But the original design for CR-01 has used a servo saver (manual page 8 refers), and 樓主 want to add another servo to modify the CR-01 to becomes 4-wheel steering, so he is asking where can he buy an additional servo saver.
But you are correct that most crawler may not be used servo saver as the steering power may not be good enough to sheer the Big Big and heavy wheel. That means CR-01 is not really a ..........crawler