Whether a car gets its juice from a battery or from nitro, we all depend on at least one servo to make it do what we want. But servos are prone to mechanical failure and will eventually need maintenance. The most common problem is usually a worn-out or stripped gear set. You’ll know that the gears are stripped if the servo doesn’t turn or if you hear a crackling sound when you give it radio input. This step-by-step shows you how to change a gear set with minimal frustration.

YOU'LL NEED > Jeweler’s screwdriver or Torx driver, depending on the     servo > Replacement gear set > Silicone grease > Cotton swabs, small brush > Motor spray, bearing oil (optional)

ONE

First, remove the servo horn or servo-saver that’s attached to the output shaft (assuming that the servo has already been removed from the vehicle). Thoroughly clean the outside of the case with a brush, and be sure to remove all dirt from the area where the shaft exits the servo case.

Thoroughly clean off the case surrounding the output shaft. You don’t want dirt or debris to drop into the gears when you disassemble the servo.

TWO

Remove the four screws that secure the case. If your servo uses Torx screws, get the correct Torx driver; don’t hack at the screws with a Phillips tool.

Use the proper-size screwdriver to remove the screws from the servo case; you don’t want them to strip out!

THREE
Carefully separate the top part of the case from the bottom. Press down on the servo-output shaft while you pull up on the case tabs to allow the gear set to remain intact. Note the tiny shafts on which the gears spin. If there is a rubber seal, care- fully remove it and set it aside.

Left: To split the servo case, apply light pressure to the output shaft with your thumb...

Right:...while you pull up on the case tabs.

FOUR
Carefully separate the top part of the case from the bottom. Press down on the servo-output shaft while you pull up on the case tabs to allow the gear set to remain intact. Note the tiny shafts on which the gears spin. If there is a rubber seal, carefully remove it and set it aside.

Above Left: Hmmm...there’s absolutely no way you’ll ever get these gears back on there
the right way...

Above Right:...unless you lay them out in the order you took them off. Then it will be easy.

FIVE
Use cotton swabs to clean out the grease from inside the top case and around the shafts where the gears spin. If any of the gears have chipped teeth, small pieces of plastic may be hidden in that goop, so it’s best to clean it all out.

Right: Thoroughly clean the inside of the servo case; look for signs of debris and broken gear teeth.

Left: Inspect all the gears, and look for chipped teeth and stripped sections.

SIX
If your servo has one or more ball bearings for the output gear (the top one with the output shaft), clean those bearings with motor spray and then apply a tiny drop of bearing oil to each. Exposure to motor spray can weaken some servo cases, so it’s a good idea to carefully push out the bearing with a screwdriver to avoid getting motor spray on the case.

Left: Clean all bearings and apply a drop of oil to keep them running smoothly.

SEVEN
Use a light bearing oil to lube the near gears. This is especially important on servos with metal gears. You can be generous with the oil, but don’t use so much that it will seep out of the case when you put it back together. Also put a drop of oil on each shaft.

Right: Apply a bit of light lubricant to the gear teeth.

EIGHT & NINE
Install the new gear set. Usually, the gear with the output shaft (the top gear) has a notch in it to limit its travel within the top of the case. Look inside the case to check the range, and place the output gear in the center of the range.

Left: Reassemble the servo with the replacement gears, and pay attention to the proper gear arrangement.

Right: Reassemble the servo with the replacement gears, and pay attention to the proper gear arrangement.

TEN
If your servo has a rubber seal, wipe it clean, place it in the seam between the case parts, and then reinstall the screws. That’s it!

Right: Reinstall the screws, but don’t overtighten them. Again, small screw heads can be stripped easily, so don’t overdo it!