animated model export from blender to unity

i am making a game where i need a train to move on tracks path so i have used blender to give the path animation to move along the curve track path this is working but when i attach drivers to the wheels of the train to rotate the wheels along with the moving train,then when i export the fbx to unity assets folder the size of the fbx increases and blender and unity both become non responsive and then unity import crashes.is there any other way to export the fbx file to unity from blender.