Transmission downshift forces - discussion..... Jim, Greg? comments?
07-27-2014, 04:06 PM
#1
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Transmission downshift forces - discussion..... Jim, Greg? comments?
Help me understand some thing about synchros and our transmissions.
Jim B, Greg B?
I have a high level understanding of the inter-workings of the transmissions, but this interaction below has me puzzled. i know we have discussed double clutching before, and the lack of need due to non -straight cut gears of modern gear boxes, as well as synchronizers that help spin up the layshaft on a downshift. but is it true that matching engine RPM doenst have anything to do with saving the synchros? I thought it lightened the load on them (and wear) considerably in a downshift. Lets talk , 80mph in 3rd to redline RPM match to get to 2nd. whats happening?
i know for a fact that without an RPM match, i cant even get the transmission into 2nd without a huge grind.
im thinking what is written below is wrong,because the RPM blip , spins up the drive shaft and input shaft when you let the pedal out, and this must help relieve the forces on the synchros, on spinning up the layshaft as you select the new gear, 2nd.
what am I missing. below, the poster makes it very clear, that engine RPM matching has nothing to do with saving synchros.
What was said on another discussion:
Rev-matching has NO effect on the synchros at all. None, zero, nada, zip. It does not help wear on the synchros, it does not help them do their job and it does nothing more than match engine speed to road speed.
A properly executed double clutch WILL spin the synchros up and help the tranny out.
Two different operations, two different effects. As a small matter of fact, in cars with super light flywheels and tiny clutches, two distinct blips are often necessary during double clutching: One with the clutch engaged (while in neutral) to spin up the tranny and then another a split second later (just prior to the second engagement) to affect rev-matching.
The odd thing is the fact that you actually KNOW all of this. I now believe you have either a reading comprehension problem, an attention issue, drink while posting, or otherwise don't care what others have to say; you merely stab words into the little reply box in an effort to continue the direction of whatever tangential debate the threads lead you.
Jim B, Greg B?
I have a high level understanding of the inter-workings of the transmissions, but this interaction below has me puzzled. i know we have discussed double clutching before, and the lack of need due to non -straight cut gears of modern gear boxes, as well as synchronizers that help spin up the layshaft on a downshift. but is it true that matching engine RPM doenst have anything to do with saving the synchros? I thought it lightened the load on them (and wear) considerably in a downshift. Lets talk , 80mph in 3rd to redline RPM match to get to 2nd. whats happening?
i know for a fact that without an RPM match, i cant even get the transmission into 2nd without a huge grind.
im thinking what is written below is wrong,because the RPM blip , spins up the drive shaft and input shaft when you let the pedal out, and this must help relieve the forces on the synchros, on spinning up the layshaft as you select the new gear, 2nd.
what am I missing. below, the poster makes it very clear, that engine RPM matching has nothing to do with saving synchros.
What was said on another discussion:
Rev-matching has NO effect on the synchros at all. None, zero, nada, zip. It does not help wear on the synchros, it does not help them do their job and it does nothing more than match engine speed to road speed.
A properly executed double clutch WILL spin the synchros up and help the tranny out.
Two different operations, two different effects. As a small matter of fact, in cars with super light flywheels and tiny clutches, two distinct blips are often necessary during double clutching: One with the clutch engaged (while in neutral) to spin up the tranny and then another a split second later (just prior to the second engagement) to affect rev-matching.
The odd thing is the fact that you actually KNOW all of this. I now believe you have either a reading comprehension problem, an attention issue, drink while posting, or otherwise don't care what others have to say; you merely stab words into the little reply box in an effort to continue the direction of whatever tangential debate the threads lead you.
07-27-2014, 09:23 PM
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Help me understand some thing about synchros and our transmissions.
Jim B, Greg B?
I have a high level understanding of the inter-workings of the transmissions, but this interaction below has me puzzled. i know we have discussed double clutching before, and the lack of need due to non -straight cut gears of modern gear boxes, as well as synchronizers that help spin up the layshaft on a downshift. but is it true that matching engine RPM doenst have anything to do with saving the synchros? I thought it lightened the load on them (and wear) considerably in a downshift. Lets talk , 80mph in 3rd to redline RPM match to get to 2nd. whats happening?
i know for a fact that without an RPM match, i cant even get the transmission into 2nd without a huge grind.
im thinking what is written below is wrong,because the RPM blip , spins up the drive shaft and input shaft when you let the pedal out, and this must help relieve the forces on the synchros, on spinning up the layshaft as you select the new gear, 2nd.
what am I missing. below, the poster makes it very clear, that engine RPM matching has nothing to do with saving synchros.
