Double shifting, also known as double clutching, is a way to downshift a manual transmission to get more power from the engine at a lower gear. It is unnecessary in a car which has a synchronized transmission. The technique only needs to be used when driving a vehicle in which the engine and transmission are not synchronized, such as a truck or an older bus.
A vehicle with a manual transmission has several gears in which the vehicle runs. Higher gears make the vehicle run more efficiently at higher speeds because a higher gear has fewer revolutions per minute than a lower gear.
There are two contributing parts to a manual transmission. They are the engine and the transmission. In order for the gears of the engine to line up with the gears of the transmission both sets of gears must move at the same pace. The clutch facilitates the smooth transition between gears by disengaging the current set of rotating gears before the next set of gears engages.
Using the double clutch technique is necessary when driving a vehicle without a synchronized transmission, which ensures the engine and transmission gears are rotating at the same speed before a gear shift. All manual transmission cars are equipped with a synchronized transmission. This technique should only be needed when driving a truck or an older bus.
Instead of pressing the clutch, releasing the gas, and shifting directly into the next gear, double clutching uses a brief period in neutral to allow the gears to align properly. This is mostly used when downshifting, where the transmission is switching from higher gears to lower ones. Press the clutch and release the gas, then shift the vehicle into neutral. Release the clutch and pump the gas to increase the rotations in the engine, then release the gas and press the clutch to shift into the desired gear. Release the clutch and press on the gas to complete the shift.
