Replacing your broken or worn out servo gears is very easy but you need to pay attention when opening your servo. Most servos have four main gears. These gears need to be put in the proper order for the servo to work correctly. Not only is the order important but also the mounting of the final gear (the one that is attached to the output shaft) onto the potentiometer. The “pot” has a flattened shaft that the final gear sits on. Make sure that this flat spot fits with the flat cutout in the final gear or your servo may not operate correctly.
Be sure to grease your replacement gears when you install them.