What was said on another discussion:
Rev-matching has NO effect on the synchros at all. None, zero, nada, zip. It does not help wear on the synchros, it does not help them do their job and it does nothing more than match engine speed to road speed.
A properly executed double clutch WILL spin the synchros up and help the tranny out.
Two different operations, two different effects. As a small matter of fact, in cars with super light flywheels and tiny clutches, two distinct blips are often necessary during double clutching: One with the clutch engaged (while in neutral) to spin up the tranny and then another a split second later (just prior to the second engagement) to affect rev-matching.
The odd thing is the fact that you actually KNOW all of this. I now believe you have either a reading comprehension problem, an attention issue, drink while posting, or otherwise don't care what others have to say; you merely stab words into the little reply box in an effort to continue the direction of whatever tangential debate the threads lead you.
Jim B, Greg B?
I have a high level understanding of the inter-workings of the transmissions, but this interaction below has me puzzled. i know we have discussed double clutching before, and the lack of need due to non -straight cut gears of modern gear boxes, as well as synchronizers that help spin up the layshaft on a downshift. but is it true that matching engine RPM doenst have anything to do with saving the synchros? I thought it lightened the load on them (and wear) considerably in a downshift. Lets talk , 80mph in 3rd to redline RPM match to get to 2nd. whats happening?
i know for a fact that without an RPM match, i cant even get the transmission into 2nd without a huge grind.
im thinking what is written below is wrong,because the RPM blip , spins up the drive shaft and input shaft when you let the pedal out, and this must help relieve the forces on the synchros, on spinning up the layshaft as you select the new gear, 2nd.
what am I missing. below, the poster makes it very clear, that engine RPM matching has nothing to do with saving synchros.
What was said on another discussion:
Rev-matching has NO effect on the synchros at all. None, zero, nada, zip. It does not help wear on the synchros, it does not help them do their job and it does nothing more than match engine speed to road speed.
A properly executed double clutch WILL spin the synchros up and help the tranny out.
Two different operations, two different effects. As a small matter of fact, in cars with super light flywheels and tiny clutches, two distinct blips are often necessary during double clutching: One with the clutch engaged (while in neutral) to spin up the tranny and then another a split second later (just prior to the second engagement) to affect rev-matching.
The odd thing is the fact that you actually KNOW all of this. I now believe you have either a reading comprehension problem, an attention issue, drink while posting, or otherwise don't care what others have to say; you merely stab words into the little reply box in an effort to continue the direction of whatever tangential debate the threads lead you.
However, the closer one can match the speed of the gear that is going to be engaged to the speed of the syncro it is being used to engage that gear, it's pretty obvious that wear is going to go down at an incredible rate.
Simply look at a common downshift:
The pinion is obviously rotating at the speed required by the ring gear, for the speed the vehicle is going....they are all mechanically connected and unable to be disconnected (unless something breaks.)
The layshaft, 5th gear, the torque tube shaft, the clutch disc, and the engine are all turning the speed required for the gear currently selected.
When a downshift is desired, the layshaft, 5th gear, the torque tube shaft, the clutch, and the engine rpms must be increased.
Once the clutch is depressed, the engine is temporarily out of the equation....but the clutch, the torque tube shaft, 5th gear, the layshaft, and the "new lower ratio" gear must all have their speed increased. Without increasing that rpm with the engine, the only way to do this is by the syncro increasing the speed as it slides over the "new lower ratio gear".
Pretty simple stuff.
Obviously, the less work the syncro needs to do (increasing the speed with the engine, instead of totally by the syncro) the less wear there will be on that syncro.
I have no idea of who made the statement that "matching has NO effect on the syncro at all. None, zero, nada, zip", but his understanding of what is happening isn't nearly as good as his writing....
Respectively, he's completely wrong.
gb
07-27-2014, 10:04 PM
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Mark, unless you're paraphrasing the old discussion, I can't find the verbiage you've quoted anywhere in the archive. Got a link to the prior thread?
07-28-2014, 01:04 AM
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Its one of those things you really have to think about. I know there is a factor that is made up of the synchros bringing up the layshaft speed, to the new gear speed, and by matching the revs on to what will be the new speed, i thought that would take more than half the work out of the synchros. better to spin up some idle gears and shafts, than the entire driveline , when decoupled from the engine.
