Synchronizer Operation Explained

[@5CGQ]

What most people don't appreciate is that "grinding gears" isn't damaging the actual gears that transmit power, but the dog teeth on the synchro system.

[@DrivelineMaster]

You are absolutely correct.

[@dangeary2134]

Makes me appreciate that big truck transmissions generally do not have synchronized gearsets. I had to rebuild an entire transmission when someone had broken the main output shaft in one. No books, no drawings, nothing but brute competence. I will say, the way that they are made with dual or triple countershafts, the design is ingenious. The input and output shaft are only connected by a pilot bearing. The fact that the main output was snapped into two pieces, and the transmission didn’t fly apart is testament to the designer! The countershafts held the gears in their proper location, even though the shaft was toast! No synchronization there, just a good gear matching hand was required!

[@mikekokomomike]

I have a Kawasaki motorcycle and the factory service manual chapter on repairing the transmission has one line about " paying attention to the mating dogs ". Made me chuckle.

[@josephschaefer9163]

Not if you have old stuff with slider gears

[@josephschaefer9163]

@Franky997 grinding gears on old stuff like '47 chevy, farmall tractors, or cub cadet lawn mowers does damage the actual gear teeth. The whole gear slides to engage

[@jptrainor]

Best and only video of a synchronizer in live operation that I've seen.

[@getplaning]

I have overhauled countless gearboxes, measuring gaps and replacing parts, but this is the best explanation of how a gearbox works that I have ever seen.

[@DrivelineMaster]

Thanks for the compliment.

[@anthonygonzalez-oit9299]

This was really well explained. The video at the end really capped it off and pulled it all together for me. Thanks.

[@ComMando9100]

I wish teachers at school would teach the same way. Amazing video with lots of different presentations, I don't think this could be explained any better than this!!!

[@sarthak_18]

Really sir you said true thing

[@rogergummer5173]

Given the hard job, its a reasonably good explanation.

[@132_pradyumnajoshi8]

The cleanest explanation of synchro that I have ever seen. No other video that I have referred has explained the functioning of the key, which in my opinion, brings the whole thing together. Kudos!👏

[@DrivelineMaster]

Thank you. Most comments are similar to yours. I do occasionally get one from someone who is real picky or they just like to knock me down. I appreciate the positive comment.

[@OverlyCuriousEngineer]

One of the best videos i have ever watched about synchro mechanism. Incredible presentation.

[@DrivelineMaster]

Thank you

[@maneki9neko]

Yes. He really has all the fine details down. Gear boxes for Spec Miata racing are rebuilt all the time. However the re-builds tend to have problems. If a rebuilder replaces the bearings, the brass synchro rings, and the seals then the gearbox will shift into gears easily and the box will hold oil, but will it stay in gear? Apparently if the back-cut (2:15 in the video) on the engagement teeth between speed gear and synchro sleeve are worn, these parts need to be replaced too. Someone who is simply installing a 'rebuild kit' will miss this.

[@maneki9neko]

This is terrific. Details like the back cut on the engagement teeth on both the synchronizer sleeve and the speed gear, are new to me. This is shown under magnification at 2:15, and is easily missed when you have the parts in your hand. This back cut is what holds the two parts together under load, and prevents the car from popping out of gear. When an older transmission pops out of gear people will tell you with authority and confidence: 'oh, the synchronizer rings are bad'. But the synchro rings have little to do with this function. However when this tiny back cut, on on the engagement teeth of the speed gear or the synchronizer sleeve is worn away, there is nothing left to hold speed gear and sleeve together. In this case a new set of synchro rings will do nothing to fix the problem. And that is very much worth knowing.

[@DrivelineMaster]

Thank you for your comments. Please note that the back cut is not present on all synchronizer sleeves and gears. I see it missing mostly on older transmission designs. There are several reasons why a transmission will jump out of gear and worn out back cut is one of them. Normally what happens is the oil is not changed when it should be and or the driver is rough on the transmission and the blocker rings start to wear causing grinding (gear clash) which in turn chews up the clutching teeth on the gear and on the sleeve which wears away the back cut. It's often a domino effect.

