This is a front live axle with
kingpin inclination with angle atan(1/4)=14.036... degrees
diff lock
portal axles with 8/24 gear reduction
constant velocity joints
Ackermann steering
The following picture shows the very high ground clearance and highlighted kingpin axis (in red):
A .ldr file can be found on bricksafe. This .ldr file includes building steps.
There are 2 black steering links on top and 2 grey links at the bottom. These create a 4-bar linkage. A caster angle can be obtained by angling the whole axle by setting up the 4-bar linkage properly.