Its the nightmare brake question thread on the racing forum. Was looking at some real life comparisons for my issues, and all i got was a bunch of meat head debates that cant read more than one sentence before they retort... and usually with a half baked or wrong answer, that either completely misses the mark or is missing several key factors.
Well....the writer certainly seems really sure of what he thinks....
However, the closer one can match the speed of the gear that is going to be engaged to the speed of the syncro it is being used to engage that gear, it's pretty obvious that wear is going to go down at an incredible rate.
Simply look at a common downshift:
The pinion is obviously rotating at the speed required by the ring gear, for the speed the vehicle is going....they are all mechanically connected and unable to be disconnected (unless something breaks.)
The layshaft, 5th gear, the torque tube shaft, the clutch disc, and the engine are all turning the speed required for the gear currently selected.
When a downshift is desired, the layshaft, 5th gear, the torque tube shaft, the clutch, and the engine rpms must be increased.
Once the clutch is depressed, the engine is temporarily out of the equation....but the clutch, the torque tube shaft, 5th gear, the layshaft, and the "new lower ratio" gear must all have their speed increased. Without increasing that rpm with the engine, the only way to do this is by the syncro increasing the speed as it slides over the "new lower ratio gear".
Pretty simple stuff.
Obviously, the less work the syncro needs to do (increasing the speed with the engine, instead of totally by the syncro) the less wear there will be on that syncro.
I have no idea of who made the statement that "matching has NO effect on the syncro at all. None, zero, nada, zip", but his understanding of what is happening isn't nearly as good as his writing....
Respectively, he's completely wrong.
gb
However, the closer one can match the speed of the gear that is going to be engaged to the speed of the syncro it is being used to engage that gear, it's pretty obvious that wear is going to go down at an incredible rate.
Simply look at a common downshift:
The pinion is obviously rotating at the speed required by the ring gear, for the speed the vehicle is going....they are all mechanically connected and unable to be disconnected (unless something breaks.)
The layshaft, 5th gear, the torque tube shaft, the clutch disc, and the engine are all turning the speed required for the gear currently selected.
When a downshift is desired, the layshaft, 5th gear, the torque tube shaft, the clutch, and the engine rpms must be increased.
Once the clutch is depressed, the engine is temporarily out of the equation....but the clutch, the torque tube shaft, 5th gear, the layshaft, and the "new lower ratio" gear must all have their speed increased. Without increasing that rpm with the engine, the only way to do this is by the syncro increasing the speed as it slides over the "new lower ratio gear".
Pretty simple stuff.
Obviously, the less work the syncro needs to do (increasing the speed with the engine, instead of totally by the syncro) the less wear there will be on that syncro.
I have no idea of who made the statement that "matching has NO effect on the syncro at all. None, zero, nada, zip", but his understanding of what is happening isn't nearly as good as his writing....
Respectively, he's completely wrong.
gb
07-28-2014, 01:39 AM
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I thought the new gear selected ,and main 5th gear shaft , torque tube and clutch, would have to be spun up to the high speed that the flywheel and engine are now spinning at. You go through neutral, and then the synchros are doing all the work to spin up the 5th gear, (main shaft), torque tube and clutch . in thinking about it, i see where the poster is coming from. but, because of what i feel in rev matching downshifting, im thinking as you let out the clutch, you do it as its going into gear, to help spin up the torque tube, and lessen the load on the synchros. now, that im thinking about it.......... is he completely wrong?
certainly a valid question.
I think thats it.... its the letting out of the clutch, slightly ahead of the gear engagement that spins up the high mass elements of the clutch, driveline and 5th gear main shaft, and the appropriate gear. you do this very quicky and no one really recognizes it. because if you do it slowly..... rev the engine and then wait (say you are holding the RPM at 6000rpm for example). you select the gear and complete the shift, then release the clutch.... all the work was done by the synchros and rev matching wouldnt help get it into gear smoothly. (just wont chirp the tires when you release the clutch now).
thoughts?
certainly a valid question.
I think thats it.... its the letting out of the clutch, slightly ahead of the gear engagement that spins up the high mass elements of the clutch, driveline and 5th gear main shaft, and the appropriate gear. you do this very quicky and no one really recognizes it. because if you do it slowly..... rev the engine and then wait (say you are holding the RPM at 6000rpm for example). you select the gear and complete the shift, then release the clutch.... all the work was done by the synchros and rev matching wouldnt help get it into gear smoothly. (just wont chirp the tires when you release the clutch now).
thoughts?
