Browse over 9,000 car reviews

What is double clutching and how do you do it?

Until synchromesh arrived in the transmissions of mass market cars and trucks, double clutching was the way to keep that transmission together. (image: Unervi Gonzalez - Unsplash)

Q: What is double clutching?

A: It's a technique that was once necessary in order to drive vehicles smoothly and without damaging them. These days, however, it's pretty much a lost art, known only to those who continue to drive vintage vehicles for whatever reason.

First, let's get a couple of things straight: we're talking here about the art of double clutching meaning a very specialised driving technique.

Also called the double clutch technique, this has nothing to do with modern, dual clutch, or double clutch, transmissions. These new-tech gearboxes use two sets of clutch packs to allow a manual transmission car to be driven like an automatic. This is, with just two pedals.

The technique of double clutching has nothing to do with that, although its history does concern manual transmission design. But a standard transmission from a long time ago.

Specifically, we're talking about transmissions that didn't feature what's called synchromesh in their design. The synchromesh hardware allows gears inside the gearbox, rotating at different speeds, to be sped up and slowed down so that the teeth of each gear will mesh with its neighbour when the driver moves the gearstick.

Without this speed adjustment, it's very likely you'll have a clash in the gears' teeth at which point there will be a terrible grinding noise and possible gearbox damage.

So synchromesh solved this problem and, at the same time, removed the requirement for the driver to double clutch. Knowing how to double clutch was once part of life rather than an exotic technique. But what exactly does the technique involve?

It works like this: When the driver is ready to shift gears in a vehicle with no synchromesh (also known as a non-synchro gearbox) the first step is to press the clutch in.

Then, instead of moving the gearstick from one gear to another, the driver pulls the gearstick into the neutral position.

They then let the clutch back out. This gets the gears inside spinning faster and – hopefully – allows the teeth of the two gears involved in the shift to line up and engage cleanly and without crunching.

The next step is to press the clutch in again, and then select the next gear before allowing the clutch to engage again. And you're done.

If you get it right, there'll be a silent, clean change of gears. Get it wrong and there'll be those horrible graunching noises and you might find yourself stuck between gears with the vehicle effectively in neutral and going nowhere.

Old timers also know that double clutching is not as critical on upshifts through the gearbox, but is absolutely essential on downshifts in non-synchro transmissions.

They also know that to make downshifts even less likely to crunch, the driver should give the throttle a small stab when the car is half-way through the gear change (that is, with the gearbox in neutral and the clutch out) which helps bring the gears into harmony.

It's quite a complex operation which also happens in a very short second or two. Hand and foot co-ordination is the key as well as the muscle memory to make each movement in the right sequence.

Of course, carmakers are always chasing a better experience for their customers, and that's why the synchromesh gearbox became the default setting, allowing driver to just slip between gears with a quick, single dip of the clutch pedal.

Old timers call this granny shifting, but it's how those of us who still drive manuals know the world.

The term double clutching has actually made it to the gaming world and some versions of Grand Theft Auto (GTA 5) feature a double clutch function that gives the car a burst of extra speed.

Take it as read that this was never the aim of real-world double clutching and bears no resemblance to the real thing. Being a GTA 5 double clutch expert won't save you from the gearbox of a 1920s car or truck.