AWD Cars - All Wheel Drive - Explained

[@_spooT]

we need more people like these in schools. Most teachers/professors just follow the book to the dot and then students become like brain-dead robots. When you could put more effort in it, understand the book yourself, and explain it to the students in a much more simpler and effective manner. I appreciate people like these man

[@EngineeringExplained]

My next car will likely be an STI actually, so I guess that answers your question. I love hatchbacks, I think the STI sedan looks boring. From a performance basis, the EVO can probably put down better track times, but it's not hatch and loses so much practicality. Also, the next gen STI is supposedly going to shed some weight, and possibly come in 2 door. I'm a big fan of 2 doors.

[@DTechnologyservices]

Why even read a dam book when you got intelligent people like this to spoil the fun on youtube!!! thanks so much great work!!!

[@EngineeringExplained]

Well it depends on throttle position, but to answer your question in a simple manner, yes. You put a constant A/F ratio, but that doesn't mean that the amount of air that comes in is constant. Increase the amount of air (by designing for optimum flow, or adding forced induction) and you must then increase the amount of fuel burned.

[@EngineeringExplained]

Oh I don't know. It's all about the application, they all work. But do you want full engagement (good for off-road) or do you want to allow slip (great for on road)? Or do you want partial slip with torque transfer (viscous coupling)? All just depends really, they each have a purpose for sure.

[@EngineeringExplained]

If you haven't watched my video on transfer cases that's a great resource to check out. After that I'd look to any documents relating to your vehicle, to see what the actual set-up is. Glad you like the videos!

[@EngineeringExplained]

It allows for some difference in speed between the front and back. When the speed of one exceeds the speed of another it transfers torque, but this does require a difference in speed, which makes cornering on pavement doable. Kinda the same principle as a torque converter, when you step on the gas, your engine is spinning faster than your transmission, but they are linked.

[@EngineeringExplained]

Well, it's symmetrical. Unlike the one I have shown, the transmission is placed longitudinally, so all of the components are balanced as far as weight. And a viscous coupling is used to transfer torque to the tires with more grip.

[@normaspirated]

Honda's full time sh-awd uses multi electromagnetic clutch packs that are integrated into the rear differential. When taking a fast turn, the clutches that are associated with the rear outside wheel tighten up. This inevitably causes 100% of the torque/power to transfer to that one rear wheel, and no power to any of the other 3 wheels. Kind of causes a "peg leg" or row boat effect (rowing outside oar only). Pretty cool and sophisticated system.

[@EngineeringExplained]

Some sort of differential yes, you wouldn't want a locked mechanism that wouldn't allow for separate speeds. I was just saying it's possible to have a direct drive.

[@EngineeringExplained]

Yes, you could see gains by reducing the amount of driving wheels. It is better in that all of the weight of the car is on the driving wheels, so you can accelerate quicker if you are traction limited without AWD.

[@EngineeringExplained]

Yes, the back would get 5 lbft UNTIL the viscous coupling/locked diff began to spin. If the differential was locked, and the front tires are spinning, that would mean the rear tires are also spinning; so you'd either be moving, or burning all four tires.

[@EngineeringExplained]

I guess it would still depend on how much power they have, how much grip, and where the weight is located. AWD will allow for a faster start, but it means more losses from the engine, so it could still lose over a 1/4 mile if they all have the same engine. RWD could be second after AWD, as weight transfers to the back upon acceleration, meaning it could put down more power, but FWD typically has the least amount of drivetrain loss. Any of them could win depending on differing characteristics.

[@EngineeringExplained]

One can be placed near the bevel gears at the front. I did this for simplicity so it would be easy to understand power going to front and back.

[@EngineeringExplained]

Power is created by turning the chemical energy of gasoline into heat, and using that heat to create mechanical energy. If you want more power, you must burn more fuel. Or you can improve the efficiency of the engine/driveline/reduce rotational masses, but ultimately it comes down to more fuel.

[@chrisharrel8837]

I would love to see a video where you discuss AWD vs FWD in terms of traction and safety to help decide if it's actually worth the additional cost when purchasing a vehicle.

[@EngineeringExplained]

Power would transfer through any 3 (or combination of any) of the center items, whether it be a clutch pack, center diff, or viscous coupling.

[@EngineeringExplained]

Depends on the center diff of the 4WD vehicle. If it's locked, then the 4WD vehicle has the advantage, if it's open, then the AWD vehicle has the advantage, and if it's an LSD then they are about equal.

