Shimano Nexus 3 (SG-3C41) 2 and 3 gear problem - Ring Gear Unit Repair
After a bit of thinking I filed off cogs from the outside. So far so good, hub presents good enegagement at all gears. After few weeks it still runs good. Left is "fixed", right shown for comparison. I fixed (filed) both. Be careful to make them equal shape and that sharp border is not too thin and ortogonal to the side surface