07-28-2014, 02:18 AM
#6
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Amateur engineer's take on the subject at hand-- And yes, I have assembled one or two gearboxes over the years.
The original poster is correct when he says that rev matching -alone- has no effect on synchro wear or duty. A single-clutch downshift disconnects the engine from the synchro action, leaving, as Greg point out, all the other spinning bits from clutch disk to 5th gear layshaft spinning at a speed that starts at pre clutch disengagement engine speed and decreases due to bearing friction. To actually increase the speed of the driveline between the flywheel and the 5th gear layshaft, you must execute a clutch disengagement, gearbox to neutral position. clutch re-engagement, blip the throttle to bring the driveline speed up to what you expect to need in the gear you are going to select, then disengage the clutch again, select that next gear while either holding target engine speed, or blipping to restore that speed, then re-engage the clutch in the 'new' lower gear.
The goal is to have the synchronizers do as little work as possible. That means speeds of input and output are matched pretty well when you select the next gear. A 'normal' downshift has the synchronizers loading to speed up the driveline bits to match the input speed in the new gear. The double-clutch blip in neutral with clutch engaged does that part of the synchronizer's duty. From that point, "rev matching" limits the slip in the clutch before full engagement, and may help limit the possible traction upset when the engine is suddenly brought to speed as the clutch engages. It also helps save half-shafts and CV joints under extreme circumstances.
The original poster is correct when he says that rev matching -alone- has no effect on synchro wear or duty. A single-clutch downshift disconnects the engine from the synchro action, leaving, as Greg point out, all the other spinning bits from clutch disk to 5th gear layshaft spinning at a speed that starts at pre clutch disengagement engine speed and decreases due to bearing friction. To actually increase the speed of the driveline between the flywheel and the 5th gear layshaft, you must execute a clutch disengagement, gearbox to neutral position. clutch re-engagement, blip the throttle to bring the driveline speed up to what you expect to need in the gear you are going to select, then disengage the clutch again, select that next gear while either holding target engine speed, or blipping to restore that speed, then re-engage the clutch in the 'new' lower gear.
The goal is to have the synchronizers do as little work as possible. That means speeds of input and output are matched pretty well when you select the next gear. A 'normal' downshift has the synchronizers loading to speed up the driveline bits to match the input speed in the new gear. The double-clutch blip in neutral with clutch engaged does that part of the synchronizer's duty. From that point, "rev matching" limits the slip in the clutch before full engagement, and may help limit the possible traction upset when the engine is suddenly brought to speed as the clutch engages. It also helps save half-shafts and CV joints under extreme circumstances.
07-28-2014, 02:42 AM
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Dr. Bob always can explain what I try to explain, much better! He is exactly correct. Unless there is a double clutch effort made, to accelerate the disconnected pieces, the sycros get "no relief".
Most racers are not capable of a quick double clutch, allow the syncro to do all the work, and simply blip the throttle to accelerate the "disconnected" engine, in order to "save" the connecting rods and bearings.
Not to make this more confusing than it is, but perhaps worth noting is that the Borg Warner design syncros are hooked to and have the same speed as the pinion shaft. The "early Porsche design" syncros are attached to the individual gear and rotate at those speeds....
Most racers are not capable of a quick double clutch, allow the syncro to do all the work, and simply blip the throttle to accelerate the "disconnected" engine, in order to "save" the connecting rods and bearings.
Not to make this more confusing than it is, but perhaps worth noting is that the Borg Warner design syncros are hooked to and have the same speed as the pinion shaft. The "early Porsche design" syncros are attached to the individual gear and rotate at those speeds....
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07-28-2014, 06:38 AM
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Part of this also can depend on how the clutch is used. Is the clutch being fully depressed to the point where there is absolutely no interaction between the flywheel / pressure plate combination and the clutch disk? If so then the syncro probably is doing all of the work when downshifting. If the clutch is only being depressed far enough to remove the majority of the friction, but not enough to completely separate all the clutch components and prevent all energy transfer, then rev-matching would probably have a tangible impact on syncro wear and shifting. Depending on how a specific combination of clutch parts actually fit together and are adjusted, there may end up being some amount of energy transfer regardless of how the clutch pedal is depressed.
07-28-2014, 05:28 PM
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so, the OP, was right and not "completely wrong"?
erioshi.... thats what i was trying to say too. just enough drag so that it spins up the driveline as you pass through neutral, doing the same effect as double clutching for all practical purposes.