[@EngineeringExplained]

Some sort of coupling, yes. Though I suppose it would be possible to eliminate one if it was driven directly from the transmission.

[@EngineeringExplained]

Yes, but it's purpose is to get them to rotate at close speeds, to eliminate the disadvantage of an open differential (one set of tires spinning, the others stationary).

[@EngineeringExplained]

Well, for one it's actually symmetrical, as in when you look at it from above the vehicle, shafts and diffs and the whole system is basically mirrored if you cut the vehicle in half. I don't believe this is very common, most are offset one way or another.

[@EngineeringExplained]

Yes, in principle.

[@EngineeringExplained]

I'm fairly sure power is always split on the GTR, there's never a time when it's just sent to one axle.

[@coleman6131]

Very helpful, thanks! BTW, what's that thing on your head?

[@EngineeringExplained]

Yes, at the connection of the transmission and the front drivetrain.

[@EngineeringExplained]

Well yes, AWD vehicles have more frictional losses than 2WD vehicles, but also Evo's have powerful engines so they consume a lot of fuel.

[@Mr.Exquisite]

Hey Jason, the way you figure a mid differential is incorrect. A diff is always driven on the outer ring (those 2 gears you connected to nothing are actually sitting on a ring) and outputs torque on both left and right, or in this case, front and rear. You cannot just put in a diff anywhere in the axle, it has to be where front, rear and driven axle meet.

[@EngineeringExplained]

It's very true. Thank you!

[@michaelpacman]

I thought the Honda CRV is 4WD because it has a transfer case?

[@asdf8391]

just wanted to point out what i believe was said incorrectly. The differential serves to allow left (or right wheels) to spin faster or slower than there counterpart when navigating a turn. This is necessary to prevent slippage of the inner tire, as it will not travel as large of an arc as the outer tire. In the video it said front and back wheels spin differently. Let me know if I'm wrong. Thanks for the video!

[@tesznye6992]

The front and rear wheels also have to spin differently. It's the same as you'd find on a front/rear axle, only it's not the 2 side wheels connected to it, but the front and rear driveshafts

[@JoeJ-8282]

Yeah, this drawing of this kind of setup would ONLY apply to the FWD biased "auto" 4WD systems that use either the viscous coupling or the electronic clutch pack to send power to the rear, but NOT to the one with a center differential, because if you have a center differential, (whether with or without an attached viscous coupling, which only makes it a limited slip diff.), then in that case your drawing would have to be changed completely, because in order for a diff to work properly you have to feed the diff. first from the transmission, (and not the front wheels directly), and then and only then, the torque would transfer through the front and rear outputs of the diff to the respective front and rear diffs and axles... As in how Subaru and a few other of the more "symmetrical AWD" systems work... You should make another video explaining this major difference between the two major types of systems, (i.e. FWD biased like this and ones with a center diff)!

[@lfgamble3924]

The diff would be on the front axle. I assume he just moved the diff back to make the drawing more clear

[@lfgamble3924]

I see what ur saying tho. Cuz some awd vehicles have diff in the center of the drive shaft. I did NOT know that. Cool

[@johnstrickland6230]

Yeah this explanation isn't bad, but it does only seem to illustrate the honda civic wagon and honda crv awd systems. To be fair though as many different setups as auto manufacturers have come up with you'd have to make quite a lengthy video to cover everything.

[@luizbruno2010]

do you know why in this setup a rear diferential with a gear reatio is used? because apparently it receives traction from the front wheels after passing thru the front diferential

[@willdriverc]

I was just watching a video from Borgwarner about Haldex systems. The central differential that some Audi's use. It might be worth doong a video on this system. It is a pretty cool setup and this one uses a centrifugal lever system.

[@ZAZAP]

buddy Im literally on the cusp of purchasing a very capable crossover, you really helped clear up my confusion!

[@yogertdog]

ZAZAP dont get a cross over get a turbo diesel truck. youll thank me later...

[@infokemp]

Slightly tangential subject - if you have a viscous coupling - if the unit is punctured either by striking a rock etc on the road or in military terms a mine or IED punching through the armored belly of the viscous coupling unit - can you have a viscous fluid (as in self sealing fuel tanks) that self seals itself on contact with air - to give a sort of TV science example the same way as custard creates a solid skin or is able to temporarily act like a solid when absorbing energy?

[@ship_wreck_d3349]

A great way to demonstrate how a viscous clutch works in your own home is to take an egg (a raw egg), and spin it on your counter top, grab it and stop it and immediately let go, it will continue to rotate due to the inertia of the viscous fluid (yoke) inside exerting friction on the shell, without any outside torque applied. If you were to apply external torque, there's a viscous clutch.

