Reverse Gear Idler
This is used to select reverse gear. To do so, the first-reverse slider gear must engage the straight teeth; i.e., the ones not set at an angle. Because there is no reverse lock-out, reverse is often "touched" accidentally, and the teeth get chipped. As long as the chips are small, it's no big deal; virtually all these parts get chipped. The main concern is for a badly damaged gear, as a tooth might break off. I don't think these are worrisome, but I had a good used gear in my parts stash, so I replaced it. In this picture, you can also see the brown deposits that covered most of the inside of the case.