How Does a Torque Converter Work? 

I'm 60 years old and I finally understand how a torque converter works. THANK YOU

I watched a few other videos on TC and was generally confused, but this tied it all together for me. You're a true teacher because you put thought into choosing words, examples and demonstrations that are practical and appropriate for the audience. Well done, you should consider a career in teaching.

That fan demo was genius! Very good job explaining this!

You are so knowledgeable. You are a gifted teacher. As an engineer myself, I find your videos super informative. Keep up the great work.

I've taken a college course on auto trans... this was much more informative in 20 mins than the 3 months it took my teacher to do nearly the same.

This is by far the best instructional video of a torque converter I have ever seen. I am not a mechanic by any means, but his visual aids really lets you see how everything works. If Eric is an instructor in school, he must be putting out some "REALLY" good mechanics.

That was well done. I started out in automotive engineering. When starting out, there is a big difference in the rpm between the impeller and turbine. The impeller is then acting like a centrifugal pump accelerating the fluid to the outside and at an angle against an opposing angle on the turbine blades which are not spinning, making them a bit like a bucket on water wheel to extract some of the kinetic energy after which it is routed to the stopped or lower velocity inner diameter of the turbine, and back toward the inner diameter of the impeller where it will be sucked in and accelerated again. However, with the large difference in velocity and the opposite angle, the remaining kinetic energy opposes the impeller so there can be no torque gain unless you redirect and reuse that energy with a stator to assist the impeller. The stator attempts to rotate backwards and it cannot because the sprag/roller/one-way clutch doesn't allow it to, and it redirects the fast-moving fluid into the direction of the impeller at to further accelerate the fluid, which is where you get torque multiplication, ~2:1. However, as the turbine rpm gains equilibrium with the impeller, the turbine now produces its own back pressure from centrifugal force, thereby mostly balancing this out. However, with the angle of the inner turbine blades plus the rotation of the turbine being almost as fast as the impeller, the stator will now rotate with the impeller and turbine to give the best flow. This point is called couple or lockup, although it is not really coupled or locked up, but it will be less than 10%, slower depending on the converter, and torque multiplication will be 1:1. Thus, max torque multiplication occurs when the impeller is turning and the turbine is stopped. If something is wrong with the stator and it rotates in both direction, acceleration will be poor. If it won't move in either direction, it will add a load on the engine during coupling and cause heat buildup. Then came lockup torque converters where they actually do lock the impeller and turbine together physically, so they tend to refer to the former as couple rather lockup. The difference between a torque converter and a fluid coupling is the stator, which enables the multiplication of torque. So are fluid couplings obsolete? No. They are used in a lot of applications to isolate vibration between driving and driven members, and even gentle startups when an engine is running at a fixed RPM like electric engines and fluid is slowly added such as to start a conveyor belt with tons of product on it. The stall speed is the maximum rpm that the engine can turn when using all of its power against a stopped turbine. Logically, that depends on how much torque the engine has. While true, with something relatively heavy such as transmission fluid, small changes in RPM make big changes in torque to make a small rpm change, so it won't vary by as much as you think, which is why they can categorize them by stall speed. You can also see that the smaller the diameter, the faster you will have to spin it to equal the same outside velocity to achieve the same centrifugal force and pumping action on the fluid plus they have less area on the blades so a 1" difference in diameter can make a substantial difference in stall rpm. The stall rpm will vary more with torque variations as well, but still not by a lot. Of course the First Law of Thermodynamics states that neither matter nor energy can be created or destroyed. When the engine creates all of that high velocity fluid against a stationary turbine, the energy has to be dissipated somewhere, and it is. The engine horsepower is converted to heat, which is why the transmission cooler in the radiator, unless you have a wimpy engine in which fins on the outside of the converter and air holes in the bellhousing can do the job. Larger diameter converters are more efficient even during coupling. However, when overdrive transmissions and higher gear ratios became more and more popular, engine rpm dropped near or below where coupling would occur even at speed, so there were efficiency losses with more power going up in heat in the converter. This made the move to lockup converters compelling. From automotive engineering to aviation mechanic to military pilot, the engines made perfect sense to me right away because they use a stator to similar effect as torque converter except jet engines don't allow the stators rotate with the rotors because it is always pumping, unlike a torque converter, thus unnecessary. Another difference is the stators are where the compression is occurring when it converts the kinetic energy into static pressure, and redirects the flow direction into the rotor blades of the next stage. Torque converters don't compress the fluid but rather add to the kinetic energy to be expended against the turbine by feeding accelerated fluid back into the impeller to be further accelerated.

I'm a 50 year transmission master rebuilder, well done, I know how it works but I enjoyed watching you video, I give you a 100%.

