Finally I've just replaced again the original parts, and reassembled it again. The coffee grinder, at least, seems to cover the noise with the music, but when you let it turn without playing, it grinds anything you'll want! Five hours of work for nothing.
When I bought it, the motor was a bit sluggish, bit it worked silently... I've had this same experience with several machines, and each time along the years I've said to myself: don't remove the old grease. It fills the wire down spots and teeth, and when you clean the gears diligently, unavoidably the great train becomes noisier...
Next time I buy a machine, I'll add some oil and nothing more!
I'm tired and discouraged!
Luck that the big motors 32 &34 never have any problem. Certainly they are much better than the old motors. I believe the helicoidal gearing it's much more silent than the straight gearing.
Brrrrr...
