Double-clutching (technique)

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Double-clutching (also called double de-clutching outside of the United States) is a method of shifting gears used primarily for vehicles with an unsynchronized manual transmission, such as commercial trucks and specialty vehicles. While double clutching^[1] is not necessary in a vehicle that has a synchronized manual transmission, the technique can be advantageous for smoothly downshifting in order to accelerate and, when done correctly, it prevents wear on the synchronizers which normally equalize transmission input and output speeds to allow downshifting.

With this method, instead of pushing the clutch in once and shifting directly to another gear, the driver first engages the transmission in neutral before shifting to the next gear. The clutch is depressed and released with each change. A related downshifting or rpm-matching technique is heel-and-toe shifting, in which the throttle is blipped (i.e. momentarily opened during downshifting) by the driver's heel during braking.