I have a new 300ci with less than 50k on it and it sometimes makes a high pitched noise that seems to be present only when the drum units are turning. The noise varies in pitch and loudness. I tried using the Sim codes to turn on the fans and motors, but the noise never showed up. Is there a part that has a known history of this noise? Any recomenndations before I start to take this thing apart?

I am not sure if this product has a similar fuser drive pack/unit with some clutches as
part of it but I had the same kind of noise
on a KM-C4035E and checked these clutches.
I ended up replacing the one causing the noise.
I was able to unplug one at a time and operate the drive and determine which one was faulty.
Hope this is of some help.
Regards
Ed

I have one of these that sounds like a bailing machine, When I run all the individual motors everything sounds fine, When I do a Developer refresh it sounds terrible, When I do the AC Calibration and choose just the Black it sounds terrible, also when I do any of the color units. Also noisy when warming up and when making copies. I noticed the Transfer belt had a tiny tear in it. Anyone run into this before.

had a 300ci doing same thing, the trans belt was walking over and buckleing. Replaced trans belt and noise whent away

Recently I found a squealing idler in the job separator. For the last three visits the customer complain of noises. Finally I got to hear it to. =^..^=