Synchromesh Manual Transmission / Gearbox - How it Works

This video explains the operation of a typical manual transmission, detailing gear changes and synchromesh (blocker/baulk ring) operation. In some countries the manual gearbox is knows as Stick shift.
The Synchromesh AKA Constant Mesh gearbox is an improvement on the older sliding mesh gearbox which relied heavily on driver skill and double-clutching to not grind or crunch the gear change. The sliding mesh box was also known as a "crash box" due to the gears making lots of noise when changing.
The particular gearbox used in this video is the main case of a Land Rover LT77 but information applies to most manual transmissions in vehicles today.
To cut straight to the synchro action go to 4:25.
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Funcionamiento de la caja de cambios

[@anandcherian.585]

This is one of the best explanations.

[@sandermall]

Clear, no mucking about, the slightest touch of humour - the perfect explanation. Thank you for making this!

[@TanmayChhatbarR]

This video has to be one of, if not the best explanations to syncromesh gearboxes. Thanks.

[@TungstenCarbideProjectile]

The best by far

[@eznAnze]

This is indeed one of the best videos explaining the transmission working principle and synchromesh! The only thing which is missing is how the RPMs at the wheel hub are matched at the RPMs of the engine giving a practical examples with proper gear ratios! let's say 0.2m wheel radius, 3:1 differential gear ratio, 1st gear 3:1, 2nd gear 2:1, engine RPM range between 600 and 6000. 10km/h, 1st gear, wheels @ 135 RPM, engine @ 1215 RPM , tot ratio 9:1 -> switching to second gear the clutch separates engine from transmission but wheel speed remains constant, when 2nd gear is synchronised the transmission side of the clutch spins to a lower 810 RPMs accordingly to the new 6:1 tot ration -> releasing the clutch brings engine and wheels to a midpoint weighted by the relative inertial energies, considering flywheel mass

[@edsonsabino]

It's amazing. I've watched severeal computer animations about this topic. However watching the real thing happen made me understand it better Thank you!

[@LOOKINVERTED]

Having no use of my legs after an accident and my refusal to drive a wankomatic I learnt to crash the box when my installed 'servo clutch' decided to stop working. I always wondered how this was technically possible, driving with no clutch and it looks like it's all possible due to the synchromesh and how the bulk ring allows pressure from the driver and locks the gear up with friction enabling me to engage the gear once I've matched the engine-speed to road-speed. I'm presuming without synchromesh you'd have to judge the engine-speed to road-speed far more precisely (and quickly) otherwise gears would start crunching. Fantastic invention.. and explanation, thanks.

[@Sergio_Loureiro]

The Citroën DS is a car old as dinosaurs, and it already had automactic clutch. en.wikipedia.org/wiki/Semi-automatic_transmission#:~:text=The%20Citro%C3%ABn%20DS%2C%20introduced%20in%201955%2C%20used%20a%20hydraulic%20system

[@bigjoshlevine]

yep, seeing the real thing - and in slow motion - beats animation everytime! Thanks!

[@adamjc86]

Thanks for explaining why reverse doesn't behave as normal! Surprised me the first time I crunched the gear box when selecting reverse 😬

[@exdri]

I've spent my life looking for this video.

[@yaarge2]

Brilliant explanation....As commented by others, I found the use of a real gearbox and components much more informative than computer animation. Thanks for posting 👍

[@xdygmnyrdf]

Crazy good explanation. The youtube superstars like chrisfix and eric the car guy dont even come close. Thanks for sharing your knowledge!

[@mindsharping]

Great! I had never heard about Synchromesh until I watched a video on the Escort 30 min's ago. With this video and a dictionary, I think I now understand it so-so and I also have a constructive idea about how manual gears work. A great job since I eh.... usually struggle to grasp anything mech. Thanks!

[@rahulsoni5459]

the best video on synchromesh gearbox.🇳

[@johnlewis6412]

Thank you. Great explanation. I think I finally understand it. The slow motion piece really helped me get an idea of how it really worked.

[@personalfunfest]

Best explination -- real model beats CGI

[@autogc22]

The best explained I've seen so far. Congrats

[@thehoopsters5255]

My Dad said his Dad had Meccano when he was younger. So it's been around ages!

[@slyoldfox9288]

Brilliant! Simple explanation and funny narrative. Thank you!

[@Sckever]

best explanation ive seen, thank you!

[@ktex2877]

Great explanation!

[@EducationalMechanics]

Thanks Sam.

[@RamboRicardo007]

Smashing, explains very nicely. Thanks for taking the time to do a decent video.

[@Senkino5o]

Very well done.

[@EducationalMechanics]

Thanks Eli.

[@rafihussain]

Thanks for teaching

[@mikeyboy3054]

Outstanding explanation. Thanks!

[@EducationalMechanics]

cheers Mikey.🙂

[@lungonelias1836]

Mate by far ..the best explanation 💪👍👏👏👏😃 thanks alot

[@bryancrick640]

very well explained

[@edgurung4237]

lol tomorrow is my automobile exam and i am tryna learn from this vid

[@EducationalMechanics]

how did you get on in your exam?

[@accordinglyryan]

This was very nicely explained. Thanks!

