it all depends on how you are setting up the drop down. I would recommend not using viewbag/data for sending the information. Put it in your viewmodel build the list how you are building it but save it to the view model
viewModel.TrackList = TrackList;
then on your view
@Html.DropDownListFor(x => x.Track, Model.TrackList)
the for helper will override the selected property. In this case to set the selected value you would need to set viewModel.Track to the value you want selected and the for helper would then be set accordingly. Let me know if you have any questions.