Thanks Hunt so we're really no further forward other than returning it to Bachmann ?

I have a HO scale Bachmann Baldwin Shark A and B unit. The B unit makes a grinding noise when running. I have had both units matched CV  wise on a friend's DCC layout and have lubricated the unit but to no avail. Other than fitting a NCE decoder is there anything else that I can do to suppress the noise from the B unit.