From reading some recent posts, it seems like there is some disagreement or ignorance as far as the exact and proper way to downshift using the double clutch method. I'll try to keep this simple as I describe a normal 4th to 3rd gear downshift:
1. Driving along in 4th
2. Depress clutch pedal
3. Shift into 3rd
4. Release clutch pedal
Usually the engineers match the gear ratios well enough that this should all happen smoothly, but it can't be perfect all the time. The synchros do a lot of work in order to get the drive gear and 3rd gear spinning at the same time, and the wear on the synchros is what will cause that grinding sound over time. Now, if you want to preserve the life of your transmission, and look (and sound) cool doing it: follow these simple double clutch instructions. Remember, it's called double clutching because you use the clutch twice.
1. Driving along in 4th
2. Depress clutch pedal
3. Shift into neutral
4. Release clutch pedal
5. Blip throttle
6. Depress clutch pedal
7. Shift into 3rd
8. Release clutch pedal
If you did it right, the shifter will slide effortlessly into place with no clicking or grinding sounds. If you followed the directions, but still met some resistance getting into 3rd gear, then you are blipping the throttle too much or too little.
When you blip the throttle with the car in neutral it causes the engine and transmission to move at the same speed. If you blipped it just enough, this speed will be the same as the axles, too, and everything will come together.
An important thing to realize is that the car is not in neutral if the clutch is in. The shifter must be in the middle of the transmission, and the clutch must be released for the car to be in neutral.
If someone has told you that double clutching is revving the engine while the clutch is in, they are wrong. That only does half of the work and does not get the transmission up to speed.
Here's a "diagram":
ENGINE-TRANSMISSION-AXLES/WHEELS
The transmission is right between the engine and the axles/wheels, so if you don't get the transmission moving, too, you're not double clutching.
1. Driving along in 4th
2. Depress clutch pedal
3. Shift into 3rd
4. Release clutch pedal
Usually the engineers match the gear ratios well enough that this should all happen smoothly, but it can't be perfect all the time. The synchros do a lot of work in order to get the drive gear and 3rd gear spinning at the same time, and the wear on the synchros is what will cause that grinding sound over time. Now, if you want to preserve the life of your transmission, and look (and sound) cool doing it: follow these simple double clutch instructions. Remember, it's called double clutching because you use the clutch twice.
1. Driving along in 4th
2. Depress clutch pedal
3. Shift into neutral
4. Release clutch pedal
5. Blip throttle
6. Depress clutch pedal
7. Shift into 3rd
8. Release clutch pedal
If you did it right, the shifter will slide effortlessly into place with no clicking or grinding sounds. If you followed the directions, but still met some resistance getting into 3rd gear, then you are blipping the throttle too much or too little.
When you blip the throttle with the car in neutral it causes the engine and transmission to move at the same speed. If you blipped it just enough, this speed will be the same as the axles, too, and everything will come together.
An important thing to realize is that the car is not in neutral if the clutch is in. The shifter must be in the middle of the transmission, and the clutch must be released for the car to be in neutral.
If someone has told you that double clutching is revving the engine while the clutch is in, they are wrong. That only does half of the work and does not get the transmission up to speed.
Here's a "diagram":
ENGINE-TRANSMISSION-AXLES/WHEELS
The transmission is right between the engine and the axles/wheels, so if you don't get the transmission moving, too, you're not double clutching.