[@killerstang71]

like a young professor demystifying automotive topics - thanks bruh!

[@oldfashionedwrx3574]

DCCD (Drivers Center Controlled Differential) are good, you can use them off road, on corners by powering more power to rear wheels and then as you exit power more power to the front to exit, also 50:50 split for rain would be good, 70:30 for a good launch in racing, I want an awd car that does this like a wrx sti or something.

[@WillPittenger]

I should add one more "AWD" system. For the past 15 years or so, full-size GM pickups and SUVs have used a part-time system with push button controls. If you were to examine those buttons, one would be labelled "AUTO". Auto mode is RWD unless the computer spots slippage. The vehicle, for the most part, could probably be left in Auto unless you need LO (which is present) or you're low on fuel.

[@mezodani]

Dude, YOU are fantastic! I love your videos, I wish there was something similar when I was studying engineering..

[@arcticwolf6019]

Is a transfer case an integral component of any AWD set up? If so, why is it not part of this vid? Besides, if the Bevel gear is always there, doesn't that mean that torque will always be transferred to the middle shaft regardless of the AWD type? How can a viscous coupling grant a 50% transfer of torque when fluid is included? Too many questions. I have to admit, I'm starting to get a little confused since the 4WD vid. Maybe I'm rushing things. However, I can never thank you enough for such great explanation; it is the reason I'm eager for more knowledge about automotive technology now. Thank you, Jason!

[@fiskusmati]

Why there aren't avaliable any cars (wagons or sedans) equipped with 3 locking differentials? Yes, subaru has nice awd drivetrain, but I wonder that subaru legacy has 3 locking diffs - that would help them in off-road situations.

[@bogaravila8060]

Can you make a video explaining how having different tire compounds from 2 different manufacturers could affect the reliability of the AWD system

[@oldfashionedwrx3574]

2wd utes have the 4H/4L settings 4L for max torque for hill climbing, 4H for low traction (but manual says not to use it much.) 2wd (rwd) for normal driving. (source: personal experience) awd like on a subaru is full time depending on the model forester gt which I have I believe is 50:50 for performance models like the wrx sti it is 41/59 then chances on corners, the situations I think. fill me in if you know the gaps :P

[@EngineeringExplained]

Didn't know they made AWD G35's. That's awesome!

[@EngineeringExplained]

Of some sort, pretty much yeah.

[@rickbingwakk1982]

Greatly experienced and well explained thx.

[@EngineeringExplained]

You certainly could, but you're adding weight and complexity with each.

[@simr2105]

Two important points: Your diagram shows the centre differential having its input coming from the front differential. The input to the centre differential should be from the output of the gearbox. There should then be TWO outputs from the centre differential: one to the front differential and one to the rear differential. AWD vs 4WD is a vague marketing term about the style of vehicle (heavy or light duty offroad), not the drivetrain itself. My 'AWD' Forester has high and low range.

[@davidrestrepo3721]

I understand how differentials work when it comes to splitting the power between two wheels but I don't understand what the center differential in your drawing is doing. :/

[@JoeJ-8282]

Yeah, he has it drawn wrong for a differential based system... This drawing really only applies to the FWD biased systems that use either a viscous coupling or an electronic clutch pack to send power to the rear... A center diff would have to be fed engine/trans. power first, and then from that it would go out to the front and rear, and in that case, the front would *not* be fed directly first, as he has it shown here!

[@kathygrill1702]

@@JoeJ-8282 he is describing the 3 main different types of AWD systems. He just simply drew it all on one picture and described each individually. He clearly explains that they are completely separate systems and that they are all not on any vehicle.

[@kapitzkes]

I believe the viscous coupling produces a 50/50 split in normal operating conditions. I could be wrong, but in my car (with viscous couplings F + R) it "feels" AWD... all the time.

[@lfgamble3924]

Pretty in depth. I liked it.

[@crewtheaftermath4105]

great job. helped me whiddle downmy winter tire choice. thnk you!

[@EngineeringExplained]

Yep, pretty much the same idea.

[@thabg007]

yea and it works great in the snow, im the one that wrote on ur facebook wall requesting 4wd/awd explained lol

[@CRVB7]

Can you explain different AWD systems used by different companies on sport cars or even exotics(aventador,R35)? How they manage to get a better acceleration since power is limited by traction?

