Drive gearboxes creating almost a shrill sound


So we have one Neo hooked up to our Toughbox mini on the KOP drivebase with Omni wheel upgrade. When we run the Neo over USB C it makes a very loud sound. Almost like really loud whistle (hence shrill). Is this because we haven’t worn in the gears yet? We legit like lathered the gearbox with grease so just wondering why.


I know for greasing (atleast on other products), they recommend running gears for 30 minutes, before you grease them. I believe the idea is to be more aggressive and allow the burrs to fall off before getting stuck in the grease.


Could be some of the wires aren’t plugged in correctly or the brushless drivers are set up wrong


Can you post a video showing this? If possible, put the robot on blocks so the wheels don’t touch the ground. Try to capture the sound coming from the gearboxes then any sound coming from the motors. Do this with different power levels.


Yeah I will once tomorrow because thats when I have access to robot.


I forgot to ask if you have contaced the manufacturer, Rev Robotics, about this. I have never had the need to call them but all my correspondence with the other FRC focused manufacturers/suppliers have been very helpful.


Here are the videos:
The sound scales with the speed as well.


All the links are “unavailable.”


Now try?


The constant whine that is speed dependent and the “once per revolution” pulsation sounds like what we were getting when we had the “drivetrain that veers” problem. I think what fixed it for @che.smith was swapping out one complete gearbox + 2 motors. I think the motors had been replaced already. The gearboxes were disassembled and checked several times. I am suspecting that the plastic gearbox housing might have been deformed, say pulled from the mold too soon.

Do you have a second gearbox you can install?


Yeah I can change everything except the output shaft. Would that work?


We always “run the gearboxes in” as part of the assembly process. Assemble them dry, and run (ideally at varying speed) for 20-30 minutes. We just run them at one speed. Disassemble, clean out all the metal debris, apply grease to all gears, and reassemble. This makes a huge difference in how quiet and smooth the gearbox runs. You will get a surprising amount of metal debris from some gearboxes when you do this process.

The other test is to put a 1/2" wrench on the output shaft and spin the gearbox. You can easily detect tight/loose spots. This is an indication of an issue with how the gears are meshing. A good gearbox should spin smoothly without any detectable differences in the amount of force… This is also an easy way to get a before & after running in sense of gearbox health. We have seen both issues with poorly made gears and with warped housing.


Maybe the videos don’t fully convey the sound, but I wouldn’t be terribly concerned about the sounds I heard in the video. Double check to ensure everything is assembled properly and there’s no issues with gear bevels being pointed in the wrong direction or bolt head rubbing against a gear. Then run the gearboxes again to see if the noise level has changed (or changes as the gears wear).

On another note, I noticed you only have one NEO per gearbox. While the NEO is the shiny new motor that seemingly outperforms the CIM motor, I’d still suggest following the traditional wisdom of having at least 4 total motors in your drivetrain (2 per side). Having more motors not only offers more torque (and thus acceleration), but also helps manage the load experienced by each motor. The less load each motor experiences, the happier it will be. This means less heat build-up, less current draw, and reduced odds of tripping the circuit breaker for each motor. Unless your robot is particularly light, I highly suggest running 2 motors per side.


Hi there,

This gearbox doesn’t sound quite right. There’s some troubleshooting steps that I would go through:

  1. Ensure that the round bosses on the gears are facing the bearings. The flat sides of the two cluster gears should be up against each other, and the flat on the output gear should be against the E-Clip on the 1/2" Hex Output Shaft.

  2. Ensure the four #10-32 screws securing the ToughBox Mini housing to the AM14U4 Inside Plate are not over-tightened.

  3. Ensure the R6ZZ bearings are fully seated in the ToughBox Mini housing.

  4. Ensure that the NEO Motor mounting screws are not overtightened

  5. Check to make sure that the two bronze washers were installed between pinion gears and the Motor Housing.

  6. You can slightly adjust the gear spacing on the NEO motors to the first cluster gear. You may resolve the binding by slightly loosening the NEO motors, spinning the gearbox by hand and then re-tightening the motors.

  7. This sounds counter-intuitive, but there is such a thing as too much grease. I’d remove most of the grease from the gear teeth interfaces and reassemble. It looks like there is some grease oozing out of the FR6 bearing in one of your videos, potentially indicating too much grease applied.

Please check the above items and respond with your findings. If none of the above steps resolve your issues, we can look into some replacement parts for you.



I have taken a listen to the noises. I think that there are likely a few different things going on. The NEO does have a harmonic noise to it, but not something that would cause the screeching you are seeing.

Following @Nick_Lawrence 's advice above would be a good place to start.


You may have a tough time re-assembling the gearbox without the output shaft.

Find a substitute axle that is 1/2" dia. or slightly smaller. When you remove the gearbox from the inner plate, use the substitute axle to push the output shaft so it comes out along with the gearbox. The substitute axle will hold your center pulley assembly in place on the outer plate. When you are ready to re-install the gearbox, use the output shaft to push the substitute axle out.


Thanks all. I’ll try out your ideas and update you.


Ok so I removed the gearboxes cleaned them and ran one with neo one with a miniCim. They weren’t connected to any pulley or anything, just mounted to KOP side plate (as if they were mounted on actual drivetrain). Note the output shaft was not supported on other end but we ran them without grease as all and both the mini cim and neo sounded similar and reasonable. Im going to mount them properly tomorrow and test but just an update.