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” is a flattened shaft that the final gear sits on. This flat spot is easily visible on standard size or larger servos. Make sure that this flat spot fits with the flat cutout in the final gear or your servo may not operate correctly.
Note: Nylon geared servos will accept metal gears of their equivalent. Example: HS-81 nylon geared servo will accept HS-81 metal gears. Also Be sure to grease your replacement gears when you install them.