I have been a diy person all my life and worked on my own cars, I fully understood all about the engine function and how it all worked together but until now have never known how a torque converter worked and why it was needed, just took it for granted and never tried to understand it because i couldn't see inside the sealed unit and now it is exposed and the knoledge you have shared is priceless for people like myself. well done!!

"i hope this video can help you in some small ways" dude. BIG. IT HELPED ME BIG. I NEVER understand how TC works but the fan demo you showed was really genius and that contributes to 100% of my understanding. Thank you ! you're the best !

Almost 8 years later this is still the best video on how these Donuts work. Thanks!

It's one thing to understand how this all works, but you really have to tip your hat at the guy who thought it up in first place.

Your practical gave me the "AHA!". 10/10.

I'm a geezer and throughout my entire life (thus far) I've never had a clue how torque converters work. Outstanding video, I loved the two fans demo, excellent. Thanks a ton, now I can pass my thanks through a torque converter and virtually double my thanks.. so thanks two tonnes.

This is amazing, your attention to detail and terminology, the clear and thorough explanations, that practical demonstration. You're an amazing educator!

I've watched you for almost 10 years and this is one of my favorite videos I have ever seen, in forms of technical knowledge and visual aid. I understood how TC's worked but could never explain it to another person myself. Always saw it as a compontent that just needed replaced as a whole and never got into the guts of it. Eric you're a legend

I am not a mechanic, i just like to know how things work. I watched this to the end and feel like i have actually learned something. Well done!

Best explanation I've seen so far of how a torque converter works. Really appreciate how you took a complicated subject and broke it down so that a layman could understand it. Your a good teacher.

My 1993 Oldsmobile started stalling at stoplights all of sudden. Thought I had a big problem. Finally got the car home after pissing off a whole lot of drivers behind me. Turned out to be the converter lockout solenoid. Part was $20, solenoid was under the transmission cover on the driver's side. Was a fairly simple repair and car was back to normal. A very small part that caused a big headache on the road. Excellent video by the way.

And I'm 75 years old, and think this is one of the best mechanical and physics presentations I've ever seen. Thank you!

What a time we live in, that we can just look this stuff up for free at any time, anywhere

The Physics is so well done, I had a idea about this as a kid , but this is so straightforward 😊 Well done Eric 😂

This was the most educational video on torque converters that I have ever seen. In fact, all your videos are so clear and concise. Thank you and keep being awesome.

True engineering. No computers. All brains and thinking and manual calculations.

No BS. Clear, concise, articulate, no jokes or talking to the dog. Well presented with fan analogy. Thanks for your effort and thoughtful presentation. Thanks for not wasting my time. You Tube channelers need to learn these techniques. I am subscribing.

Awesome video! I've never really understood torque converters until I watched this video! Thank you!

I've seen tons of TC explanation videos but this one trumps them all, easily. Well done.

Thank you for explaining it. You know you're a great teacher if you can explain something complex and advanced in a simple and easy to understand way.

This is probably the best write up I've ever seen on TC operation. Awesome job Eric. The fans are a really nice visual aid.

Eric - you are great at presenting things in an easy understandable way.

Eric: I made a living as a nuclear physicist, and had mostly mechanical profs that were useless explaining anything but small subsets of their profession (especially the ones coming form offshore universities (useless teats). Too bad guys like U weren't tutors at Engineering schools who have/had real practical knowledge and maybe from a societal viewpoint we wud have some of our youth migrating to the real world instead of playing video games. Thanx, Buddy as I say to my logger friends who help me down dead trees for firewood. Real men are sooo rare in US n canada.

lifetime gearhead, past mechanic and auto enthusiast here. This is probably the best explanation of torque converters I have ever seen. Nice job!

Well explain. I knew this but needed a recap. U nailed it. Thank u bro

Simply incredible work Eric , I've been watching your channel for years. I also have taken an automotive electrical diagnostic class at a community college. Your work has been a great stepping stone in my automotive understanding In the past 5 years

This was probably the most seamless explanation of an engineering concept I've encountered on youtube! Great job!

I appreciate your ability to explain and in detail so that even the least knowledgeable person can understand.

Eric, you are a born teach Sir. For the first time in my life, I now fully understand how this unit work. Thank you so much.

Very simple and clear explanation. Thanks!

This video gives a fairly easy to understand explanation of how the impeller, the turbine, and the stator all work together in a torque converter transmission. Good job!

This is the best explanation of how a torque converter works that I've seen. I'm still mystified by the workings of a transmission, but this really helped.

Thank you for giving clear information with no background noise and good lighting.

I used to have no idea how a torque converter worked, but after this video, I'm confused about fans too.

Eric thank you so much, you are a top notch Car Professor for all us to learn. You make it easy to understand even the most difficult things. Thank you teacher...

This explanation of stators was much better than any I've seen in engineering school.

