Viscous Limited Slip Differential - Explained

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How do viscous limited slip differentials work? Viscous limited slip differentials use a viscous coupling that allows for torque to transfer to the wheel with more grip. It is an alternative method to a clutch pack differential, though by design it is not as effective at locking the two driveshafts.
NOTE: Regarding the annotation at 2:30. I misspoke here. What happens is the right driveshaft and differential housing will both be rotating. Because the pinion gears are also rotating (green gears) around the left driveshaft gear, the right driveshaft gear will have to rotate faster than the differential housing. So, the right side of the diff will be attempting to decelerate the right driveshaft (or accelerate the diff housing) once it breaks free, while simultaneously the left side will try to accelerate the left driveshaft. Because of this, it is possible to just use a single viscous coupling on one of the driveshafts.
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15 янв 2013

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Комментарии : 176

@tafaragadze6432 2 месяца назад

Years later and I'm still using these videos.

@TheKoenBrouwer 9 лет назад

Mate you're safing my education. Without vids like this I'lld be staring blind at these illustrations in my book. These explanations of yours help me understand everything way faster and better. Thank you!

@EngineeringExplained 11 лет назад

I have multiple videos covering this, I'd recommend starting at the beginning of the "differentials" playlist. Locked diff means both wheels always rotate at the same speed; torque distribution can vary.

@AWDfreak 11 лет назад

I'm glad to see so many of these LSD explanation videos. It really does help other people to understand why most road-going cars with open-differentials aren't as effective under low-traction situations.

@EngineeringExplained 11 лет назад

Glad to have you on-board, thanks!

@DonTruman 4 года назад

Sounds like a great idea. Simple, durable, and somewhat effective for getting out of a slippery spot.

@EngineeringExplained 11 лет назад

Thanks for watching, don't know much about infinitis AWD system, but I do wish they'd put it on the coupe version; that'd be an awesome car (as an option). Probably just fine.

@NicMagz 7 лет назад

I'm not entirely sure why, but the phrase "a pile of ice" literally made me laugh out loud. You just made my day, good sir.

@erinmills6610 7 лет назад

Or just some ice.

@ryanmalin 4 года назад

this comment is depressing

@EngineeringExplained 11 лет назад

Different methods, there's likely a cost difference as well. A VLSD will act a little more like an open diff than a clutch type, as it will allow for varying speeds before creating a restrictive force to get the diff close to locked. A clutch type could be locked in situations like cornering (while accelerating) where you may not necessarily want it locked. But ultimately, there are numerous solutions to every problem.

@EngineeringExplained 11 лет назад

Haha appreciate the comment. I try to make multiple at a time and then take little breaks. Helps me keep up with the "video every Wednesday" idea.

@EngineeringExplained 11 лет назад

No, torsen uses a system of worm gears. I'll have a video up soon enough!

@EngineeringExplained 11 лет назад

Some have center viscous couplings splitting power from front to rear, yes. Not sure which makes and models, but most companies will say on their websites. LSDs cost extra money, so they're worth bringing up to the customer.

@wangyue9754 7 лет назад

Great video! Clearly explained the idea. Seems VSLD will result into some understeer when cornering, especially for sharp turn.

@mitoand9 6 лет назад

I think there is one important point to add in these video: viscous LSDs cause understeer by nature during steady-state cornering (outer wheel is forced to slow down and inner wheel is forced to speed up due to the increase of viscosity of the fluid). This is something that should be stated in my opinion when talking about clutch plate and viscous LSDs, since the transient vs steady-state operation of a vehicle during cornering is not the same.

@EngineeringExplained 11 лет назад

Great point, thanks for sharing.

@sTeadFasT96 11 лет назад

Very great video and awesome educational resource. Keep doing what you're doing! You have my support.

@TheOhsemix 11 лет назад

Thanks for the vids...and dont forget to take breakes if it gets stressing trying to make them its good to get off time

@angelalevitan8399 Год назад

Wow great video. I love all of your videos and you did this a while ago. You look so young in this video

@EngineeringExplained 11 лет назад

Thanks for watching!

@EngineeringExplained 11 лет назад

Yes, it's possible. I'm not sure how long the fluid lasts before needing replacement. I'd assume it'd be a long time; it's sealed, and there's not really any source of contamination. The only thing that happens to it is that it heats up and cools down.

@EngineeringExplained 11 лет назад

Such a dedicated subscriber, thanks haha

@EngineeringExplained 11 лет назад

You're welcome!

@vkotis 8 лет назад

I finally know how a vlsd works..Thank you!

@padraiggalvin2807 9 лет назад

Great videos, very well explained

@EngineeringExplained 11 лет назад

In principle, yes.

