Understanding Limited Slip Differential

Right? Millions of wheel-holders out there will never have the slightest idea of what is actually happening every single day when they drive somewhere. I think this is why the auto hobby is such a fanatical group. There's so much beauty in a vehicle. The engineering is inspiring. The craftsmanship is breathtaking. The privilege to command all of these combined parts is exhilarating.

I agree after watching both videos of limited and non-limited slip I still can’t wrap my head around it

Actually it's the Engine or Motor that makes the vehicle move.
The Transmission helps the powerplant overcome the weight of the vehicle, particularly when stationary.
That's why Heavy Trucks have eleventy million gears !
Additional velocity and reducing engine rpm is a useful by-product.
Genius video though.

@@0utcastAussie It would be _impossible_ for an automobile to...well... be an automobile without some sort of gear/lever concept

@@inawrocki207
?!Z,
Al

+videobenji Do you even study a second language?

***** Right, other people study other things, not only languages.

+videobenji that is not very efficient

***** From who studies plenty of languages this is one of the dumbest things I have ever heard... you can't fully learn a language
L'obiettivo, qui, era trasmettere un concetto (in realtà è il traguardo di ogni singola comunicazione), cosa che è stata sufficientemente raggiunta. Si è capito male qualcosa per colpa sua? Non mi pare... ha solo ignorato un articolo, il resto è stato trasmesso bene.

***** People don't often learn a language with an accurate learning line, even some basic grammar can be not respected by native speakers
Mistakes happen
Did you understand my italian message? I didn't want to bother translating anymore

***** Engineers are crazy.

+Ciber X Gaming this is why kids used to play with tinker toys and blocks n shit...teach em to make this shit up

+Ciber X Gaming
It comes from a bunch of small iterations. They didn't just sit down once then after make it perfectly.
When a lot of people but a lot of time into something the product can be mind-blowingly complex and alien.

+Ciber X Gaming it wasn't people, it was Dr. Porsche

Damn, I wish I had taken Mech Eng. Things are interesting this side

i see what you did there.

Yeah! Trac lock si better

its a slipperly slope

A MAN OF HIGHER SPIRITUAL CULTURE

*grippy stuff 😉

@Will Black of course somehow you turned it into a race problem

@Will Black lmfao

@@hussam9044 I am really late. But do you still remember what he commented?

@@KorpiSoturi1 nah mate it's been 9 months, the pandemic wiped my memory lol

It's just about understanding forces and movement but the math part yea 'eff that lol.

Jan Šinkovec the thing is they're slip is relatively intermittent. Also, think wet clutches on motorcycles. Those actually take more continuous abuse. The important thing to do with wet clutches is replace the fluid as instructed. You do that, they actually last a long time.

they last long because of the fluid.
clutch packs in automatic transmissions for example will burn out quickly if you attempt to drive on low transmission fluid.

Andrew the reason clutch packs in automatic transmissions burn out quickly when driven with a low fluid level is a lack of hydraulic pressure to engage either the clutch packs or the bands it is not from a lack of lubrication however you are correct the special lubricants used in a LSD prevent premature clutch wear and of course the dreaded clutch chatter

@@insulman100 Another nice thing about a LSD is if the clutches do fail at some point the differential just acts like an open one. So at least you are not stuck somewhere if they do end up slipping. Well... unless its in the mud.

My 442 has a12 bolt "posi". My first few drives felt like it was crabwalking on any corner. I pulled the cover and saw nothing but clean 90 wt gear oil. An old buddy that ran new Chevelles back in the early 70's picked me up the GM posi differential oil and it made the difference. Hooks up leaves 2 10" black marks and doesn't feel like it is fighting itself.

Eric Southard oh you 💁🏻‍♂️

You made it sound like it's a drug

@@arinb.756 true

Thc for me

Boy😔

But listener should be aware of clutch pack.

Hey what about a thrown rod?

@@sneez9461 Bluesmobile :P "I think it's thrown a rahd" XD

Cave man no use "the".

When I travel through Europe I am amazed at how fluent people are at swapping between languages. Interestingly, those who learn a language most quickly are those who aren't afraid to make grammatical mistakes. Instead they focus on getting ideas across. For the most part, listeners politely focus on what they are trying to convey rather than less important details. As you say, this is a brilliant description of the mechanism of a limited slip diff.

did you get a good mark

@@ockertoustesizem1234 lol I don't remember it was 3 years ago

@@dannybrown3870 cars are just as addictive though

@Jason Sounds like you either have an open diff or bad clutches in your lsd.

