Donna,
Thanks for the confirmation. I'm not really into the new machines. I like the old ones so the only "newer" machines I have any experience with are few. We've got the mid 70s 413s, 538 and 518, the mid 90s 4622A, and the 2001 vintage 3810. That is the extent of my plastic gear machines. I know the 4622 has the same basic design as the 518 / 538 for the feed dog drive, all three have straight cut plastic gears.
Glad to know that Singer is doing something different. I hope the spiral gears hold up better.
Joe