There’s two mechanisms in the truck part: one for the steering and one for the stabiliser leg extension.
The truck has eight wheels, and all wheels are steered (with the back wheel turning counter to the front wheels) to enable a smaller turning circle. A nice touch is that the wheels on the very front and very back axles turn to a sharper angle. This mirrors real world four wheel steerer trucks and is to deal with the fact that those axles have to track a larger turning radius. The image to the right from Sariel shows the effect.
The lock-to-lock travel is quite small (it’s at full lock in the image above) so the curb to curb distance is going to be very large in relation to a real vehicle.
The stabiliser leg’s are highly geared (three rotations to full extension) and at one point the drive is transferred by two 32072 Technic Knob Wheels with the result that the operation is a bit jerky. There appears to be a bit of room in the truck bed where that transfer takes place so that’s a possible future improvement.