[@mikes9939]

Would be good to explain that the synchro ring is made of brass hence it's gold color. Brass is softer and is sacrificial meaning it will eventually wear out and need replacement. Brass is the perfect companion metal to press against the hard steel gear and do no damage to it as it tries to either speed it up or slow it down so the the synchro hub can slide over and complete the lockup. It's important to remember that the synchronizer assembly must adjust the speed of the entire cluster gear and input shaft including clutch disc in order to perform the lockup into the selected gear. Quite a task and shows why you must have clean clutch release so that the disc is completely free to rotate. This is a very good video, especially with the gear train illuminated with the strobe light to show what happens.

[@DrivelineMaster]

Thank you for your good comments. You are correct. One note. although these blocker rings are brass there are other blocker rings made of other materials and sometimes either lined with a friction material similar to brake lining and others that use a bi-metal design with a sintered metal inner cone that is soft with a high coefficient friction. I will consider a followup video with this additional information.

[@shaggydogg630]

We had some Mustangs rings made of paper! Replaced many.

[@Kevin-mx1vi]

​@@Franky997Can confirm that because some years ago I worked for a company that made synchromesh rings for many of the major European car manufacturers. Selector forks were also made from phosphor bronze, but of a different grade.

[@trumanhw]

@@shaggydogg630 of ... paper? No joke? No, has to be a joke. Sounds impossible.

[@shaggydogg630]

@@trumanhw compressed paper , no joke.

[@Danielagostinho21]

Using a strobe light to see gears at speed mesh, Brilliant!

[@mathewshackelford8037]

Works just like a timing light

[@maxwelld3753]

Never understood how they worked until I watched this. Very well done.

[@gleambrite2679]

You always think there must be an easier way. Loads of engineering and sleepless nights have gone into all these details to run smooth operations. Amazing and well explained. Great work.

[@jerryscared]

Great video! Wonderful explanation. I especially appreciated the summary in the beginning of the three functions of the synchronizer.

[@LEDRavecom]

Wow, using the strobe light to show synchronizer at work is brilliant! Thank you!

[@spacetrace7021]

The ability or willing to show what you explaining just earned you a subscriber.

[@elora2525]

The best video for ASE, I watched this video 2 times before the test and still didn't pay enough attention. This video need to be watch 3 times for ASE manual transmission test

[@gsheverything_2716]

Why the test, if you don't mind me asking???

[@xavieraxiak6866]

As the sleeve moves towards the speed gear, the keys weakly push the blocking ring ahead until the conical friction surfaces make contact. The resulting frictional torque rotates the blocking ring so that it's teeth are 1/4 tooth pitch misaligned with the sleeve teeth which causes contact of the teethes' angled surfaces. This is called "energizing". As well as causing the blocking teeth to block the sleeve, the sleeve can now apply a strong force to the blocking ring via the tooth contact, increasing friction and synchronizing torque.

[@abhijeetchilwirwar722]

A great video , actually had doubts about the internal shafts used and the sleeve and gear engagement but this video had it all covered

[@chadportenga7858]

Thank you! The demonstration of the synchro in action at 7:00 helps it all make sense. (The first part of the video is the nitty gritty of what makes it work. The demo shows it in action.)

[@OwensGarage]

Excellent video, thank you. You just filled up another small gap in my mechanical knowledge.

[@NickGiamattiKeyWest]

Fantastic presentation!....Great technical detail & functional explanation! Strobe light visual on the Rotating System really brought-it-all- together! Thank you!

[@Kimbeattie]

Great video and the strobe light showing the operation was brilliant thanks from Canada

[@sleekSquirrel]

the strobe light detail was above and beyond and really helped explain it thank you so much

[@DrivelineMaster]

Thanks. I too thought that was a great technique to display moving parts.

