Ah, OK then.
Very old B'mann locos are sometimes termed "growlers".
The source of the noise is poor alignment throughout the drive train and/or cracked gears.
Some associate the sound to a coffee grinder.
You used the words "Very old".
So let's say, for the sake of argument, 15+ years old.
At that time B'mann locos were notorious for cracked gears.
This is the stigma, to this day, that haunts Bachmann N scale locos.
It appears to have been addressed.
I have Spectrum locos, both steam and diesel, that do not exhibit this problem. My Spectrum Dash 8-40C's were growlers, my Dash 8-40CW's were not.
All my Spectrum purchases are from 2004 or later.
FWIW I also own the new split frame Steam 0-6-0, 2-6-2, and 4-8-4 versions and they are all quiet and smooth. My earlier versions of these same locos (solid frame - pre '95) all suffered from cracked gears.
Check your gears.
Very old B'mann locos are sometimes termed "growlers".
The source of the noise is poor alignment throughout the drive train and/or cracked gears.
Some associate the sound to a coffee grinder.
You used the words "Very old".
So let's say, for the sake of argument, 15+ years old.
At that time B'mann locos were notorious for cracked gears.
This is the stigma, to this day, that haunts Bachmann N scale locos.
It appears to have been addressed.
I have Spectrum locos, both steam and diesel, that do not exhibit this problem. My Spectrum Dash 8-40C's were growlers, my Dash 8-40CW's were not.
All my Spectrum purchases are from 2004 or later.
FWIW I also own the new split frame Steam 0-6-0, 2-6-2, and 4-8-4 versions and they are all quiet and smooth. My earlier versions of these same locos (solid frame - pre '95) all suffered from cracked gears.
Check your gears.