Yes, this is a normal behaviour. The sound is created by backlash, when the motor is not able to provide enough torque.
Are there any chances to reduce the backlash? I already experimented with different PTFE tube lengths with no success.
What I am guessing: It seems that the Motor is a geared motor and the backlash or abrupt stopping creates some noise in the gearbox due to play of the gears. As someone already opened the motor to verify whether it is a geared motor?
No, the motor is not geared; the geared version was a previous-generation AMS, and it did not have any problems. This one is a stepper motor. I doubt there is any chance of reducing the noise by the end-user, as either the torque is not enough or the step is too wide. Sound-proofing seems the only solution to me.
I have a theory (from my limited knowledge of stepper motors!). Potentially a software issue, or mis-configured hardware. A stepper needs current at all times or else it will go slack…
So it could be that it feeds filament, the motor is told to stop, and to do so it switches off to save power, or it is not wired to recieve constant power. Hopefully someone can confirm my stepper knowledge (or lack of!).
I have just released the Viper 2 for AMS 2Pro, This should help to take a bit of load off. I have been using my Viper 1 kit on my P1S combo for well over a year with no wear to the infeed. I’ll let you know how the Viper 2 goes and if if helps the clicking once I do some more prints.
Visit @Beast-Lab to view the Viper kits
Nice try in trying to get downloads for your model… I do not see how this attachment can help, though.
It definitely took some strain off, the clicking is not as loud now. I’m glad managed to do something about it, Better than nothing.
I’ve just purchased an X2D combo and I’ve noticed the “clicking” from the rear motor within the first few prints.
I’m going from an A1 with a BMCU which was otherwise silent in comparison.
Very frustrating to hear that it’s a common issue and considered normal. Hopefully I can learn to ignore it as currently it’s extremely annoying.
I am currently going through troubleshooting with support. The issue is that they consider it normal as “they all do that”, but they are not saying it so literally. I think it’s a design flaw/fault, I can only urge everyone to log this issue with a support ticket.
Also something I didn’t know when I bought it, they won’t accept it as a return to investigate, it’s remote support only. It really is spoiling what is an excellent printer, as overnight prints with the AMS are not possible, you can hear it in the room next door. To add to the annoyance, people seem to report the original AMS used gearing and was quiet…
I created a ticket with support as I was also having feeding issues with the AMS 2 (getting stuck at the start of the print and during changeovers). I mentioned the clicking as well and sent a video through too.
They suggested trying to press the button on the rear of the internal hub when the filament was stuck to see if this was the issue and they also seemed to think the clicking could possibly be related.
They’ve offered to send me a replacement internal hub and a roll of filament as compensation. So it sounds like they’re possibly aware of the issue and the first thing to do is to replace the internal hub. I can see that this hasn’t resolved the “clicking” issue for a number of people in this post though so I’m not sure how successful it will be.
It definitely appears to be backlash from the filament buffer on the back of the printer. When it tightens and then suddenly releases it causes backlash in the tube and results in the gear slipping inside the internal hub in the AMS which causes the clicking
My AMS was also positioned on top of a shelf above the printer with the PTFE routing through a grommet in the shelf. I removed the shelf and sat the AMS on top of the printer which seemed to noticeably reduce the level of the noise. It’s still there (and loud) but not quite as audible as it was. So my best guess is it was probably echoing through the shelf and cabinet. I’m still not happy with it clicking so I’m hoping the hub replacement helps. If not I’ll try to pursue the issue further
I’ll report back when I can.
Bought a brand new X2D Combo just recently. It’s making the clicking noise from the start. I also got an H2C with 2 ams 2 pros, but they don’t make that noise when feeding filament. They are a lot quieter and just sound more “normal.” Just contacted support, so hopefully to hear back soon. 
Support just keep asking for videos. They also refuse to take the unit back for investigation, saying that they “don’t have offline support”. I feel a bit stuck and cheated by that, if they told me the sound was normal then I wouldn’t want the AMS 2 Pro. I am told the original is quiet, so would look for one of those. I am going to go back to support again.
My printer is 3 weeks old and makes that noise since one day before IT was silent, any solutions ? 
Just adding, I got the X2D Combo the other day and noticed the clicking straight away. I thought it was the toolhead knocking but realised it was the AMS2 when feeding. Very annoying I gotta say, can’t be in the same room (or even in the next one) without it being irritating. If it stays this bad I’ll have to start using my AMS1 as the main unit. Yet another thing to be dissapointed about with my X2D “upgrade”
Same here, it just appeared with my p2s and AMS2 pro (4 months and like 250 hours of printing time)
I am not sure if it is the buffer or the motor of the ams causing the issue.
Same here, brand new AMS2pro on H2D. It happens when the material feeds in an indexing fashion. I can’t understand why it doesn’t just feed continuously, at a lower speed.
I first noticed it after fitting a 0.8mm nozzle, during my first 0.8mm print (in vase mode). But it’s also the first time I’ve sat and tried to work while ignoring the printer. Yesterday it seemed super quiet printing a couple of small models with the 0.4mm nozzle
Same here. Received my H2C with two AMS 2 PRO and both do the clicking sound! Although both AMS are brand new and have the same clicking sound I would not consider that normal as it is way louder than the printer itself and it is not possible to sit right next to it during printing.
Did anyone have a solution or a workaround for that problem?
If I read it correctly, opening a ticket to the support is not really helpful as they just send a new hub motor with the same issue.
Mine is more of a clunk than a click now.
I have just got round to replacing the motor too, and also the problem remains.
Unfortunately it seems my AMS 2 has died. The click is worse than ever, and the rollers have begun to seize when it is pulling the filament off of the spool.