[@teapot55]

Hey, just to have a better understanding. What is crown gear center differential and how is that related to all of this such as transfer case. Im wondering because I saw a video simulation of the New Audi Quattro and was wondering if that is also what you are explaining.

[@prandomable]

one question, how is an AWD vehicle with viscous coupling (w/o center diff) makes the front and rear wheels to rotate at different speed when turning?

[@infokemp]

@EngineeringExplained So is this system very good for Recreational off-road or military wheeled AFV's? Great videos. Learning a lot.

[@jacewanca4240]

Best vid I’m trying to make an awd go kart and this helped a lot cause I’ve been looking for a vid like this

[@Gred079]

I've got a more of a personal question. The Ultimate rally cars question. Wich do yo prefer subaru wrx/ wrx sti or the evo.. and more importantly why? what are the differences since as far as i know theyre both 4wd, 2lt, 4 cyl, turbocharged engines.

[@Digidi4]

viscous coupling is in the second generation toyota rav4 but I don't know about the axle differentials on it

[@oldfashionedwrx3574]

it is because the way it is configured I googled it "longitudinally mounted horizontally opposed engine awd" the boxer engine is like a rwd engine because it isn't side ways, perfect for a drive shaft to be slammed down it. even coventional engines with rwd configuration are off set. just google subaru awd and first row of pictures should be a photo of it vs the rest. just google subaru awd and look at the pictures.

[@noxth]

Do you have a clip explaining all wheel drive of mid engine car like a lambo? thank you for such a great vid!

[@Denstoradiskmaskinen]

My car is a standard, it has front engine with FWD, but since it was made in different models, it still has higher floor in the middle.. possible shaft placement? Could i install a shaft & viscous coupling, or should i not bother, old Volvo V50.. can probably just buy another with AWD.. but since there is a tunnel.. ? :)

[@EDXR61993]

What about Subaru Forester Duel range models we have here in Australia. They have a low range leaver but are by subaru's own terms AWD.

[@TexHasselhoff]

I would like to make my 4x4 1984 Sierra AWD. Would a viscous coupling and new driveshaft for the front axle meet the requirements or would more have to be done? Note the truck is for mostly road use.

[@yogertdog]

Xboxdip60 you could replace the transfer case with another diff...

[@anejonjukema2409]

Would you make a video about the diffrences between quattro and 4 motion?

[@elwulfo666]

It's the same. Passat, Golf, A1, A3, Tiguan, Q3 and some others use this type of All Whel Drive. Cars like the Q5, Q7, A4 and so on, Macan, Cayenne, Phaeton, Touareg and in fact any VAG car with a longitudinal front engine have an LSD as the center differential.

[@swapnilkardile1]

Plz explain 4wd system in 2017 hyundai tucson 2.0 disel which comes with centre differential lock. Hyundai calls it intellimatic 4wd system. Pls explain how does it works. And is that system helpful on road as well as off the road ? Plz reply🙏

[@snowlover71]

I'm so glad that I found you.

[@laimunwai]

Hi , Can you explain which one got the fastest acceleration comparing with fwd, awd, and rwd with the same engine output? Thankss

[@EngineeringExplained]

Lai Mun Wai AWD would have the best launch, but the most losses. RWD would probably do the best, as weigh transfers to the rear. FWD would likely have the least amount of power losses.

[@JuanMorales-jg3oi]

Hey man, just starting to get into cars and I want to enhance my mechanic skills. Whats some good tips for a beginner? How should I start.

[@hypedbros8329]

I have a question, does the placement of the differential determine power output? For example I have seen rear wheel biased systems, and when I see the front differential it is usually on one side. Does the side that is closer to the front differential get more power

[@newtonbaba177]

not related to the video but can sombody explain the relation between catalytic converter and fuel economy of car? whether there is any effect of its removal on fuel economy? car has two o2 sensors pre and post CC. thanks

[@MotorCitySteeler]

This good sir is going places👍Thank you for the informative video✌

[@agt155]

The difference between 4WD and AWD has nothing to do with hi-lo gears. It's just Hi-Lo gears usually indicate a mecahinical 'link' between front and rear axles that defines '4WD'. AWD drive systems usually use some sort of viscous coupling to transmit torque between the axles.

[@Ma4onka]

ok i liked the video but i have a question for you if you can send it to me. Manual vs Auto if you can explain to me the pros and cons of both will be super. Tnx for the dreat vids

[@cwj9202]

How about using snow chains on the rear axle - would that cause problems?

