@ls_rbls
I'm still trying to make this work, sadly...
I read though your info a couple times, and checked around on-line a bit before coming back as I really want to understand what I did wrong. I updated the field names so its make a little more sense.
I'm starting with these field fake fields to get the hang of things, because in the end there will be 20+ fields, with 50+ vehicles of information. So I want to make this work so I can use the actual information in the future.
So on my last attempt, The data came back as undefined. Can you assist please?

var vehicleData = {
"Vehicle 1": { WeightField: "3000 lbs", AxleField: "2", ColorField: "Red" },
"Vehicle 2": { WeightField: "4000 lbs", AxleField: "3", ColorField: "Blue" },
"Vehicle 3": { WeightField: "2500 lbs", AxleField: "1", ColorField: "Green" }
};
var selectedName = this.getField("VehicleDropdown").value;
if (vehicleData[selected]) {
this.getField("WeightField").value = vehicleData[selected].weight;
this.getField("AxleField").value = vehicleData[selected].axles;
this.getField("ColorField").value = vehicleData[selected].color;
} else {
this.getField("WeightField").value = "";
this.getField("AxleField").value = "";
this.getField("ColorField").value = "";
}
Use this as validate script of dropdown field:
var vehicleData = {
"Vehicle 1": { WeightField: "3000 lbs", AxleField: "2", ColorField: "Red" },
"Vehicle 2": { WeightField: "4000 lbs", AxleField: "3", ColorField: "Blue" },
"Vehicle 3": { WeightField: "2500 lbs", AxleField: "1", ColorField: "Green" }
};
var data = vehicleData[event.value] || { WeightField: "", AxleField: "", ColorField: "" };
this.getField("WeightField").value = data.WeightField;
this.getField("AxleField").value = data.AxleField;
this.getField("ColorField").value = data.ColorField;