Leaking Clutch Master Cylinder: The Art of Rev Matching

This morning, Silvana had a surprise for us.
She opened her doors, as she usually does, she started her engine, as one would expect her to, but when time came to engage the first gear, she started crying as if she was in terrible pain.

Her clutch was fully and permanently engaged.
First I thought she was being moody, perhaps she wanted a day off, but eventually I understood that it was a gift. She was offering me the opportunity to make a tutorial on clutchless driving.

Welcome to this special episode, courtesy of Silvana, where we will cover a survival technique that every manual transmission driver might find useful one day: The art of rev matching.

When the engine is running, and the clutch is engaged, the input shaft of the gearbox is spinning. As long it is spinning, trying to change gears will grind them… or worse, destroy the gearbox.
So how do we do it safely? The answer lies in matching the rotational speed of the gear you want to engage in with the speed of the output shaft, which transmits the power to the wheels.

When these speeds match precisely – not close, but perfectly – the gearbox allows the gear to slide in without resistance.
This is called "rev-matching", and it allows us to shift without depressing the clutch. On early cars this was a basic skill, required from all drivers.
Imagine trying to match the teeth of two spinning gears. If they rotate at different speeds, they will grind. When their speed is perfectly synchronized, they mesh smoothly, without effort.

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