@dannyradomski7041 11 лет назад

The liquid in the housing is typically a silicone based fluid, so when the plates move at different speeds, the sheer forces make the fluid turn more viscous. This helps to lock up the diff.

@TheAefril 6 лет назад

+1, Explained perfectly 👍, Thank you.

@EngineeringExplained 11 лет назад

Perhaps, or a liquid that changes viscosity very quickly once the two shafts rotate at differing speeds. A clutch type LSD may be a better option.

@EngineeringExplained 11 лет назад

Not sure if you're saying while driving or if you just have the car lifted and spin on tire. If it's the latter that you're doing, it likely works, but the speed that you rotate the wheel isn't great enough for the liquid coupling to rotate the other tire.

@Brancalbin 2 года назад

This video brings memories

@Nike10Soccer787 11 лет назад

love the explanations!

@EngineeringExplained 10 лет назад

Well VLSD does not act instantaneously, where as clutch/torsen diffs do. So if you want maximum torque transfer (instantaneously) to the wheel that has the most grip, a clutch type or Torsen (if both wheels maintain contact with the ground) are your best bet. Viscous is fine though, can do the job.

@turboluvr5404 11 лет назад

Don't want to confuse anyone, but during differentiation both viscous clutch packs are seeing relative rotation, and therefore are contributing to the torque transfer to the high traction wheel. Also, viscous diffs are what is called "Speed-sensing". They transfer torque due to a difference in the relative speed of the rear wheels, as opposed to "Torque-sensing" differentials that progressively "bind up" as they are put under more and more torque.

@ark-mark1 3 года назад

In RC the pinnion gears and pinnion axle are slowed down with the visco liquid making them turning more with the casing. The Casing is filled with the liquid and stiffer the liquid less it lets the side gears to turn separately. So stiffer the liquid, more "lock".

@EngineeringExplained 11 лет назад

Somewhat similar in principle, but torque converters use transmission fluid, which I do not believe changes it's viscosity characteristics much with temperature change; at least not to the degree that VLSDs do.

@nikhilkash92 11 лет назад

really nice videos!! keep them coming!!

@350Zquicksilver 11 лет назад

nice video young man... my 350Z is fitted with a (OEM) VLSD, makes a world of difference compared to an open diff... i've had both.

@danielvought5935 9 лет назад

youre the best man. thanks

@damiangorski6347 8 лет назад

explained perfect

@EngineeringExplained 11 лет назад

As the fluid heats up (via friction) the viscosity increases, thus causing the two axles to "lock" together.

@Cape1984 2 года назад

How is possible the liquid inside to increase its viscosity when is heated up? Should not decrease??

@EngineeringExplained 11 лет назад

Interesting, I would think that they should both spin together (similar speed) if you had it up in the air. Certainly the liquid shouldn't allow for much of a speed difference.

@genieohnehirnspaziern3819 7 лет назад

One question, just for my understanding: imagine a viscous-coupling used as longitudinal centerdiff. There is silicon oil (e.g. 90%) and air inside, not mixed. In operation with different speed the oil transfers torque, but the rotating plates also start to mix oil and air, so viscosity decreases, less torque is transmitted up to a certain point (hump). During normal operation (no hump) with higher speed difference more and more air bulbs will "hide" in the special shaped blades so that more torque can be transmitted? I always thought that viscosity of silicon oil increases but read somewhere that this oil is not dilatant...

@EngineeringExplained 11 лет назад

Similar to a torque converter in principle, yes.

@JohnSmith-hy1ir 3 года назад

Also quite similar in principle to a Tesla turbine (boundary layer friction between discs)

@TucsonDude 8 лет назад

Can't these VSLDs leak internally?

@tinkerbell69714 11 лет назад

Love your videos ;). Thanks

@FedericoLucchi 8 лет назад

Actually, the wheel on ice will spin twice as fast as the differential housing if the other wheel doesn't move, so the viscous fluid will both slow down the slipping wheel and accelerate the other one! ;) I love your work, keep it up!!

@billmunro3533 2 года назад

Good explanation in general, though I'm not sure if the late Robin Price, who did so much work on VC diffs, LSDs and viscous transmissions for FF Developments (And who I interviewed at great length for my book on Ferguson Formula 4WD) would agree that the plates are 'essentially a multi-plate clutch' as they do not touch unless something goes wrong

@emmanuelarthur1263 9 лет назад

hi, i was wondering how can this mechanism allow the ties to spin with different velocity in a curve, since the viscous flow may be acting anyway. How can this viscous differential act like an open differential when needed?

@EngineeringExplained 11 лет назад

Probably due to the negative characteristics when the oil heats up, as far as lubrication purposes. Dunno.

