Truck and vans, one ton and HD3/4 tons with the Dana 60's also use the rearend oil as a lubricant, not grease. Whenever you turn a hard left or right the oil is sent to the bearings.
Most 1/2 trucks and cars use splash lube gear oil to the bearings. Those trucks are all built with full floating axles like the big boys. The older Fords with the 9" used sealed bearings with the bearings pressed on the axle.