When driving a car with manual transmission on start you slowly release the clutch so the car doesn't jerk. So clutch slippage here is not that bad if I understand this correctly?

And also couldn't dog clutch or synchromesh units be used as a mean of disconnecting the engine from the transmission? Then perhaps clutch could be used further down in a DCT to change between gears?

Thanks in advance.


Clutches in car transmissions are designed on purpose to allow slip transiently, to make gear changes and standing starts smooth. This is not a bad thing. But they are not designed to slip all the time, which would wear them out quickly and generate lots of heat.

It is possible to use the synchronizers in a motorcycle transmission to "bang" through the gears without using the clutch, but this is because the motorcycle weighs a lot less than a car and the synchronizers are stout enough relative to the weight of the bike to take this sort of punishment- for a while, anyway.

But this is decidedly not the case for cars and trucks, where this sort of abuse will ruin the synchronizers and eventually break the teeth off the gears.

  • $\begingroup$ Thanks for answering. $\endgroup$ – Dominik Serbinek Aug 26 '19 at 18:20
  • $\begingroup$ You can do "clutchless shifts" in a car or truck, too, if you know your shift points. You blip the throttle to unload the gears, go to neutral, then blip the throttle again to match the engine speed to the driveshaft speed, then slip the thing into gear. Before transmissions came with synchromesh it was pretty much the way to go (because without synchromesh you grind the gears on every shift, otherwise). $\endgroup$ – TimWescott Aug 26 '19 at 18:41
  • $\begingroup$ Seen good truck drivers (and done it myself) change gear clutchless, no need to “bang” either, just not as easy in a car as it is lighter... $\endgroup$ – Solar Mike Aug 27 '19 at 4:00

Should take you no more than 3 seconds to engage the clutch fully, then get your foot off the clutch pedal...

Some manual transmissions have hydraulic clutches inside the gearbox to enable changing between some gears (1&2, 3&4, 5&6 as those sets, while 2 to 3 etc need the use of the clutch pedal).

  • $\begingroup$ This isn't an answer to my question. $\endgroup$ – Dominik Serbinek Aug 26 '19 at 8:31
  • $\begingroup$ My first paragraph answers your first paragraph, the second ditto. Unless you have not expressed clearly that which you wish to ask... $\endgroup$ – Solar Mike Aug 26 '19 at 8:49
  • $\begingroup$ The questions are: Is it ok for clutch to slip in DCT in certain situations and that situation was described in paragraph 1. Second was if it was possible to use dog clutches or sync dog clutches in between engine and transmission, not inside transmission between gears $\endgroup$ – Dominik Serbinek Aug 26 '19 at 9:50
  • $\begingroup$ So put a dog clutch between a 2000hp engine doing 5000rpm and try connecting it to a stationary shaft - what do you think will happen? Do you have any idea? $\endgroup$ – Solar Mike Aug 26 '19 at 10:31
  • $\begingroup$ It will probably break but I don't know, that is why I'm asking. Also I am not talking about 2000hp engine which is unrealistic. I am yalking about everyday cars. $\endgroup$ – Dominik Serbinek Aug 26 '19 at 14:58

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