An older manual transmission driving technique used on non-synchronized gearboxes. The driver depresses the clutch to pull out of gear, releases it in neutral to spin up the input shaft, blips the throttle to match engine speed to road speed, and depresses the clutch again to enter the next gear.
You have to double-declutch if you want to downshift that old crash box without grinding the gears.
While unnecessary on passenger cars with synchronized gearboxes, heavy truck drivers still use a variation of this to navigate non-synchro multi-speed transmissions.
Also heard as
- double-clutch
Related terms
Clutch
The mechanical assembly that connects and disconnects the engine from the transmission.
Manual transmission
A gearbox requiring the driver to manually select gear ratios using a shift lever and a clutch.
Synchronizer
A friction mechanism in a manual transmission that matches gear speeds before engagement.
Heel-and-toe
A performance driving technique used to match engine speed while braking and downshifting.
Crash box
A sacrificial structural component designed to absorb impact energy during a collision.