@jchoops7yt 11 лет назад

Super helpful video. Thank you. Is the fluid in the diff such that its viscosity increases with friction? Or, perhaps that it counter intuitively becomes more viscous with an increase in (friction induced) heat? My other idea is that it is similar to the fact that when I move my arm slowly under water I feel little resistance, but when I move it quickly under water I feel a lot of resistance. [continued in next comment]

@oldfashionedwrx3574 11 лет назад

just checked the rally cars the evolution and the STi, they both have LSD's, and the lesser model the plain WRX has open diffs. interesting that it states if the hand brake is used it does something to prevent damage to the VC

@fred16773 10 лет назад

Great explanation.

@heartkiller93 8 лет назад

it seems like a fraction of the power would be wasted with a system like this because neither side is ever directly connected, the diff housing plates would always be sliding through the liquid slightly faster than the plates connected to the axle receiving power from the liquid. am i right?

@jhalkoski 10 лет назад

to complete the differential series, you should make a video comparing Viscous vs clutch type LSD, which one is better in which applications.

@Grno1984 7 лет назад

Hi, can you tell me, my 2005 Subaru forester has rear VLSD, but it dos not lock up anymore, can i change the liquid inside the viscous coupling ? and what kind of silicon oil i should use and what viscosity?

@zees5888 6 лет назад

Hey im not sure if u could answer my question but i git a 2000 volvo s80 t6 with a viscous clutch and im not sure if i really need it. And if i just can reinstall a new cv axle but without the viscous clutch and if the car would preform fine

@thesetruths1404 5 месяцев назад

Hey man thanks. I bought my teen son a 2004 Impreza Outback 5-speed, 156,000 miles. AWD of course. We didn't notice a whine noise, but it just started clicking or tapping around curves and acceleration. I can feel the tapping in the gear shift handle. And it seems it sometimes loses AWD grip when it taps. So I think the center diff is binding the output shafts sometimes. Is this the noise that they make when the vicous diff is broken?

@EngineeringExplained 10 лет назад

The one in it is probably fine, they likely did their math to make sure it not only reacts quickly but holds up over time.

@asianwithoutasianeye 11 лет назад

really detailed thanks. what is a locked diff?

@bypreparador5683 11 месяцев назад

In finality of liquid is proporcity of generaty the atrict forçe from the plates and realises the proximity locking differentials, and not ghe principy of in fuction of flux ghe liquid corretly?

@tonyspark1071 7 лет назад

Really no one else was confused about the drive shaft vs axle? his drive shaft should be labeled what connects to the pinion right? and the " driveshafts " are the cv shafts. right?

@TameToothSGA 2 года назад

correct me if i’m wrong (because i want to understand better) but it sounds like it works very somewhat similarly to a torque converter. sending torque to the tires using fluid

@EngineeringExplained 11 лет назад

Check out my video on gearing "car gears" and "first gear torque." This should help you start. Just multiply across the gear ratios. :)

@michaelparker4830 7 лет назад

explain how the bmw m Visco Lok differential works fitted to.the E46 E90 E60 M SERIES

@silentbob9797 11 лет назад

Great Vid! I have a question: I have a viscous rear diff on my awd 3000gt vr4. With the car in the air, I spin one rear tire and the opposite wheel should turn the same way, but it doesnt spin at all. Does this mean my rear diff is not working? thanks!

@vignesh410 10 лет назад

What kind of differential can i use if i use Motor cycle engine and chain drive to transmit power to rear wheels

@nicholasxuu 11 лет назад

Like your videos. Just wondering why not just put the oil/grease inside the diff gear area? both lubricating the diff gears, and creating the VLSD effect. is that because those gears are so heavy duty they need special lubrication to work. so those oil need to be used with the clutches?

@mohamedidris9086 11 лет назад

hey could explain about roll center...........i hope that will your next video

@jchoops7yt 11 лет назад

[Cont. from below] Is it true that as the difference in velocity between the two wheels increases, the friction in the diff increases causing it to allow less slip? One final related question: Is a viscus LSD's utilization of fluid similar to that of a torque converter? Thanks so much for helping out!

@brotang2953 6 лет назад

i have a vlsd from a Nissan gti in my p10 primera ( g20 in u.s I think ) I've noticed some left to right shimmy on hard acc on gravel. left right left then both. to my understanding the vlsd essentially robs power from the spinning axle and transfers it to the stationary side. I cannot figure out how its flicking from side to side though??? any ideas.....anyone? its not a concern for me but be good to know what the hell is going on!

@Cambo866 11 лет назад

Is this similar to a fluid coupling for say a conveyor belt drive? I need to understand this for a mechanical engineering assignment. My understanding is as the motor starts up the power gets transferred gradually to the rest of the system. Is this correct?

