The parallax shader is not faulty, you are using it wrong. Why do you even try to make a tank with a shader and ~20 polygons? My advice: Scrap your idea and start all over again.
You can, f.i., take a quad (2 triangles) (for each wheel) and assign a wheel texture with alpha channel. Now you can animate the wheels easily by rotating them. The tracks should be a separate entity (to keep it simple) where you can now easily shift the U/V parameter.