Shifting Gears

If your current car gets good fuel economy but it’s no longer fun, or even very easy to drive, maybe it’s less the car’s fault than your own limited driving skills. After all, most of the energy that a motorized vehicle uses in its lifetime is wrapped up in its manufacturing, from mining and refining the metal ores to drilling and refining the oil used for lubricants and plastic parts to cutting, bending, pressing, welding, and assembling all of those parts. Why waste all of that embedded energy by pooping out on an otherwise serviceable vehicle?

For instance, a common complaint we hear from those with manual transmissions is their inability to easily downshift when trying to climb a hill. They press the clutch pedal and grit their teeth as the transmission grinds noisily into the lower gear, shaking their right hands to remove the sting of the vibration. They wonder how much longer that gearbox will last and how they can hide the embarrassment of sounding like they don’t know the rudiments of driving a “stick”.

Luckily, “there’s an app for that”! It’s something every big rig driver knows quite well, more out of necessity than skill. It’s called “double clutching”. The procedure is mandatory if you want to drive big trucks since the gears in truck transmissions (and many race cars) are built for maximum strength, necessitating squarely-cut, unsynchronized gears. The gears in most car transmissions are more helical in shape and have rotating synchronizing gears that help you shift. Think of them as “automatic manuals”. When those synchronizers wear out you’re left with a grinding gearbox, unless you know how to drive like a trucker!

So here’s the procedure:

  • Press the clutch pedal down and shift the transmission into neutral
  • Let the clutch pedal out and briefly tap the throttle pedal – up to 3000 rpm or so is good enough (depends on the transmission)
  • Quickly (and quietly for a change!) press the clutch pedal down and shift the transmission into the lower gear
  • Let the clutch pedal out and press the throttle pedal to accelerate, as usual

You’ve pressed the clutch pedal twice instead of once – that’s why it’s called “double clutching”. But the secret to its success depends entirely upon that brief goosing of the gas pedal with the clutch pedal out. What you’re trying to do is match the speed of the transmission’s output shaft (driven by the drive wheels, turning at a rate based on your car’s speed and the gear you select) to the speed of the transmission’s input shaft (connected to the clutch, which is connected via that clutch pedal to the engine). By letting the clutch out and revving the engine you spin the input shaft and its gears up to a speed that better matches a lower gear ratio (larger gear, physically) on the output shaft at your current speed. In other words, you do what a synchronizer does when it is still working.

Of course you could just grind those gears, put up with getting your hand buzzed, sound like you’re an idiot, and wear out the gears to the point where the transmission starts slipping out of gear. Then you’ll need a transmission rebuild or replacement, either of which costs some serious money. And cars without a working transmission really don’t have good trade-in value! Wouldn’t you rather learn something new and impress your friends?

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