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> Eventually I taught him how to double-clutch, rev-match when downshifting, and even how to float the shift with no clutch at all. Most of these things are un

> Eventually I taught him how to double-clutch, rev-match when downshifting, and even how to float the shift with no clutch at all. Most of these things are unnecessary and damaging to a synchronised manual. They aren't saving wear on any part of the transmission. About the only useful application of changing gear without using the clutch when the clutch cable fails. Unless you are in a manual American truck or a very old British one (the European trucks had synchros). Those are rapidly going to automated transmissions these days in any case.

rzzzt 4y ago
First gear and reverse are occasionally unsynchronized on old cars. And should you ever get into a Trabant: in 4th gear you get no engine brake, it's freewheeling!
- VBprogrammer 4y ago
  I originally said modern manual car but that felt like an oxymoron.
- mauvehaus 4y ago
  That's common on cars with 2-stroke engines that are lubricated by oil in the fuel (like a chainsaw). If you don't freewheel it, there's not enough oil coming through the fuel system to lubricate the engine properly. Old Saabs with 2-stroke engines were like that too.
mauvehaus 4y ago
As I understand it, matching revs makes for smoother shifting and reduces wear on the clutch plate. It also prevents a weight transfer from shifting, which is why Nissan did it in software on the 370Z. If you're about to fling a car into a corner, it behooves you to not upset the balance by shifting carelessly. Again, AIUI. I don't track anything. Double-clutching reduces the speed difference between the shafts that the synchros have to absorb, thereby reducing wear. It also lets you shift faster on track, or at all in a car with cranky synchros. The '86 BRAT I used to own was very leisurely about the 3-2 downshift without double clutching, and downright lethargic from 2-1. If you wanted to be ready to pull away from a stop sign promptly, double clutching it into 1st as you rolled to a stop was necessary. I can see shifting without the clutch adding wear to the synchros, but I've definitely had to do that too when the clutch went out on the '76 TR6 I used to own. Which admittedly had a very forgiving transmission, thank goodness. Meanwhile, I haven't put enough miles in our '47 CJ-2A to master a smooth 2-1 downshift without grinding the gears, even with double clutching. That promises to take some practice. Practice that'll have to wait until the steering is sorted well enough to get it inspected, plated, and get it up to 3rd on a paved road. 2nd gets it moving quite quickly enough, thank you very much. Rereading this before posting makes it sound like I've owned only terrible cars. I assert that they have character, and that's what matters. And only the BRAT was a daily driver. Apart from it, my daily drivers have all been pretty reliable and sensible cars.
Wistar 4y ago
Rev match, double-clutch, float, are all a part of the art of a manual, necessary or not. They're fun. Done correctly, I seriously doubt any are any more damaging to a synchronized manual than regular old shifting.
- VBprogrammer 4y ago
  Floating gears in a synchronized manual is just abusing the synchronizers as a clutch, if you get it right it's only a few rpm but why risk it? There is literally no advantage. Race car gearboxes like crashboxes and unsynchronized sequential gearboxes have stronger gear dogs with more backlash (bigger gaps between the dogs) to allow them to be shifted without synchronization. Double clutching is pointless. Just putting more wear on the throwout bearing.
  - Wistar 4y ago
    I have been doing all these horribly, scandalously abusive things all my life and have yet to replace a manual gearbox or have a throwout bearing fail prematurely (or at all).
  - fargle 4y ago
    floating doesn't even involve the synchro's unless you mismatch the rpm. there's no practical advantage, but it's not abuse either unless done very poorly. it's just fun to practice. anyway, if you just double clutch 1/2 the time and float the rest, your net throw-out bearing wear would be the same. ;-)
NLPlatypus 4y ago
What is this myth? Double clutching saves your synchros and takes the load off of them. Try it with any manual and you can feel much less effort shifting.
- VBprogrammer 4y ago
  The only thing it's doing is doubling the wear on the throw out bearing and clutch linkages. I've seen taxis with 300k miles on their 3rd clutch but never having any gearbox components changed.
  - Wistar 4y ago
    Not that wikipedia is the end-all, be-all authority on double-clutching. "While double clutching is not necessary in a vehicle that has a synchronized manual transmission, the technique can be advantageous for smoothly upshifting in order to accelerate and, when done correctly, it prevents wear on the synchronizers which normally equalize transmission input and output speeds to allow downshifting." https://en.wikipedia.org/wiki/Double_clutching_(technique) https://en.wikipedia.org/wiki/Double_clutching_(technique)
- Wistar 4y ago
  This is true, the gearbox almost sucks the next gear in. I often do it when taking first gear while rolling at a low speed.
ddingus 4y ago
I taught that in case of cable failure. Knowing what can happen and what one can do is important! Same goes for no brakes! What are the options? Downshift Turn engine off. (Deffo practice that one) Emergency brake. Take exit, side road, shoulder... Controlled crash. That last one saved me. Was in a '73 beetle on a racing slot type freeway and boom! No brakes and about 20 seconds before I arrived at what would be a wall of cars. No exits. No e-break. Shit! I ground the car to a stop. Literally. Downshifted, then engine off, then ease it into the wall... Scary and it trashed a nice beetle, but slamming into the other cars was gonna be way worse.

rzzzt 4y ago

First gear and reverse are occasionally unsynchronized on old cars. And should you ever get into a Trabant: in 4th gear you get no engine brake, it's freewheeling!

