Dave most of the drop axles here in Washington State steer and use two shocks to dampen any wobble they may get while down and running and centering springs mainly to keep the wheels from flopping one way or the other while lifted. While down they run centered by excessive caster the draw back is you must lift the axle before backing. Some new drop axles will change the caster setting via an air valve controlled by the back up light circuit so you can back up without lifting the axle and others will automatically lift the axle when the truck is put in reverse.
I once got an overweight ticket for lifting the 2 drop axles on the truck and 1 on the trailer of the loaded truck and trailer I was driving to back in the job off the State highway, totally unreasonable State trooper the sh!t head knew that I had to lift the axles to back in and as soon as they came up he was there with his scales the ticket got thrown out but it still wasted my time having to go to court