[@sleekSquirrel]

@@DrivelineMaster I still dont understand how the sleeve will not engage the gear until the gear speeds are in sync??

[@DrivelineMaster]

This is a very valid question and not an easy concept to understand so let me give this explanation a try. When the sleeve is forced in the direction of the gear to engage then next gear the keys will push on the blocker ring which pushes on the gear. Friction and heat is generated between the blocker ring and the gear. With the heat expansion forces occurs. This expansion from the heat creates a force that pushes the blocker ring and keys back against the sleeve. This force makes it difficult for the sleeve to continue in the direction of the gear until everything is in sync or very close to being in sync. When everything is in sync the friction, heat and resistive force is reduced to a point where the sleeve can now easily slide over and engage with the gear. I hope this makes sense.

[@sleekSquirrel]

@@DrivelineMaster thanks. I did more research today i found that the mass/inertia of the constant mesh gears trying to be slowed by the blocker ring will force the splines to be out of alignment (and unable to engage) until the gear speeds are in sync. Only then can the tapered splines be aligned by the driver pulling the shifter because there is no longer any force "binding" the splines

[@DrivelineMaster]

That is the reason the blocker ring can't immediately synchronize the rotational speed of the gear with the sleeve however it is the friction and the expansion forces that prevent the sleeve from moving over to attempt to lock onto the gear while they are rotating at different speeds.

[@Anglgrinder-j3y]

Thank you for explaining & animating, this technology is becoming clearer, thank you

[@DORVALFAGUNDES]

Drivemaster, you're the best Master. My language is Portuguese, but I didn't understand the Brazilian videos and I understood your video. I didn't understand how the synchronized ring works but thank for you, I understand now.

[@DrivelineMaster]

Your Welcome

[@kengarcia1461]

Really good, well explained and easy to understand demonstration. Thanks for making and sharing this video

[@chimeragaming56]

really nothing beats a good explanation and some actual footage or hands on with my actual hands. ty for this.

[@doublebass3858]

very good explanation. The only video I found that explains the synchronizing gear in great detail

[@DrivelineMaster]

I'm glad this worked out for you.

[@jabberwockytdi8901]

Still the best video on KZbin on this subject

[@DrivelineMaster]

Thank you. This is one of my top videos.

[@Bushybowl]

Excellent job on the video, structured and explained perfectly and pleasure watching

[@diegorodriguez-lk8of]

Great fucken video don't give up you'll be up to 1 million subscribers soon. Best of luck and thanks for making things clear and simple to understand

[@aniruthdinesh9156]

Awesome Presentation, now I understand how this really works!

[@frankcastle8349]

Thanks for the video! An excellent explaination,best on YT for gears.

[@johnpower8356]

Great with strobe, I had a 1958 Mack truck when I was young no syncro’s man you had to shift just right, you get used to it. Great video

[@Joeelectronicschematicsforauto]

This was absolutely awesome these videos should be in schools to teach students

[@DrivelineMaster]

They are used in all my classes.

[@dalekrinke2674]

Very good explanation of this mechanism. Thank you a bunch for your time and experience! 👍👍

[@Limeayy]

Woo, this time Manual Transmissions. If i literally had an instructor that taught like this I think it'd go into my head alot easier :P

[@pablogarciavasquez6637]

¡EXCELLENT MASTER CLASS AND GREAT TEACHER GREETINGS FROM LIMA PERU!

[@BugCrush3r]

excellent description of the synchronizer but I wish you talked a bit more about the locking keys and springs and the purpose they serve

[@DrivelineMaster]

They are not locking keys. They are synchronizer keys. They transfer the force between the sleeve to the blocker ring.

[@lovesjw]

Applause! Real gentlemen applaud this good video!

[@katojeremiahcsfg4274]

Liked the way you tried everything to make us get the idea, thanks

[@nickayivor8432]

Thanks for sharing what you know with us brilliant video tutorial amazing From Nick Ayivor from London England UK 🇬🇧

[@cncn9631]

Its Amazing teach Video I Ever Seen. Good Jobs

[@billglenn10]

Excellent video and explanation of how this works... Thank you...