[@Fgvale001]

Awesome explanation. Easy to follow. Thanks.

[@EngineeringExplained]

You're welcome! Thanks for watching!

[@SomeBodiess]

Engineering Explained Where did you learn all this stuff about cars? Its crazy how much for being so young Haha Great Vid Btw

[@joefisk4448]

So with the viscous coupling the rear tires are only powered when the front starts to spin (slip)?

[@WeBleedGreen1]

I'm sorry but I have to say I disagree. You can have hi/lo in an AWD application. My '99 Grand Cherokee Limited had AWD with hi/lo and neutral, but no 2wd. all my truck and other jeeps have been 4wd that have 2 hi, 4 hi, Neutral, and 4 lo, (the jeeps have part time/full time 4wd, and the trucks technically have 2lo if you leave the front hubs unlocked)

[@lfgamble3924]

U have that because those also have 4wd.. if it was just awd without fwd. U wouldnt.

[@lfgamble3924]

4wd*

[@afterburnerbg]

Can you explain why car companies claim that automatic awd makes cars more fuel efficient? You still spin all the axles, rear diff, propshaft, so the frictional and rotational mass losses would still be there.

[@Dake21]

There's also AWD (full time 4 wheel drive) trucks with lockable center diff and low range.

[@EngineeringExplained]

David Cazes Yep, check out my video "transfer case - explained."

[@EquityDevelopment]

I have an 2007 hummer h2 and it is all wheel drive all the time. How can I make it be just 2 wheel drive when I want it to be? My old jeep Cherokee could switch back and forth. What needs to be changed in the hummer. Thanks for the help.

[@matty0234]

buy a different truck. problem solved.

[@philstat100]

Let me ask You, Does 2001 jeep grand cherokee have those sped sensors in the front wheels? Again Thank You

[@solarchild741]

You are a great educator!

[@thetopgunngroup1798]

Question: Can a 2011 Mitz Endeavor awd be towed either with a tow bar or tow dolly, not a trailer, by disconnection the rear driveshaft or something? It has traction control/

[@P3aceMaker94]

hi there, in the auto awd situation would having the continuously spinning shaft spinning the clutch to rear axle increase rotating mass and detract from whp?

[@abelbarcenas8249]

Dude you are really good at explaining this :-)

[@yzqpc]

The graph seems wrong to me. The open central differential should be different from the wheel differential located on the wheel shaft, right? because one has got 2 rod connected and the other one has got 3 rod connected. If the central differential is like the one you draw, then the two shafts connected to them will rotate in opposite direction and no rotational difference will be allowed.

[@wwonka52]

i just acquired a 2013 Nissan Juke "S" model that is 2wd, unless i push the button on dash for AWD. Never used AWD yet, just plan to use Awd for snow. Right?

[@EngineeringExplained]

That could work, yes.

[@7150285]

i didn't know there could be a center differential for AWD system... and btw, how's subaru symmetrical AWD system different from others?

[@yzqpc]

It seems that the viscous coupling will only engage when there is spining in the frong wheel. So under normal condition when it's not spinning, the rear wheels do not receive any torque just like 2wd. Apart from the reaction time, the condition under which it will engage is very similar to that with a multiplate clutch. In the case of open differential, the rear wheel receive torque if the front wheel is not spinning, and does not receive torque when the front wheel is spinning. Confused!

[@teletech111]

What AWD system does my 2005 Saturn Vue have? Viscous I assume because I seen no wires connected to the Rear Drive Module.

[@7150285]

so in general whether's it FWD, RWD, AWD, part/full time 4WD (will) always have differential right?

[@joonyaboy]

How does the ECU engage the multi-plate clutch? A solenoid?

[@segurosramongomez]

subie owner first view!

[@SwaggyT91]

how can the open diff split power to the front and back. using your example if the front wheels were on ice and can only transmit 5 lbft of tq to the ground than the back wheels will only get 5 lbft of tq, and you're going to be stuck even if the multi plate diff or viscous coupling is locked up right ??

[@prandomable]

so viscous coupling can allows the front and rear tires to rotate at different speed correct?

[@greatwhitejake88]

Nummy, they have whats called limited slip differentials. Which alliw the wheels to spin free to the opposite side engaged. And tim it works the same way whether or not its constant front or rear wheel drive. The computer will comensate for traction loss and put the power where it needs to go. It works the exact same way

[@brandoGTR48]

Does the regular (non-automatic) AWD have the multi-plate clutch or is that just for the automatic AWD?