Thank you guys for the quick response. As far as I know I modified the servos well. After doing it now I am able to get a full turn with my hand. The main thing is that I don´t know if the modified servos should still be connected to the same connector (Serv 1 o Serv 2) in the Adafruit shield and the fact that I don´t have any code to simulate simple wheels movement so I can see if they can do the job. If you have any code please let me know.