[@Engineerboy100]

Wow!!!! That was awesome 👌 thanks you so much for posting.

[@WilliamStrawnJoe]

Any time I think I am smart, I need to watch this and realize how much I don’t know.

[@ervinmq1955]

Great Vid. Well explained... Thanks for sharing...

[@JIm-w1b]

Kids used to say they could drag race powershift as in brute force abuse without using the clutch, but the way the synchronizer is designed, this is impossible, because the harder you try to force a shift, the harder the synchro will ride up onto the cone and fight to prevent it

[@keitharoo1962]

Wow, did I just learn something today!!!! Thanks!!!

[@raymondjames9734]

i want to use this to make a fixed gear / free wheel bicycle hub! never understood this before thank you!

[@ScottsGarage17]

Great job explaining!

[@abdullahmohammed2955]

Amazing video thanks alot hope u r having a beautiful life ❤

[@larrydykes7643]

Somebody needed to show this video to my old '67 VW bug.

[@kalef1234]

That strobe demo was great

[@federicomezzina5784]

Thank you for the very clear explanation!

[@elwoodgalapagos1846]

gotta love the reverb on the voice

[@LibertyWarrior68]

I'm getting ready to rebuild my gearbox, so I'm learning as much as I can.

[@trumanhw]

I'll point out that everyone praising how clear this video is then goes on to describe all the transmissions they've rebuilt. So as the only person who's here to learn instead of to see what they already know, I'll say that I completely disagree about the clarity. This is supposed to be about SYNCHRONIZERS / synchromesh. Instead, it's about the entire transmission. Yes, I see that it happens. But I still don't understand what mechanism is locking it. Is it the conical taper? Is it a friction surface? Don't know -- we moved on to naming over half the various components of a transmission without explaining what they are ... which means only people who already know the information will brag about it's clarity. While you're at it, why not define a word using the word you're defining? Do syncros require a particular alignment? Or can they synchronize in any orientation? As in ... they aren't uniform. So does it require at least 1 full rotation to align features? Also ... why can't syncros grind? Because of the taper at the front of the teeth ..? What's the purpose of the conical taper? Is that what synchronizes the mechanism? (Why not spend a little extra time explaining how/when it occurs with each of the mechanisms to drive home the principle that the video was TITLED?) If it's the teeth meshing ... then why don't synchros need synchros? The taper / conical interaction with a friction coating makes sense as to why it wouldn't need synchros. But why would those teeth as animated synchronize without grinding any better than the gears we're synchronizing? When the only people praising your edu are those who are all practical application valedictorians, you should be concerned that you didn't make the content as _introductory_ as your title suggests. There are many fields in which I have expertise, and when I try to explain them to others, the main thing I focus on is the avoidance of jargon, of relying on predicate knowledge that the only people who need the information wouldn't have, and on remembering what it was once like to not know those things; because it's that _empathy for ignorance_ that is lost with the very expertise required to explain the content. Mind you, this was by far better than all the other videos I've yet watched on syncros. So please don't take it as a blanket critique across the board. And clearly, great effort went into this production (and corresponding animation) ... which couldn't have been cheap in either time, money or expertise. All of which I'm grateful for, as this is free content. Please don't mistake my critique as ingratitude. I'm just unwilling to lie and pretend I've gone from being ignorant to being knowledgeable (even rudimentary) from watching it 5-6 times.

