Related Clues:

• They may be stripped
• First, second, reverse, etc.
• Adjusts
• They may be shifted or stripped
• See 16-Down
• They're sometimes stripped
• They work when engaged
• They're engaged!
• First, second and third
• First and second, for two
• Transmission innards
• Attunes
• See 8-Across
• They have teeth
• Drive and park