@slickstretch6391 2 года назад

Can you change the amount of slip by changing the viscosity of the fluid?

@niklasxl 11 лет назад

so do you have different oils in the middle and between the plates with diffrent wiscosity?

@Brenby 11 лет назад

Will you do De Dion suspension in the future?

@derekmatthew6383 2 года назад

Hey do they make a magnetic limited slip differential? I feel that would be one of the easiest ways to make one and it would last forever.

@ortiz73ca 10 лет назад

What type of LSD is better for canyon driving and take off's from a light? I don't drift so that is not a concern. I have a VLSD but not sure what type is better.

@genmaxpain 10 лет назад

you need a video with cone type lsd's

@taddyvinda 9 лет назад

Just pointing out its not the same speed... The weel with less friction gonna spin faster than the diff housing around 1:2 ratio... Causing the viscus liquid to resist the movement as well as the weel with less grip to move with the housing. both of the friction surfaces to work simultaneously. But i am not a fan of this diff even when basically maintenance free..

@heinedenmark 5 лет назад

I had a Fiat Coupé 2.0 20VT which have this kind of diff. Works really well but is bad for the fuel effiency.

@girlshots1 2 года назад

yep

@0bigantney0 11 лет назад

Both of sides of the housing are filled with liquid, but have no pressure plates? When the tire on the ice rotates at the faster speed, the liquid transfers to the other side so torque can be transferred to the side initially rotating slower and create its own pressure to the clutch? With that being said, how does the liquid transfer? Via small turbine????

@Qkfltpdls777 Год назад

Can you use normal GL-5 gear oil to VLSD (Nissan’s R200V) instead of GL-5 gear oil with LSD additives?

@badtzlotus 11 лет назад

I was spinning it in gear with some gas at rate of about 10km/h speed so it was not fast, just so I wanna check. anyways, thanks for your input!

@ipodfreak93gh 11 лет назад

so it would be better to use a thicker liquid for say drifting?

@badtzlotus 11 лет назад

So that means it works? I had my car in the air with 4 corners on jack stand, 1. spinned one of the rear wheels with hand, the other doesn't spin 2. turn the car on, put in gear, gave gas, it still have one wheel spinning and the other barely moves one wheel fast + one wheel slow/barely moving = still working viscous? So getting the speed up or sudden accellerate will trigger the lsd to work? cause I still don't know if my viscous is still alive thanks!!!

@Jimmy.O. 9 лет назад

So there's a non-Newtonian fluid in the viscous diffs?

@calibredki2852 8 лет назад

just an FYI 350z use a VLSD system for their OEM cars, with the nismo diffs just being harder, stronger materiel for the gears... Now, why is the VLSD non-repairable/serviceable other than just changing the gear fluid in the differential???

@s.r.global7912 5 лет назад

I have an 04 350z and want to put a 370z vlsd but idk what to get to fit any advice

@sidharms7206 5 лет назад

Hey know you commented like 4 months ago but all you would need to do for ideal fitment would be to run 370z shafts and driveshaft

@GianLombardo 11 лет назад

So... Basically works on the same principle of automatic gearboxes?

@mwmorph 11 лет назад

Is Viscous the principle behind the Torsen line of diffs?

@m.morininvestor9920 4 года назад

Wich one is the best in a 2020 370Z ??? Open diff. or Viscous LSD and WHY ? thx all

@nixonwphoto 11 лет назад

Is the the viscous coupling kinda like torque converter?

@fightingfalconfan 11 лет назад

the oil does both. acts as transmission fluid and gear oil

@a6thomas574 2 года назад

Does this type of diff require limited slip fluid?

@coltenphillips8174 6 лет назад

My Miata has one of these

@annalango5884 9 лет назад

How could I fully lock my r230v up

@nrgrao1991 11 лет назад

the weight distribution ratio is 54%-rear and 46%-front...i hope you can help me out here...

@luiznicolau1857 6 лет назад

Dear, I need your help, I need to know if my Mitsubishi Airtrek (outlander I) has this, and, if yes, is it in front or rear diferential?! thanks! nice vid

@hyperlink3113 6 лет назад

Google search???

@alanphillips4431 4 года назад

Would this be more efficient by using a non-Newtonian liquid that doesn’t follow the laws of viscosity?

@bengleckl1877 2 года назад

What is cs gl5 fluid?? Controlled slip??? That the same as limited slip fluid ?

@civhonbmm3 8 лет назад

Now my question on Viscous Limited-Slip Differential (VLSD. Which of the 370z models have this type of Dif? Basically do all 370 have ( LSD ) differential? Or just the Nismo does?