Manual transmissions — Two-stage gearshift movement In a synchromesh manual gearbox, the gear shift lever requires two distinct motions to change gears. What does the first movement accomplish before the lever is pushed or pulled to engage a specific gear?

Introduction / Context:
A modern synchromesh manual transmission uses a shift lever that first chooses a shift gate (selector rail) and then engages the desired ratio. Understanding the two-stage motion clarifies why mis-shifts are rare and how detents and interlocks prevent two gears from engaging at once.

Given Data / Assumptions:

• Conventional synchromesh gearbox with selector rails and hubs.
• Driver moves a single shift lever through an H-pattern gate.
• No electronic or automated actuation is considered.

Concept / Approach:
The lever motion has two components: a lateral (cross-gate) selection and a longitudinal actuation. The lateral movement chooses which selector rail and synchronizer assembly (hub sleeve) will be actuated. The longitudinal movement then slides that chosen hub sleeve to engage dog teeth after speed equalization by the synchronizer rings.

Step-by-Step Solution:
Move lever sideways → choose the correct selector rail/synchronizer set.Pull/push lever fore-aft → move the chosen hub sleeve toward the target gear.Synchronizer friction rings equalize shaft and gear speed.Dog teeth engage, locking the gear to the shaft and completing the shift.

Verification / Alternative check:
Workshop manuals describe the “selector” step first, followed by “engagement.” Cross-gate springs and detents confirm selection before engagement.

Why Other Options Are Wrong:
Moves the synchronizer: movement happens after selection, not as the first action.Meshes the gears: dogs engage only after selection and speed match.Operates the clutch: the clutch is pedal-operated, not by lever selection.Locks the selector fork: forks are guided by the selected rail; locking is not the primary “first movement.”

Common Pitfalls:
Confusing selection (cross-gate) with engagement (fore-aft motion).

Final Answer:
selects the synchronizer