I also had a Pfaff 1475 and sewed on it for 25yrs. A couple years ago it started making a loud grinding noise when I sewed at higher speeds. Nothing else wrong with it, but when I started going fast this horrendous noise would shout out at me. Very unnerving. Felt like I was torturing my best friend!
My Pfaff dealer could find nothing wrong with it. Acted like I was nuts. I demonstrated the problem. They still couldn't find anything. Went from that shop directly to the local sew-and-vac shop and gave a demonstration and thorough explanation. They dug into it, changed out some belts and cleaned out some things and said it was fixed. Got it home, started sewing. Sounded great for about 30min, then the noise started again. At that point hubs took me shopping for a new machine, and my daughter got the old one. She only does small projects and mending, and never sews as fast as I do, so it should last her for many more years. (3yrs later and I still miss the old machine. The new Pfaff and I have never reached the same level of love.)