A portal axle (or portal gear lift) is an off-road vehicle suspension and drive technology where the axle tube or the half-shaft is offset from – usually above – the center of the wheel hub and where driving power is transferred to each wheel via a simple gearbox, built onto each hub.[1] It gives two advantages: ground clearance is increased, particularly beneath the low-slung differential housing of the main axles — and secondly, any hub reduction gearing allows the axle half shafts to drive the same power but at reduced torque (by using higher shaft speed). This reduces load on the axle crown wheel and differential.
The portal gear configuration is also sometimes called a drop gear or drop gearset configuration[2][3] (which, despite its similarity to the term dropped axle, produces the opposite effect).
- ^ "New Spicer portal axles for compact utility tractors - introduced by Off-Highway Systems Group of Dana Corp". Diesel Progress North American Edition.
- ^ U.S. patent 20,130,240,282
- ^ U.S. patent 6,095,005