[@DrivelineMaster]

I'm sorry this missed the mark for you and all those who are learning but are not familiar with the terminology. A goal of mine is to try and keep the videos high quality and as short as possible and if I have a long winded subject to make it into multiple parts. As someone watching who has not had some formal transmission training or rebuild experience I need to let you know that this is by far not how the entire transmission works and it truly is just about synchronizer operation. A fair amount of viewers have never rebuilt a transmission (Like your) but they may have had some formal training or they are attending a class on manual transmissions and the video helps to clarify what they didn't understand from their instructor. With that said I will try to address your operational questions. The conical tapered surfaces between the gear and the blocker ring when pressed together create friction which will attempt to make them rotate at the same speed which if successful will synchronizing the speed between them. What is not shown is the shift fork, rod, gate, detent, interlock and shifter. Yes, I know these are technical terms that are not defined. Basically these components are responsible for moving the sleeve which pushes on the keys which push on the blocker ring in an effort to synchronize the gear to the blocker ring and synchronizer assembly so a gear ratio change can be made. These videos are about detent and interlock mechanisms and they may help. kzbin.info/www/bejne/sGi0madprrSZesksi=6cY5W393OPiiq1xL and kzbin.info/www/bejne/i2iwc5R_hdSDkJYsi=CFUVtq0YD9ehFlXk. What holds the gear into engagement (Sleeve locked onto the gear) is a combination of the shifter position (which moves the shift rod, fork and sleeve), the detent mechanism, and the cutback design on the clutching teeth on the gear and sleeve. (Timestamp 4:10.) Synchronizers can be mounted vertically and function but most manual transmission with synchronizers tend to be horizontal in operation. They do not require one full revolution to synchronize and they will work if the vehicle is stopped or going very slow such as in a parking lot (going from reverse to 1st) or during stop and go heavy traffic. The goal of the synchronizer is prevent grinding and it does this by using the friction between the blocker ring (rotating at shaft and synchronizer assembly speed) and the gear rotating at a different speed. Once the two are in sync the clutching teeth between the sleeve and the gear are close enough in alignment to allow the sleeve to move over (from force of the driver pushing on the shifter) locking the two together. The transmission is now locked into the new gear ratio and held there by the design of the clutching teeth and the shifter and detent mechanism and position. If, or when the blocker ring surface wears to a point where it's incapable of providing efficient synchronization grinding between the clutching teeth on the sleeve, blocker ring and gear will take place and can be heard when the driver shifts gears. This is called "Gear Clash". If these teeth become heavily worn down the transmission will pop out of gear (The shifter will move all by itself into neutral) under heavy acceleration. The shifter and detent alone are unable to maintain gear engagement when the clutching teeth are heavily worn from driving a vehicle that has excessive gear clash during shifting. In summary: the conical surface does the synchronization when the shifter is moved but it's not strong enough to handle the torque of the gear ratio. This is why the clutching teeth on the sleeve need to engage and lock onto the clutching teeth on the gear. The synchronizer sleeve is moved through a mechanical shift mechanism when the driver moves the shifter to change gears. The shifter mechanism, detent (see video links) and clutching teeth keep the gear engaged until the driver moves the shifter again for the next gear selection. This was my attempt to clarify your operational questions. The video is what it is and your critique is noted. If you have additional technical operational questions I'm happy to answer them. You might also find these videos helpful. Into to manual transmission power flow and gear ID: kzbin.info/www/bejne/l3KqaZ6arJaKe80si=MU8s5wGrDLMKGcZ6 Front wheel drive manual transaxle shifter mechanism: kzbin.info/www/bejne/pZXdhKhsbp6hoNUsi=G2QMd06MzFJxzvpd These videos may also have similar critiques from you since my videos are all designed to support my lectures and assume a minimal amount of automotive transmission nomenclature knowledge. I will keep this in mind when creating new technical content and make an effort to clarify a technical term into everyday language when I feel that it is needed and it won't make the video too long unlike this response.

[@AndreKK-]

Best video on the topic!

[@DrivelineMaster]

Thank you.

[@fjs1111]

You did phenomenal work putting this together and your explanations. Learned a few things.

[@DrivelineMaster]

Glad you enjoyed it and found it of value.

[@Tedminat0r]

Brilliant idea with the strobe light. Thanks!

[@skudnu5462]

so, synchronization only works when the car is moving since we need the gears to be spinning correct? engaging first gear from a standstill therefore does not need to be synchronized just like reverse?