Brilliant explanation with the two fans! This is exactly how a turbine shaft engine works on helicopters. The Compressor section and turbine section are only connected by hot air. The expanding gases force the power turbine section to turn and power is transferred to the main transmission.

Having been a motorcycle mechanic the last 20 years I have had very little knowledge in auto specific things. This is a great explanation of how this works and the potentials of issues. Thanks for the video.

Great tutorial! Back in the day Buick Dynaflows used the variable pitch torque converter you mentioned. Your concise explanations and demonstrations couldn't have been better. Crystal clear!

Great practical demonstration!

Bloody brilliant. Everything I wanted to know. And I was asking myself about stall speed when you explained it. Cheers.

I would have been an engineer if this video was uploaded 12 years ago. Very informative video. Liked it. Please keep uploading the great videos like this one.

This video should be used as a guide line for informational vids

I love the video I've never seen inside of a torque converter and understand fully how they worked you did that just like textbook classroom perfect thank you

Finally someone that speaks on my ability to relate and understand. Thanks. This was solid

Plenty of modern transmissions lock up the TCC in most gears, only unlocking to shift gears. It helps fuel efficiency and power delivery a lot.

Watching almost exactly 10 years later and finding it helpful.

I appreciate your presentation. This is a subject that I had never looked into before, so it was all brand new to me. Before now, the torque converter was that big thing under the bell housing, between the engine and the transmission. You gave very eye opening information on precisely what is going on inside the metal shell. Thank you.

A super great video. 10 days ago, I had to add transmission shudder fix because at shifting lower gears, I had hesitation till I built up to top speed and gear. Now I better understand why the shudder fix worked for me. Thanks for the great video.

Engineering at its finest.. Fascinating how someone could think of such complex components.. Eric, you did an excellent job explaining the converter.. Great job

I like the fan demo but the fluid passing through the stator is coming FROM the turbine and going BACK TO the impeller, not the other way around as you depict. The flow in the impeller goes in an in-to-out direction (it's getting spun out by centrifugal force) and enters the turbine at the outer edge. It flows from the outside to the inside in the turbine - it's called a 'radial inflow turbine' implying that the fluid travels radially inward - and exits closer to the centreline. Then it goes through the stator and back into the impeller where it gets spun out again.

Eric is awesome.

Eric, you're way of explaining things is amazing. You're a genius!!!

Eric, Thank You for giving some of us a great tutorial about lock-up converters. Now I have some back-up to explain to some who want to argue. Thanks again.

Fantastic video! I work at an auto salvage yard. I see those things all the time. All I knew about them is that 1. They are heavy 2. You think you got all the oil out.... BUT NOOOOOOO!! You didn't get all the oil out. 3. I'm tired of cleaning all the oil they spill. 4. I have always wandered how they worked and what was inside.

so I want to say that as a fellow mechanic and frequent you tube visitor i am highly impressed with your teaching skills and knowledge transfer processes and techniques. This is one of the coolest and more fun mechanical component explanations I have ever seen. I subbed and liked just now and I look forward to more from exploring your channel. Well done sir, this is truly well done and a gem of a mechanics video.

I have a 2004 Volvo S60R whose torque converter just failed. Thanks for demystifying this for me!

I was raised in a wrecking yard, changed many transmission, rebuilt a few. But never understood the torque converter,. This helps. Who figured this out, was a genius without a doubt. Thank you so much. I never even seen inside one. Till now, clearer but still a bit confusing. Thanks!!

Eric you always teach me something of great value on every video! Keep it up ! It was great the way u used fans for a simplified visual.

who came up with all of this to begin with?? holy cow this is amazing

One of the best explanations in RU-vid

I have been an armchair mechanic for a very long time yet none of my mechanic friends have ever been able to adequately answer my questions about that big donut. After watching your video, I now see why they were unable to convey the concept to this mere plumber. As it turns out.. I now (thanks to you) probably understand better than they what is going on inside. They knew when a torque corverter was bad and needed replacing.. which was almost never.. but they couldn't tell me why.. Thank you SO much for creating this informative as well as well illustraded instructional video.

Thanks for the demo. I had a rough idea how this device worked, now I have a more complete understanding. Also it is interesting to see other technologies combined to make this work. The starter motor clutch on Honda motorbikes comes to mind. Great video.