[@EducationalMechanics]

Thanks Dell0304, that means a lot to us.

[@accordinglyryan]

You're welcome!

[@johncooke8857]

Fantastic Videos please keep up the good work! From Hastings Sussex England.

[@Pythnn]

So it's almost like a miniature clutch in there to spin up the dog gear. That's one of the most genius things I've ever seen

[@rdg6797]

Great info here, many thanks!.

[@mayosakka1146]

Man thank u so much bro u r amazing in explaining

[@fredinjoebenny4771]

Nice explanation

[@abonourabonour1006]

very interested I learned a lot from your chan channel thank you

[@cryptomaniacs5533]

Bravo!!!

[@KingKong-zp4ll]

Excellent, thanks

[@pa1264]

Awesome video thank you.

[@abhishek.jaiswal]

really nice explanation...could you also explain automatic transmission?

[@EducationalMechanics]

Thanks, automatic transmissions is on our to do list. That's quite a complex one.

[@louiehoehn3373]

Good video guys thank you!

[@EducationalMechanics]

We're glad you like it Louie, thanks for watching!

[@somrakphongoen2060]

Educational Mechanics

[@imnotabotrlyimnot]

It's very reminiscient of the Turbo Encapsulator.

[@luigir3022]

Thanks for this video. May I ask you some questions? When the first gear is engaged (at 1:58) the input shaft still rotates, now if the clutch is pressed and the car is not rolling the input shaft should slow down and stop as soon as the first gear is engaged isn't it? I have another doubt, in case where nothing is moving (I mean both input and output shafts are at rest) what ensures the alignment and the synchonization between the sleeve teeth and the blocking ring teeth or between the sleeve teeth and the gear teeth? Can those end up to a point-to-point condition and impede the engagement or the chamfer on the teeth will always make them sliding sidewise?

[@EducationalMechanics]

Hi Luigi, you're correct, when engaging 1st gear from stationary both the input and output shafts are likely to be stationary, it's only when the car is moving that the shafts would be moving (for our video using this training gearbox we couldn't get it to engage very well while stationary, so we had to make it move). You're correct, when both input and output shafts are at rest, the chamfer on the teeth of the blocking ring and the sleeve dog teeth allow the gear to engage by re-aligning itself. This can only happen if the synchromesh unit is not under any load or driving force. In some older cars where the points of the teeth have worn, you can experience a point-to-point condition that would impede engagement, but this can be overcome by momentarily lifting the clutch pedal to get the input shaft to move slightly. I hope this helps.

[@MaxPower-rp4qo]

Hi, thx for the explanation. I have a follow-up question to that. When my car is stationary (full standstill) and I fully press in the clutch and then shift to first gear, I sometimes get a sort of audible "thump" in the drivetrain when it goes into gear. Could it be that the clutch, even whilst it's fully pressed, allows a little rotation of the primary shaft so the gears mesh more easily at a standstill or is my clutch maybe getting worn and not a 100% de-clutching anymore? Thx for reply

[@kwunmeichan8013]

2:43, 3:33 blocker ring, 4:25 slow motion

[@michaelomalley4561]

Would a T45 transmission be considered older and not have Synchromesh?

[@chuckg9805]

Needed to show a little more info on how Main shaft is not connected to Imput shaft.

[@ROCKINGMAN]

So is there no need for a clutch?

[@TheRouteShow]

Please make a video on how gearshift happens with cable shifters in transaxle...I hve searched everywhere and still unable to understand how it works..

[@pohlr1]

how does the clutch ll play into this

[@leavemyrightsalone]

Nice!!!!

[@shree_7097]

you rock!

[@EducationalMechanics]

Thanks electrostatic. 😀

[@mcgrorymachined7596]

land rover LT77 gearbox?

[@EducationalMechanics]

Hi Callum, you've got it, we used a Land Rover LT77 box for this video.

[@andychow5509]

This is a good explanation as to why you can't shift into reverse. But I've also noticed I can't shift into first unless stationary, even if only going 5 kph. Does the first gear also not have a synchromesh?

[@BrownBomber92181]

On all of the manual cars I've driven and owned, when slowing down and shifting into 1st, I always shift into 2nd, then into 1st and it engages smoothly. It always seemed harder to get into first if I didn't go into 2nd first. It seems to line up the gears

[@jamieford8662]

Outstanding explanation but for one thing. While most gearboxes do not have Synchromesh on reverse the Aisin A6 does and I like that feature of my Lexus IS 200. Same gearbox is fitted to: Mazda RX 8 and MX 5 Nissan Sylvia Toyota Altezza

[@MailboxReviews]

Some heavier duty japanese cars does have reverse synchros as well (Mitsubishi Pajero/Montero/Shogun ) i got 2002 Pajero 3.0 V6 6G72 Engine with V5MT1 Transmission and it does have reverse Synchro 😊

[@deldirk7123]

nice one, 'blah blah blah' to cut out the science explanation and go to lay mans terms. Very informative. Electric transmissions are interesting too. Took me a long time to understand them as could not find a suitable book to explain electric transmissions fully

[@mayday478]

D.D.D.D.DROP THE BASS... err I mean clutch