I also doubt he is part wolf if he appears to be mostly Shepherd. Many people will say their dog is part wolf for the bragging rights, which makes it very difficult for actual wolfdogs because their behavior is quite different from that of a dog. If you are interested in finding out if he has content, there is a test through UC Davis. Even wolfdog people, who breed mutts, look down on those who breed wolf dogs without knowing the parents and lines because wolf dogs are naturally more wild and it is even more important to know where they come from when breeding.
Skadi, AKA Lady Wolfington, GSD 4.6.12
Grim, AKA Bones , GSD 7.7.13