Wikipedia:Portal:Portal/Selected article/6

Portal axles (or portal gear) are an offroad technology where the axle tube is above the center of the wheel hub. Compared to normal layout, this enables the vehicle to gain a higher ground clearance, as both the axle tube and differential casing are tucked up higher under the vehicle.

Due to the gear reduction at the wheel which lessens the torque on all the other drivetrain components, the size of the differential casing can be reduced to gain even more ground clearance. Additionally, all drivetrain elements, in particular the transfer gearbox and driveshafts can be built lighter. This can be of use in reducing the centre of gravity for a given ground clearance.

As it requires a heavier and more complex hub assembly, however, these systems can result in an increased unsprung weight and require robust axle control elements to give predictable handling. In addition, at higher speeds the hub assembly can overheat.