[@DrivelineMaster]

Pretty much correct, the synchronization only takes place when the gears are spinning. Even though the car is not moving if your engine is running and the trans is in neutral but vehicle is not moving some of the gears inside the transmission are spinning. If you push the clutch pedal to the floor and move the shifter quickly some synchronization might take place. If on the other hand after you push the clutch pedal to the floor you wait about 30 seconds before moving the shift lever then all the gears will most likely be stopped.

[@stimpsonjcat67]

Damn fine job on the strobe use!

[@MrsTiaRani]

awesome video, very well explained! many thanks

[@m.b.smoshitoa8325]

WONDERFUL MY MAN. I DID NOT UNDERSTAND THIS BEFORE BUT NOW I HAVE THE GUTS TIO GO OPEN GEARBOX. LOL MOSHITOA ( S AFRICA)

[@charleskutrufis9612]

Thank You for this video. Very informative.

[@RC-Heli835]

That is so cool to see it working like it should. My KW T800 has an 8LL and its synchroniser has been very noisy since the heat exchanger went bad and got water into the transmission.

[@DrivelineMaster]

Try Changing the oil and put Redline Manual Transmission Fluid (MTF) in it. This stuff does wonders sometimes.

[@RC-Heli835]

@@DrivelineMaster I just have changed the incorrect 90 wt for 50 wt motor oil. That by its self worked wonders. It made it possible to where the gear shift would actually move the gears in and out. Before that I could take it out of gear and it would stay in gear. It did that one morning until the oil got warm. I ran it all day, came in and drained that 90 wt while hot and its been better ever since. Everything but the synchroniser. So mine is not slowing the gear down when all that noise is going on? I wonder if the air shifter could be sticky somehow?

[@DrivelineMaster]

Unless the manufacture says you can use motor oil instead of GL4 or GL5 gear oil I wouldn't leave the 50st motor oil in your transmission. 90wt gear oil is not the same as it would be if it was 90wt motor oil. The way they measure thickness for gear oil is different than motor oil. Once again I would recommend the Redline MFT. I know it cost more but it is worth it. Unless your transmission was designed to work with motor oil (like some honda's) you will end up damaging your transmission and costing you more $$$ in the long run.

[@RC-Heli835]

@@DrivelineMaster It calls for 50 wt engine oil. Granted Synthetic would be better but we just had a cracked head replaced at 6,389.00 on the truck and now the compressor has blown apart on the other truck leaving us stuck with a core fee. Cat wants 1,500.00 just for the core fee alone. Fleet Pride got us a refurbished for little over a grand and no core charge.

[@DrivelineMaster]

As long as the factory specification is 50wt engine oil then that is what you should use and have confidence that you won't cause any damage. This is the first trans that I know about that uses 50 wt straight motor oil.

[@SFlores1979]

This video was great!!! Thank you for it.

[@vusindlovu8897]

Simply beautiful 👌

[@TheAnonymous1one]

Question: Since the small clutching teeth is what mechanically locks the free spinning speed gear to the shaft and actually transfers the power why dont we see more of those stripped vs the actually gear teeth on high powered cars? It looks like it has much less material engagement would seem to be the weak link. I would also think the narrow sleeve that couples the two together would be prone to strip out before the actual speed gear teeth would strip under high power.

[@DrivelineMaster]

1) the small clutching teeth are already 95% in alignment with the teeth on the gear before the sleeve is allowed to slide onto the gear so there is no grinding. This is accomplished by the proper operation of the blocker ring. When the blocker ring becomes worn out and can no longer perform properly that is when the clutching teeth start the grind during the shift. This is the grinding noise that can be heard by the driver between shifts and is called gear clash. The reason these tiny teeth can handle the torque comes from the total surface area contact between the gear and the sleeve. The number of teeth and the length of the teeth determine the total contact surface area. I'm not an engineer but this is something that has to be engineered into the design. They must determine the maximum torque that the synchronizer and gear would have to be able to handle and how much contact is needed.

