Harmful to shift without clutch?

[Loren]

Rev matching is matching the speed of the engine to the speed of the transmission thereby making the synchros have to do less work. When you're clutchless shifting, especially downshifting, it's nearly impossible to do smoothly without doing some rev-matching.

Best example is the first gear downshift that a lot of people think is difficult. It's difficult if you try to do it from too high of a speed and too quickly, but if you slow down to an appropriate speed for first gear and give the synchros time to work, it will slip right in. OR, you can do it quickly and smoothly at a somewhat higher speed (still needs to be a mid-range first gear speed!) by adding a little blip of the throttle as you depress the clutch to zing the revs up, thereby increasing the transmission input shaft speed and allowing the gears to easily mesh.

Works even better if you learn to "double-clutch". That is, to let the clutch back out while you're in neutral so that when you rev the engine, you're REALLY spinning up the transmission input shaft. Then clutching again, slipping the stick into gear and declutching again.

It all takes practice. Lots of practice. Don't force it, just let things happen. When you have the input shaft speed right for the gear you're trying to go into, it will slip right in.

It's a Zen thing.