Proper Downshifting Techniques!
Registered User
Joined: Feb 2002
Posts: 45
Likes: 0
From: Seattle
[QUOTE]Originally posted by REDGSR
[B]As far as I understand, there is a theoretical difference between simply rev matching and double clutching, but on most modern cars, double clutching is not necessary unless you really want to baby your transmission.
[B]As far as I understand, there is a theoretical difference between simply rev matching and double clutching, but on most modern cars, double clutching is not necessary unless you really want to baby your transmission.
Registered User
Joined: Oct 2001
Posts: 86
Likes: 0
From: Northern
Trackman, I'm pretty sure we are saying the same thing.....
so how are these different?, except for the fact that you state you don't need to disengage the clutch the second time (which wouldn't be double clutching then, would it?).
please read through the entire post next time instead of just screaming NO! NO! NO!
Oh, and I guess I should of added the sychros in the diagram, it should be:
motor-->clutch-->synchros-->primary gears-->output shaft (driven wheels)
From my earlier post...
OK. so, in double clutching... By disenageing the clutch, putting the car in nuetral, and letting out the clutch, now the motor is separated from the wheels because no gear is selected, but the primary gears are still linked to the motor. Now, when you rev the engine, you are bringing the entire primary gear set up to speed. Now you press the clutch again, put the car in the lower gear, the primary gears are already moving the correct speed
OK. so, in double clutching... By disenageing the clutch, putting the car in nuetral, and letting out the clutch, now the motor is separated from the wheels because no gear is selected, but the primary gears are still linked to the motor. Now, when you rev the engine, you are bringing the entire primary gear set up to speed. Now you press the clutch again, put the car in the lower gear, the primary gears are already moving the correct speed
Trackman
When you let the clutch pedal up and engage the clutch in neutral, you connect your synchros and rev up your whole transmission when you rev match. When you disengage the clutch and shift into a lower gear, your ENTIRE drivetrain is matched. In fact, you don't have to use the clutch at all if you match perfectly.
When you let the clutch pedal up and engage the clutch in neutral, you connect your synchros and rev up your whole transmission when you rev match. When you disengage the clutch and shift into a lower gear, your ENTIRE drivetrain is matched. In fact, you don't have to use the clutch at all if you match perfectly.
please read through the entire post next time instead of just screaming NO! NO! NO!
Oh, and I guess I should of added the sychros in the diagram, it should be:
motor-->clutch-->synchros-->primary gears-->output shaft (driven wheels)
Registered User
Joined: Oct 2001
Posts: 86
Likes: 0
From: Northern
Maverick,
I believe you are correct in saying that simple rev matching is not better than double clutching. This is correct, to a point. Any modern car has a synchromesh transmission. The job of the synchromesh is to speed up the primary gears to match that of the ouput shaft (or direct connection to wheels) as you shift gears (upshifting or downshifting) so that when the clutch is engaged, the speed of the trans is matched to the speed of the motor. This is what the synchromesh system was designed to do. The wear that keeps being mentioned is minimal at most because the gears already have a good amount of inertia already, the synchros are just bringing them to the correct speed.
[QUOTE]
Originally posted by Trackman
I believe you are correct in saying that simple rev matching is not better than double clutching. This is correct, to a point. Any modern car has a synchromesh transmission. The job of the synchromesh is to speed up the primary gears to match that of the ouput shaft (or direct connection to wheels) as you shift gears (upshifting or downshifting) so that when the clutch is engaged, the speed of the trans is matched to the speed of the motor. This is what the synchromesh system was designed to do. The wear that keeps being mentioned is minimal at most because the gears already have a good amount of inertia already, the synchros are just bringing them to the correct speed.
[QUOTE]
Originally posted by Trackman
Registered User
Joined: Aug 2001
Posts: 2,774
Likes: 1
From: Central USA
A few years ago (I'm showing my age), manual shift transmissions did not have any synchros on first gear. If you wanted to use first gear while the car was moving, you had to learn the double clutch procedure. If anyone wants to learn how to do this properly, find an older car that has no synchromesh on first gear. Once you can shift into first, while rolling without grinding, you will understand the process. 
Joined: Oct 2001
Posts: 3,216
Likes: 34
From: NM/CO
Just a quick note, double clutching was what you need to do to shift gears before the the synchronize transmission came out. as late as the 1980 (thats whenI quit driveing 18wheelers) you had to double clutch going up or down through the gears. In todays cars it is not really needed to change gears, just cool sometimes. Rev-matching can be done without double clutching.
Thread
Thread Starter
Forum
Replies
Last Post