Thanks for the help.
I did the changes but it did not succeed.
Reversing the inputs from pixhawk to the ESC, just reversed the problem.
In AUTO mode just one wheel moves, and in STEERING mode the wheels move in different speeds. The output voltage of Sabertooth is 3.8V in one side and 4.6V in the other.
Doo you think there are more parameters I can change to solve this issue?
Try another Sabertooth configuration?