FIrst, I loved the " practical" with the fans -- it really demonstrates the concept. Second, some automatics designed for hauling heavier loads will use the lockup clutch in more than only the highest gear in order to limit heating of the transmission fluid.

i agree with @andypeak8151 i have been around a long time built many parts of cars and racing, and that was the best explanation of Torque Converter & I was even being taught years ago & learning transmission on a top team to be a trans guy, on a 5000hp Top Fuel Dragster. I never had anyone explain in such a way, simplistic and with fans, great video. amazing what goes into a torque converter. last few statements were a plus.i will be looking over all your videos now. love learning and miss my car days from off road racing to IMSA to NHRA You gave me a rush to go get a race car and build understand and race again ;') Thanks for rejuvinating a man that just turned 60. Maybe a GT3RS to learn and run now ;') LOL Thanks again ;')

Magnificent explanation and now I have a functional understanding of what's actually occurring - they are quite magnificent piece of engineering and so under appreciated

Brilliant explanation and an excellent practical analogy with the 2 fans. Great stuff!

Dude, awesome explanation. Huge thanks for the huge effort!! ...man, it is so crazy what engineers came up with, isn't it... X_X Greetings from Germany!

You could also explain that the the moment you touch the brakes, the clutch releases by cutting oil pressure to the clutch. You can actually see it happen. Next time you are driving up a hill and the clutch is locked, touch the brakes without releasing the gas pedal. You can see the RPMs rev up a little.

Eric, you increased - again! - my knowledge of automatic transmissions. Thank you.

That fan demo was genius , good job for explain this , thanks bro ;-)

Always wanted to know this.....good explanation.

Man I had a hard time figuring out how and what the stater does you did such a great job here even i get it now. Thanks!!!!

I'm glad to finally know the operations of the automagic transmission.

As I'm watching this video my wife says, "What about a Turkey Burger?" 😂😂💀

Excellent, thank you sir. Great explanation of the Torque Converter Clutch.

I had a "ah-HA!" Moment. Great video. Best 20 mins of my life

Great time to be alive and the technology to watch videos of the engineering that literally drives our lives. Great video with understandable teaching. Thank you.

You, Sir, are a Legend. Thank You!

this was great!! i absolutely appreciated someone finally explaining this well.. Thank you!!

You had me thinking pretty good explanation until you started to explain how the stator multiplied torque. Your explanation missed the mark. 1) the stator redirects fluid coming from the turbine as it reenters the impeller. Not the other way around as you stated. 2) The stator is not just for breakaway in fact the torque converter varies the torque that it multiplies over a large range of driving conditions during which time the stator is locked. 3) The stator doesn't start to free spin until the turbine is rotating at approximately 90% of the impleller rotational speed. 4) Your first statement about the stator OWC stating that it was a roller clutch but then you called it a sprag. Roller and Sprag One Way Clutches (OWC) perform the same task but accomplish it differently. One uses rollers and the other uses sprags. Stators always use roller OWC's. 5) Modern day vehicles can and do often start to pulse the TCC on as early as in 2nd gear. This would not be 100% engagement but partial engagement. Even my 94 Acura with a 4sp will 100% lock up the converter in 3rd gear. So the transmission does not have to be in high gear before the TCC will apply. Unfortunately I would not be able to recommend this video to my students for educational purpose with your stator & TCC explanation as is. If you want to be accurate I suggest you edit this video and re-post.

Dmn this guy explained this crystal clear

@ 7:25. I thought the flow was the other way around from the stator...The flow from the impeller to the turbine is from the outer radius of the impeller to the outer radius of the turbine...and then the fluid flows from the inner radius of the turbine, through the stator back into the impeller.

we should reimburse Eric for his two tutorial fans

This was without any doubt the best explanation of this I have heard. Thank you. I now wont gloss over on this subject.

While you're answering these sort of questions, maybe you could cover: Dark matter/dark energy The meaning of life Women thanks

im a manual guy here, but i've always wondered how auto transmissions work

The stator explanation completely lost me. After some further research, I found that the explanation was inaccurate. The stator alters direction of the centre return flow from the turbine, not the outward flow from the impeller. Because of the way the turbine blades are made up, the return flow from the turbine is opposite from the direction of the impeller rotation and that would oppose impeller rotation. The stator comes in and redirects the fluid flow to match the direction of the impeller blades. The torque multiplication occurs when the force of the fluid hits the impeller blades in such a way that it assists with engine rotation. The stator starts rotating when the impeller and turbine start approaching the same speed. Hope this helps anyone else who also got lost.

Dude! The fan analogy was genius! That’s the first video I saw that actually brought me close to understand how the torque converter works

So that is one of the reasons you feel a "boost" off the line when you press both gas and brake at the same time in an automatic vehicle, and then let off the brake... Your engine is at the stall speed, so the stator is multiplying torque, but the brakes are holding the vehicle steady. Release brake and feel the full power of that torque, but once moving the stator is no longer multiplying torque and you realize that your 97 camry actually does not have as much power as you wished it had XD (Right?)

for not having a program or CGI to help u show what ur talking about. u did a great job explaining how a torque converter works. showed me something i didnt know. but wanted to know. thank u for ur time in making this video.

I think the take away from this video is the understanding why the repair of an automatic transmission is so much.