It is very surprising that a PIttman motor would make noise. I have them in a bunch of locos and I have never had the motor be the problem, it has always been something else in the mechanism.
That said, could the screeching sound be a lack of lubricant on the motor bearings? Would it be worth putting a drop of very fine oil on the shaft at each - perhaps Wahl hair clipper oil, or Labelle oil? Maybe the factory worker screwed up and assembled the motor with no lubricant. While some PIttmans have ball bearings, there are still many around that just have "oilite" bearings, sort of a porous bronze that I guess holds lubricant. Some may be just plain bronze.
Would it be possible to disconnect the motor and see if the mech still makes noise?
