
On top of all that I can't remember if the pinion will be able to get oil if it is upside down too.
~Mark