Dennis can!
do a test. with engine at 40mph , try and put the car in 1st gear from neutral and clutch pushed in...... ahhhhhhh.. now do this by blipping the throttle. big diff,smooth shift.
but if there is residual drag friction, which there always seems to be, wouldnt that spin up the driveline before the gear is selected as you pass through neutral?
im also thinking about simultaneous shifts, where the revs are up and the gear is engaged as the clutch is released. a timing thing that does it all at once that spins things up via both the engine and synchros?
erioshi.... thats what i was trying to say too. just enough drag so that it spins up the driveline as you pass through neutral, doing the same effect as double clutching for all practical purposes.
Dr. Bob always can explain what I try to explain, much better! He is exactly correct. Unless there is a double clutch effort made, to accelerate the disconnected pieces, the sycros get "no relief".
Most racers are not capable of a quick double clutch, allow the syncro to do all the work, and simply blip the throttle to accelerate the "disconnected" engine, in order to "save" the connecting rods and bearings.
Not to make this more confusing than it is, but perhaps worth noting is that the Borg Warner design syncros are hooked to and have the same speed as the pinion shaft. The "early Porsche design" syncros are attached to the individual gear and rotate at those speeds....
Most racers are not capable of a quick double clutch, allow the syncro to do all the work, and simply blip the throttle to accelerate the "disconnected" engine, in order to "save" the connecting rods and bearings.
Not to make this more confusing than it is, but perhaps worth noting is that the Borg Warner design syncros are hooked to and have the same speed as the pinion shaft. The "early Porsche design" syncros are attached to the individual gear and rotate at those speeds....
do a test. with engine at 40mph , try and put the car in 1st gear from neutral and clutch pushed in...... ahhhhhhh.. now do this by blipping the throttle. big diff,smooth shift.
Part of this also can depend on how the clutch is used. Is the clutch being fully depressed to the point where there is absolutely no interaction between the flywheel / pressure plate combination and the clutch disk? If so then the syncro probably is doing all of the work when downshifting. If the clutch is only being depressed far enough to remove the majority of the friction, but not enough to completely separate all the clutch components and prevent all energy transfer, then rev-matching would probably have a tangible impact on syncro wear and shifting. Depending on how a specific combination of clutch parts actually fit together and are adjusted, there may end up being some amount of energy transfer regardless of how the clutch pedal is depressed.
Amateur engineer's take on the subject at hand-- And yes, I have assembled one or two gearboxes over the years.
The original poster is correct when he says that rev matching -alone- has no effect on synchro wear or duty. A single-clutch downshift disconnects the engine from the synchro action, leaving, as Greg point out, all the other spinning bits from clutch disk to 5th gear layshaft spinning at a speed that starts at pre clutch disengagement engine speed and decreases due to bearing friction. To actually increase the speed of the driveline between the flywheel and the 5th gear layshaft, you must execute a clutch disengagement, gearbox to neutral position. clutch re-engagement, blip the throttle to bring the driveline speed up to what you expect to need in the gear you are going to select, then disengage the clutch again, select that next gear while either holding target engine speed, or blipping to restore that speed, then re-engage the clutch in the 'new' lower gear.
The goal is to have the synchronizers do as little work as possible. That means speeds of input and output are matched pretty well when you select the next gear. A 'normal' downshift has the synchronizers loading to speed up the driveline bits to match the input speed in the new gear. The double-clutch blip in neutral with clutch engaged does that part of the synchronizer's duty. From that point, "rev matching" limits the slip in the clutch before full engagement, and may help limit the possible traction upset when the engine is suddenly brought to speed as the clutch engages. It also helps save half-shafts and CV joints under extreme circumstances.
The original poster is correct when he says that rev matching -alone- has no effect on synchro wear or duty. A single-clutch downshift disconnects the engine from the synchro action, leaving, as Greg point out, all the other spinning bits from clutch disk to 5th gear layshaft spinning at a speed that starts at pre clutch disengagement engine speed and decreases due to bearing friction. To actually increase the speed of the driveline between the flywheel and the 5th gear layshaft, you must execute a clutch disengagement, gearbox to neutral position. clutch re-engagement, blip the throttle to bring the driveline speed up to what you expect to need in the gear you are going to select, then disengage the clutch again, select that next gear while either holding target engine speed, or blipping to restore that speed, then re-engage the clutch in the 'new' lower gear.
