The servo making a clicking sound generally means the gears inside the servo are stripped. With the wheels off the ground see if the servo still makes the noise. If the sound only occurs when the steering is at full lock then that means the damage occurred because the servo is trying to turn more and it can't. Either way remove the servo and retest it, you can hold the saver still with your hand to put some load on it. If it still clicks in your hand then gears are stripped inside the servo. You can buy just the gears for many of the servos out there instead of replacing the entire servo. But first take it apart and check for damage to the case particularly where the shafts for the gears sit. If any of the case is damaged it's probably best to just get a new servo. What's the truck and what servo?