What type of manual transmission lets the driver pre-select the next gear before changing?

A preselector gearbox lets the driver pre-select the next gear before the actual change occurs. The transmission generally remains in the current gear until the driver operates a separate pedal or control to engage the selected ratio.

This arrangement was a clever way to make unsynchronized manual transmissions easier to operate. Instead of coordinating a conventional gear lever and clutch pedal at precisely the right moment, the driver chose the next ratio in advance and then triggered the shift when appropriate. Many preselector designs used planetary or epicyclic gearsets and brake bands rather than the sliding gears found in older manual boxes.

Preselector gearboxes were especially prominent before automatic transmissions became widespread. The Wilson design, developed by Walter Gordon Wilson and produced by Self-Changing Gears, appeared in vehicles from the late 1920s onward. Armstrong Siddeley cars, Daimler buses, racing cars, and military vehicles all used variants.

They were sometimes marketed as “self-changing,” but that phrase can mislead: the driver still selected the gear and often actuated the change. A torque converter is a coupling device, not a gearbox, while an overdrive unit and transfer case perform different transmission-related jobs.