@renbymon Likely yes. It's a shaft (hurr) with 2 disks on. It'll either be contacts or slits with an offset. So it measures time between seeing slits and works out how far/fast/which direction.
SOMETIMES Contact cleaner/other solvents can wash the crud out enough. But oftentimes it's just easier to replace.
The difficult part is matching the various parameters up o.< So you have to strip it to find the part number anyway >.<
@Jencen Thank you ^^