1x SCL82-17 - F9033310 - Selector Barrel OVERDRIVE
This part is only for use with the OVERDRIVE gear ratio set. It is not interchangeable with the DIRECT set.
Overdrive gear ratios:
14x29/14x31
15x24
20x26
21x23
20x19
28x24/29x24
Part no. 23 in Manual page 11 (Exploded view page 4)
 
Part as photo