The goal is to have the synchronizers do as little work as possible. That means speeds of input and output are matched pretty well when you select the next gear. A 'normal' downshift has the synchronizers loading to speed up the driveline bits to match the input speed in the new gear. The double-clutch blip in neutral with clutch engaged does that part of the synchronizer's duty. From that point, "rev matching" limits the slip in the clutch before full engagement, and may help limit the possible traction upset when the engine is suddenly brought to speed as the clutch engages. It also helps save half-shafts and CV joints under extreme circumstances.
im also thinking about simultaneous shifts, where the revs are up and the gear is engaged as the clutch is released. a timing thing that does it all at once that spins things up via both the engine and synchros?
07-28-2014, 08:53 PM
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but if there is residual drag friction, which there always seems to be, wouldnt that spin up the driveline before the gear is selected as you pass through neutral?
im also thinking about simultaneous shifts, where the revs are up and the gear is engaged as the clutch is released. a timing thing that does it all at once that spins things up via both the engine and synchros?
07-28-2014, 09:12 PM
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Guys,
As some may know, there were not always synchronizers. Early "crash boxes" mostly in trucks, required "double clutching" as it was called, for both up shifting and downshifting.
One could get really good at it and shift quite quickly.
I believe most really early cars were this way.
My sons were also quite impressed when I drove my 911 home many miles with a broken clutch cable. Start in first, match RPMs and shift to third, then to fifth. Really have to work the traffic and signal lights. Ease into neutral and coast/brake to a stop. Repeat until home.
Dave
As some may know, there were not always synchronizers. Early "crash boxes" mostly in trucks, required "double clutching" as it was called, for both up shifting and downshifting.
One could get really good at it and shift quite quickly.
I believe most really early cars were this way.
My sons were also quite impressed when I drove my 911 home many miles with a broken clutch cable. Start in first, match RPMs and shift to third, then to fifth. Really have to work the traffic and signal lights. Ease into neutral and coast/brake to a stop. Repeat until home.
Dave
07-29-2014, 04:12 AM
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So this is where having the clutch adjusted well, and having a good pilot bearing make sense. If your driveline has your "residual drag", the synchros get to pull the driveline to speed, plus absorb whatever energy is transmitted through via that drag. In your shift-to-first example, there's more "residual drag" than the synchro clutches can manage. Speed up the driveline by whatever means, and the synchros don't have as much energy to transfer.
Yes, if the clutch isn't completely disengaging.
What is a "simultaneous shift"?
Yes, if the clutch isn't completely disengaging.
What is a "simultaneous shift"?
something is going on to make such a difference, even in a well adjusted clutch pack. (and you know i know something about that!~
)im thinking that a slight out of adjustment is good, and helps the situation, OR, it might be a style of shifting that alows for some contact of the clutch to the driveline during the shift that spins things up. like double clutching, without double clutching.
like this. you put the clutch in to take it out of gear and move to neutral, but you dont put your foot all the way in. we all do this.. its easy, because you dont need much clutch to put in neutral. THEN, as you pass through neutral, you blip and the push a few mm farther and make the nice clean shift. during which, the driveline was spun up. everyone wins, no harm done, synchros saved, and you didnt even know you were doing anything special!
07-29-2014, 04:16 AM
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Guys,
As some may know, there were not always synchronizers. Early "crash boxes" mostly in trucks, required "double clutching" as it was called, for both up shifting and downshifting.
One could get really good at it and shift quite quickly.
I believe most really early cars were this way.
My sons were also quite impressed when I drove my 911 home many miles with a broken clutch cable. Start in first, match RPMs and shift to third, then to fifth. Really have to work the traffic and signal lights. Ease into neutral and coast/brake to a stop. Repeat until home.
Dave
As some may know, there were not always synchronizers. Early "crash boxes" mostly in trucks, required "double clutching" as it was called, for both up shifting and downshifting.
One could get really good at it and shift quite quickly.
I believe most really early cars were this way.
My sons were also quite impressed when I drove my 911 home many miles with a broken clutch cable. Start in first, match RPMs and shift to third, then to fifth. Really have to work the traffic and signal lights. Ease into neutral and coast/brake to a stop. Repeat until home.
Dave
remember...a slight dragging clutch, is murder to get in first or 2nd. doesnt even go in. But once you are moving, shifting is like nothing is even wrong. the forces are so light dynamically. (just cant do reverse and 1st from a stop). get the car rolling and it slides right in. this is why i think the little force of not fully depressing the clutch pedal at downshift time, ,keeps some engagement, but not enough to effect anything. then, a throttle blip, spins up the driveline, because this little drag easily does that. then the shift, which now all parts are synchronized.
07-29-2014, 11:57 AM
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