[@brianb-p6586]

Between two gears, only one tooth on each gear is engaged with the other gear at any time. Between the parts of the synchronizer assembly, all of those small teeth are engaged at the same time, spreading the load out between them. Many small teeth are as strong as one large tooth.

[@ryanhewett1663]

very informative; thank you.

[@luca490]

Beautiful video sir.

[@rogerbegin9479]

That was pretty interesting. I never knew how any of that worked.

[@heavydieselmechanic]

Good work

[@jafersadique7492]

Very informative 👍👍

[@utkarshkushwah8800]

Thanks for the such a nice explanatary video...

[@JohnSmith-ok9sn]

Exceptional video. Thank You!

[@DrivelineMaster]

John Smith from Plymouth, MI?

[@georgespangler1517]

Thanks,,,great informative vedio of the operations

[@jamingagnier2170]

Homie sounds like Kermit the frog

[@armedfarm3429]

After several videos trying to figure this out, I finally get it. Excellent video. Now I wonder if there would be other ways to slow shaft/gear speed. Synchro's are spendy parts "labor wise" to replace. I also wonder what fluid would cause the least amount of wear & still give satisfactory shifting.

[@DrivelineMaster]

Unless a specialized fluid is specified and the spec is 75w-90 or 80w-90 GL4 I really like Redline Manual Transmission Fluid (MTF)

[@josephschaefer9163]

Good ole stinky 80-90 gear lube is the highest temp rated fluid

[@armedfarm3429]

Up here in MN maybe a 75-85 would be a good choice. I think up in the cold states an ATF is hard to beat. @@DrivelineMaster

[@DrivelineMaster]

I don't want to give the wrong information. Most manual transmissions can not and should not use ATF. ATF can only safely be used in a manual transmission if and only if the service information or owners manual says so. Never use ATF in a manual transmission unless it has been specified by the manufacture as an acceptable winter oil option.

[@andrewhanson5942]

Now THAT is some high tech mechanical engineering!

[@larryanderson8049]

Not many explanations go into the importance of the key springs and tapers that let the pressure build against the friction ring and bring the gears to the same speed. Then suddenly snap and engage the teeth.... to me that is the most important function of the syncro.

[@ayiideng5857]

thank you for its very explained and helpful

[@shouliangzhang3333]

The best video to explain synchronizer. But I am a little confused, why did the sychronier blocker ring slow down the speed to snchronize with speed gear? It should be reversed, I mean, speed gear speeds up to sych with blocker ring.

[@DrivelineMaster]

When the transmissions is in 1st gear and you shift into 2nd gear (upshift) the speed of 2nd gear is rotating faster because the gear ratio for 2nd gear is a small ratio number such as 1st being 4:1 and 2nd being 3:1. Because the speed of 2nd gear is rotating faster than the output shaft and the synchro in 1st gear the 2nd gear must slow down to match the speed of the synchro and output shaft before it can engage and lock 2nd to the shaft. This happens with every gear change during upshifting. During downshifting this is reversed. The output shaft is going faster than the gear being downshifted into. Such as going from 4th at 1:1 down to 3rd at 2:1. Now when the blocker ring grabs the next lowest gear that gear will need to rotate faster or speed up to match the output shaft speed in order to synchronize. I hope this made sense. Also, those gear ratios are not actual but instead just used as examples to make a point.

[@asemelsayed9477]

amazing work but what is the speed of the blocking ring ? is it equal to shaft or gear speed before synchronizing?

[@DrivelineMaster]

The synchronizer hub which is splined to a shaft, the sleeve and the blocker ring all rotate at shaft speed.

[@asemelsayed9477]

@@DrivelineMaster ok thanks is the key connected rigidly to the blocker ring? and how are they connecting? and how does the blocking ring return its original position?

[@mrbigheart]

thank you, sir. this is highly useful!!

[@jacobwarrington1904]

Thanks for the video! Helped me study.

[@shanilkadesilva65]

Great video

[@ericbanks6644]

Fantastic video. Thanks!

