The axle is lubricated by means of the transmissionmounted
lubricant pump which gets oil from the
axle suction port and supplies it to the hub section
pressure parts to lubricate and cool hub drive
and multi-disc brakes.
Oil returns to the sump through the drive shaft bearings
and axle housing. Brakes get their pressure from the brake valve, in the case where the brakes would have leakage you'd fill the front axle with transmission fluid, braking power should be poor since leakage occurs, pedal pressure would be noticable lower.