Issue with center diff brain on Nero possibly (squealing noise)

[Reborn8]

I have a question in regards to the brain diffs. This past weekend my son and I had a few big tumbles with the Fazon and Nero. Nothing from the norm but it seems the center brain diff might be messed up.

I noticed on my sons Nero that when I have it in the default position (all diffs unlocked) it makes a loud squealing noise from the center diff and if I turn the knob to the next setting (center diff locked) I hear no real change. I can hear a change when I switch to center and rear diff locked and all diff locks. The noise was so bad I ended up unplugging the center brain diff plug in. Now the noise is gone.


If I move to all open or center diffs locked I hear nothing now. I do her servos move when I switch to center and rear diff and all diffs locked.

I have a feeling something is wrong with the center diff but I wanted to find out the best way to troubleshoot.

If the center diff brain controller is not working will it be in an open or closed state? I am new with troubleshooting this so I am trying to go about this in a methodical way to figure out what is going on. Any help or advice is greatly appreciated.Thanks in advance.



Thanks.

R8 – Team Sinister

 

[lonee]

Sounds like an broken diff lock.
I fear that you have to unmount the diff and maintain that. The noise could come from damage pins which are locking the diff.
Also tha noise with the inplugged servo. It will make noise when the servo tries to move the pins into the holes, but it can´t because of the damaged pins.

lonee

 

[Stitch]

I had a similar problem with the rear and mid diff. I opened them but they looked fine. I wrote the support and they send me new diff brain servos including the rings with the pins

I replaced them and the problem is gone and did not come back. There is a small design change in the ring which seems to help.

 

[Reborn8]

I had a similar problem with the rear and mid diff. I opened them but they looked fine. I wrote the support and they send me new diff brain servos including the rings with the pins

I replaced them and the problem is gone and did not come back. There is a small design change in the ring which seems to help.

Thanks for the advice Stitch. I need to open the center diff up and check it out.

Sounds like an broken diff lock.
I fear that you have to unmount the diff and maintain that. The noise could come from damage pins which are locking the diff.
Also tha noise with the inplugged servo. It will make noise when the servo tries to move the pins into the holes, but it can´t because of the damaged pins.

lonee

Thanks lonee,

I will open the diff up and check it out.

 

[chevyrumble]

It sounds like your center diff servo has gone bad. I had the same thing happen to my Big Rock. Like Stitch did, I emailed Arrma and told them that it had gone bad and they replaced it under warranty, which was nice. If you want to troubleshoot the diff servo's and brain without taking the whole truck apart you can open up the Radio box and try unplugging each diff servo one at a time or even change the order they are plugged in. But if you are hearing extra noise that is definitely one or more of the servo's. I can't find the thread, but I am pretty sure another person had posted a video of their rear diff servo that had failed, you can hear the servo in the video is clearly not working correctly. I found the video on YouTube and put a link to it below, but I cannot find the Forum thread now. I hope you enjoying wrenching on your RCs as much as running them. Pulling the center diff and replacing the servo is a pretty big job.

www.youtube.com/watch?v=K1voeEQo3is&t=33s

 

[Hye]

Mine did this on second battery pack. I was babying it too. Thought it was because lipo was low. Heard the noise and it sounded like something was in the fan. After 5 min inspection I changed the settings of diff lock and the noise changed. Now that I'm seeing others have the same issue I'm worried about my arrma Nero investment. It's to soon to have problems. I watched some YouTube on it and replacing the servo. Sucks to think I have to do all that after 2 packs on my first day. I bought it through amazon prime. Sending it back. Sad

 

[Stitch]

Actually it is not a big deal. Write the support to replace the small servos.

For me this solved the problem for good i.e. >50 packs and no problem.

 

[stefangun]

My BigRock had the same issue with the rear diff servo. I could repair it for ~10 battery packs by tightening the screw at the servo outdrive (this fastened the little ring which acts like a servo saver). Now all three diff servos are gone bad. The one I maintained as well as the front and center ones which I never took out of the diffs. I never changed the diff settings during load or at movement, always made the car stop before changing the setting.

I am very disappointed by the BigRock build quality. Also had 4 screws that I was unable to loosen using hex driver (and I'm using quite good tools - Arrowmax tungsten spring steel). Had to use brute force to get them out - one was holding the motor pinion on the axle.

I'll give Arrma support a try. But I don't believe they will replace all three mini-servos at once. Will keep you updated.

Defective Nero BigRock Diffbrain Servo

• stefangun
• Mar 20, 2017
• 1

This is how it sounded out of the box. It had three issues: The holding pin of the tiny middle...

Nero BigRock diffbrain servo after repair

• stefangun
• Mar 20, 2017

Sounds good!

 

[mrfurious40k]

To avoid having this issue in the future do the following before installing the diff brain servos whether new or after being removed for diff service: Before installing the servos in the diff housings, connect your receiver and diff brain to all 3 servos and power the system on. Cycle through all the modes and then switch it back to all diffs unlocked. This will center the servos before you install them so they don't have overtravel in one direction or the other that causes the buzzing noise and premature failure. The tech at ARRMA told me to do this when I called for my replacement servo and I haven't had a problem since with buzzing servos or failures.

If they are just noisy but still working, they might not replace them but if they stop switching the diffs, ARRMA will take care of the issue under warranty.