[@isabelgarcia891]

Thank you great explanation

[@johng69er]

Great clear video thank you

[@deepsinghania6496]

This video is clear my concept

[@jimcopeland4011]

One perhaps ignorant question on the final demonstration. What is the gear on the far left of the video? I assume it looks like the speed gear, and maybe I'm not adequately understanding the relationship between the speed gear and the speed gear clutching teeth.

[@DrivelineMaster]

I believe that was 1st gear speed gear. The speed gear and the speed gear clutching teeth are all part of one gear assemble. The speed gears area also the free spinning gears check out from time stamp 2:44 to view the speed gear AKA free spinning gear.

[@pacman7959]

Hi, so I have a problem with getting the car into 1st gear sometimes. It can be very hard to push it in but no grinding. This would suggest it's the blocker ring doing it's job and the synchroniser and main shaft gear aren't matching speeds. I've checked the slave and master clutch cylinder and I can't see anything that stands out. Do you have a clue what's going on. Shifting into all other gears seems fine. I also have to hold the clutch down for around 10 seconds before I can put the car into reverse without grinding gears. It just seems like a long time before the layby shaft slows down. Clutch actually feels solid and operating as it usually does. Any ideas.

[@DrivelineMaster]

A couple of questions when you have problems going into 1st. Is this when the vehicle is not moving or when downshifting while moving? or both? Have you tried replacing the lubricant with the recommend fluid? Because you said that you have to wait a good 10 seconds to shift into reverse makes me think you might have a spin down problem. This is where power from the engine continues to send power into the transmission input shaft even if the clutch pedal if fully pressed. What can happen is one of a few things. The clutch disk can stick to the flywheel, or the disk could bind on the input shaft and not slide away from the flywheel quickly enough, or the input shaft could be binding on the pilot bearing. All of these will delay clutch disengagement and cause hard shifting. I'm not sure what vehicle you have but I have had good luck using Redline Manual Transmission fluid solving shifting problems.

[@maxenielsen]

Marvelous! Thank you so much!

[@jimc6481]

Thanks you, excellent video and explanation.

[@roadintersection]

I always find synchronizer ring is made of brass, not other metal. Is it the specifications?

[@DrivelineMaster]

They can be and are made out of other material. Some use a bimetal combination with a sintered bronze and brass material on the inside and steel on the outside. Others use steel and bond a friction material like a brake pad to the inside circumference. It's material that will work soaked in oil.

[@user-id3tj1gs6y]

Great video! The one part that I don't understand - how does the blocker ring prevent engagement if the gears cannot be synchronized?

[@DrivelineMaster]

Here you go. The sleeve pushes on the keys which push on the blocker ring. The job of the blocker ring through friction between the ring and the gear is to grab the gear and make it go the same speed (synchronize) so the sleeve can slide over and lock the two together. If the blocker ring is unable to synchronize the gear to its speed a lot of friction is taking place. With more friction more heat is generated. With more heat there is expansion of components. The heat and expansion is a counter force pushing back on the blocker ring. That force on the blocker ring is transferred to the keys and then onto the sleeve. The counter force prevents the sleeve from moving close enough to the gear for the clutching teeth to touch. If the clutching teeth are allowed to touch before synchronization a grinding noise (gear clash) will be heard. Hope this helps.

[@jokermanthemechanic]

Hay I have a 2008 dodge ram 1500 with a manuel 238 Getrag 6speed transmission in it. I'm have the same problem with second gear. Where can I find the parts for a 238 getrag and can I replace it with another manuel.

[@DrivelineMaster]

Unfortunately I don't have a source for that transmission. I once had a Getrag from a Toyota Supra and not even Toyota sold replacement parts short of an entire transmission. You can try West Coast Standard or midwest trans (www.midwesttrans.com/product-information/getrag-238-6-speed-rebuilt-manual-transmissions). try searching the internet using "getrag 238 rebuild kit" as your key words.

[@5speedMax]

That is a very cool visual.