VBprogrammer 4y ago
I originally said modern manual car but that felt like an oxymoron.
mauvehaus 4y ago
That's common on cars with 2-stroke engines that are lubricated by oil in the fuel (like a chainsaw). If you don't freewheel it, there's not enough oil coming through the fuel system to lubricate the engine properly. Old Saabs with 2-stroke engines were like that too.

mauvehaus 4y ago

As I understand it, matching revs makes for smoother shifting and reduces wear on the clutch plate. It also prevents a weight transfer from shifting, which is why Nissan did it in software on the 370Z. If you're about to fling a car into a corner, it behooves you to not upset the balance by shifting carelessly. Again, AIUI. I don't track anything. Double-clutching reduces the speed difference between the shafts that the synchros have to absorb, thereby reducing wear. It also lets you shift faster on track, or at all in a car with cranky synchros. The '86 BRAT I used to own was very leisurely about the 3-2 downshift without double clutching, and downright lethargic from 2-1. If you wanted to be ready to pull away from a stop sign promptly, double clutching it into 1st as you rolled to a stop was necessary. I can see shifting without the clutch adding wear to the synchros, but I've definitely had to do that too when the clutch went out on the '76 TR6 I used to own. Which admittedly had a very forgiving transmission, thank goodness. Meanwhile, I haven't put enough miles in our '47 CJ-2A to master a smooth 2-1 downshift without grinding the gears, even with double clutching. That promises to take some practice. Practice that'll have to wait until the steering is sorted well enough to get it inspected, plated, and get it up to 3rd on a paved road. 2nd gets it moving quite quickly enough, thank you very much. Rereading this before posting makes it sound like I've owned only terrible cars. I assert that they have character, and that's what matters. And only the BRAT was a daily driver. Apart from it, my daily drivers have all been pretty reliable and sensible cars.

Wistar 4y ago

Rev match, double-clutch, float, are all a part of the art of a manual, necessary or not. They're fun. Done correctly, I seriously doubt any are any more damaging to a synchronized manual than regular old shifting.

VBprogrammer 4y ago
Floating gears in a synchronized manual is just abusing the synchronizers as a clutch, if you get it right it's only a few rpm but why risk it? There is literally no advantage. Race car gearboxes like crashboxes and unsynchronized sequential gearboxes have stronger gear dogs with more backlash (bigger gaps between the dogs) to allow them to be shifted without synchronization. Double clutching is pointless. Just putting more wear on the throwout bearing.
- Wistar 4y ago
  I have been doing all these horribly, scandalously abusive things all my life and have yet to replace a manual gearbox or have a throwout bearing fail prematurely (or at all).
- fargle 4y ago
  floating doesn't even involve the synchro's unless you mismatch the rpm. there's no practical advantage, but it's not abuse either unless done very poorly. it's just fun to practice. anyway, if you just double clutch 1/2 the time and float the rest, your net throw-out bearing wear would be the same. ;-)

NLPlatypus 4y ago

What is this myth? Double clutching saves your synchros and takes the load off of them. Try it with any manual and you can feel much less effort shifting.

VBprogrammer 4y ago
The only thing it's doing is doubling the wear on the throw out bearing and clutch linkages. I've seen taxis with 300k miles on their 3rd clutch but never having any gearbox components changed.
- Wistar 4y ago
  Not that wikipedia is the end-all, be-all authority on double-clutching. "While double clutching is not necessary in a vehicle that has a synchronized manual transmission, the technique can be advantageous for smoothly upshifting in order to accelerate and, when done correctly, it prevents wear on the synchronizers which normally equalize transmission input and output speeds to allow downshifting." https://en.wikipedia.org/wiki/Double_clutching_(technique) https://en.wikipedia.org/wiki/Double_clutching_(technique)
Wistar 4y ago
This is true, the gearbox almost sucks the next gear in. I often do it when taking first gear while rolling at a low speed.

ddingus 4y ago

I taught that in case of cable failure. Knowing what can happen and what one can do is important! Same goes for no brakes! What are the options? Downshift Turn engine off. (Deffo practice that one) Emergency brake. Take exit, side road, shoulder... Controlled crash. That last one saved me. Was in a '73 beetle on a racing slot type freeway and boom! No brakes and about 20 seconds before I arrived at what would be a wall of cars. No exits. No e-break. Shit! I ground the car to a stop. Literally. Downshifted, then engine off, then ease it into the wall... Scary and it trashed a nice beetle, but slamming into the other cars was gonna be way worse.