[MEDIK418]

Double clutching is used on certain types of transmissions that have no synchronizers. . .big trucks for instance. The rational is that when you pull the transmission out of gear, and hold the clutch in while you try to go to the next higher gear, all the other gears slow down to the point where it will not engage the next gear. If you let the clutch out as you go through neutral, it speeds all the gear shafts back up and makes it easier to go into gear. Fuller 9 speeds (and most other big trannies) rely on a 500 rpm drop to the next gear. I.E. if you peg the engine at 2200 rpm you can begin your shift. Without using the clutch at all when the engine drops past 1700 rpm, you can pull it into the next higher gear without so much as a clunk. Same goes for upshifting. . going up a hill, as your engine slows to 1700 rpm, you can slide it up into a lower gear by blipping the throttle to pull it out of gear, mash the pedal to the floor, and push it into the next lower gear and you'll never feel the thing go in. THe point is that if you don't use the clutch on these, you can hang the next gear as everything goes past the magical 500 rpm drop. If you don't use this method, you gotta double clutch. I am thinking that some of the older road racing trannies are like this. Anyway, unless you're driving a really old pickup or an 18 wheeler, you're wasting leg muscle double-clutching.