As your model contains a nested Vehicle
object your request must be in a certain format for the Model Binder to instantiate it in your controller action.
Your request url needs to be in the following format:
http://localhost/Home/GetClasBDetails?Type=1&Vehicle.Id=1&Vehicle.Name=aName
Take particular notice to the way the nested Vehicle
object is represented as the Property name separated by a period.
You need to make sure that the backbone request matches this, I have not tested this but I'm guessing that this should work:
data: {
Type: "Ford",
'Vehicle.Id' : 1
'Vehicle.Name' : 'ford mustang'
}