https://www.stengelbros.net/Suspension-Air-Valves-and-Controls_c_1746.html . Stuff on here. Lift valve for in the truck, and in the box down further. I remember in my highway days we ran lift axles on 48 foot flatbeds. Cab controlled for lifting when turning. I remember when you lifted the axle, it killed the service side of the brakes so you couldn't drag the tires, say if you were coming to an intersection, and slowing down. I got nailed on a toll bridge, I had raised my lift, but when I got to the toll, it was still spinning, so he charged me for it being down. Older fella told me to lift it, and once it was up, hit the switch down, then hit the brakes, the flip it up before it touches the road.