AngularJs - Filtering out duplicates in select control

I have a select list of axleTypes, each having a Type property of either a Front Axle or a Rear Axle. I can not seem to filter out duplicate words of 'Front' and 'Rear'.

enter image description here

Update:

Html:

<select ng-model="axleType.Type" ng-options="type for type in uniqueTypes">  

Controller:

    $scope.axleTypes = API.GetAxleTypes();

    $scope.fixedAxleTypes = [
    { "$id": "1", "Description": "I beam, telescopic type shock absorbers", "Type": "Front", "Id": 1 },
    { "$id": "2", "Description": "Full-floating banjo housing", "Type": "Rear", "Id": 2 },
    { "$id": "3", "Description": "Something Else", "Type": "Rear", "Id": 2 },
    { "$id": "4", "Description": "I beam, telescopic type shock absorbers", "Type": "Front", "Id": 4 }
    ];

    // This Works
    $scope.uniqueTypes = _.uniq(_.pluck($scope.fixedAxleTypes, 'Type'));

    // This does not
    //$scope.uniqueTypes = _.uniq(_.pluck($scope.axleTypes, 'Type'));

    // This does not
    //$scope.uniqueTypes = _.uniq(_.pluck(API.GetAxleTypes(), 'Type'));

I am thoroughly confused. And yes, the API works, I copy pasted above data from Chrome > Network>Response window

Seeing the error that you added in your edit, I'm sure that the reason is what I described in my comment, which is the use of the (axleType.Type) expression for the filter in a context where that expression cannot be evaluated. Since you're not using the expression in the filter implementation, you could just omit it altogether, I believe.

What i guess is API.GetAxleTypes(); should be doing some asynch tasks like calling $http. if that is the case then $scope.axleTypes wont be of the array type you are looking for. The the GetAxleTypes can look something similar to this.

Service definition:

{
   uniqueaxleTypes:[],
   GetAxleTypes = function($http,..){
     var promise = $http({
       //config
     })
     promise.then(function(response){
       this.uniqueaxleTypes = _.uniq(_.pluck(response.data, 'Type'));
     })
   }
}

Then if you bind a scope variable to this uniqueaxleTypes it will always reflect the unique values.

Since $scope.fixedAxleTypes is a hard coded value, its working fine.