One time or another every racer has blown the gears out of their servos. In many cases racers just go out and buy a new servo to stick in their car or truck. Why waste all that money when it is so easy to replace the gears?

If you have an old servo lying around that needs to be fixed, just head on down to your local hobby shop and have them order a gear set for you and the next time you crunch the gears you'll have one ready to replace it with.
Here is what you need to do to replace those gears.
Each servo is a little different but you can follow the same general instructions given here. Just unscrew the 4 screws holding the case together. Some are located on top of the case, some on the bottom.
You may first want to apply a little tape to the bottom part of the servo to hold on the bottom of the case when you take it apart. If the bottom falls off while replacing the gears, it can be a real pain to get everything back into place properly.

Carefully remove the top of the servo taking note of how the gears meshed.
Note that the main gear also has a tab on it. This tab fits into a slot on the case and it is very important when reassembling that this tab fit into the slot on the case.
After you take note of how all the gears mesh, remove the gears from the servo and remove any bearings from the gears that you may have.

If possible try to replace the stock plastic gears with metal ones. Metal gears are not only stronger, but also give the servo more torque because of the gear design.

In most cases you will be replacing your gears with the exact same gears that it was originally equipped with. Most metal gears cost about twenty dollars and a whole new servo is anywhere from sixty to a hundred and thirty dollars, quite a savings. If you aren’t sure if there is a metal gear upgrade for your servo contact the manufacturer’s customer service department.

You will want to take what grease you can from the old gears and spread them on the new gears. You can also take a small dab of white lithium grease to add to it, but do not put on too much as it will only gum up the works.

Note the small tab on the main gear. You must make sure this tab is in the proper position so it engages the slot in that case. Different servo types may have this tab located in other places, but all servos have this tab in one form or another to limit the servo's travel. If the tab is not positioned in the correct place you servo will not work properly.