The wet wheel slips,
Causes wheel spin,
Side gears push apart from spider gears,
Dry wheel gets traction?

@Jason I agree with you and I've had many vehicles in my 50+ years of driving. It always looks good on paper!

@@jkeldoc1893 If you've had vehicles with and without LSDs, of any type, you would know immediately how important an LSD is.
I can't stand driving open diff vehicles. You'll spin a single wheel rounding a corner all the time. Simply doesn't happen with an LSD,

Best 2 winter cars I had was a mazdaspeed protege with a factory lsd and a fiesta st that used the abs system to apply the brakes to the wheel that's excessively spinning adding resistance that "fools" the open diff into acting like a limited slip.

The pessimist says the glass is half empty. The optimist says the glass is half full. The engineer says he needs a 4.2 million dollar research grant to investigate the possibility of redesigning the glass using the Bernoulli principle of fluid dynamics along with changing ar......

@@stoopidbastid6420 Ok but what if the ingineer is pessimst or optimist?

Just don't drive while on LSD...

@@thhseeking sadly I already did many times lmao 😂

Julian Best if we’re talking, we need grammar.

The problem is you're not the type that needs it... therefore it seems fine to you. For beginners, this is terrible. I need even more explanation of parts and why things like "separation force" actually cause something to be together, etc... things like that are not going to be understood by a lot of people.

Найди ошибку в работе описания lsd😁

@Peter Evans "Picture yourself in a boat on a river..."

@Daniel
A '65 huh ?
I bet that could have some extra mileage over the years but as you mention up to the owner in the end.
I got an In-Tune i2 last month you can set the speedo/odometer value with that tuner for any desired axle ratio.
Now my car only logs in ~66% of my actual miles driven and turns out it only has 43k miles, which was the mileage I bought it with back in '13.
I can also run better on high octane gasoline now, best $270 spent 👍

I was wondering the same thing. It sounds like it was written by a real deal engineer whose first language wasn't english (or as someone pointed out below for teaching english to ESL-type engineers) really informative video but yeah the lack of definite articles is a bit hard on the ear

Thank you! I was thinking the same thing! I couldn't concentrate on the video because of the way he kept using all this baby talk! >.

Perhaps Indian or Russian English?
The engineer was ESL, wrote the script, then it was narrated by a voice talent who didn't know where the "the"s were missing, because the voice talent wasn't technical, even though he may be a native English speaker.

They are not used in Hindi.

I can offer to put the script into standard well-formed English before it goes to the voice talent.

it's trippy mane

@_@

Nice

Yo

Yeah, for engineers. If you're an ordinary guy like me who has no background in math, physics or engineering, then you won't understand a god damn thing in this video.

Bro, but i am an engineer.....and i understood everything....:P
If you want to understand this you just have to spend your hour...google about the topic and u will be all done bro..

_garry's mod metal collisions can be heard_

Just a missing animation of spider gear

Yea thats just sloppy, this video does a poor job explaining the steel plates very well.

Years ago a friend who drove a car with a limited slip differential reported the same thing- he said it was unnerving .

A very interesting and valid observation ! Thanks for that.
Were they front or rear wheel drive ?

>traction control

When I was a kid, one of the cars my family had was a 1978 Pontiac Catalina Safari station-wagon. I would have been 16 in 1978 when we ordered it. One of the options we got was an LSD. However, none of us really understood what the implication of it would be for driving dynamics (we were not a “car people” family). At the end of our driveway there was a (thankfully small) drainage ditch next to the road. One winter day, with snow and ice, my mom was backing out of the driveway and the car got stuck near the end of the driveway. The rear wheels happened to be lined up with the drainage ditch. I got out to look at the situation, and then in one more attempt, my mom gave it some gas. That made the rear end of the car slide sideways, and one wheel went off the driveway into the ditch. If we had an open diff, such an event would have been less likely to occur.

@@kc9scott All helped by it having an automatic gearbox. With a manual, you can more easily keep the revs low and instantly stop rotation by pressing the clutch - to stop a sideways slide.
In slippery weather, it's much better to avoid stopping in ditches and hollows !

DO NOT add modifier... it makes the clutches slip more and will glaze the friction surface making it harder to lock.

@@kleetus92 I'll listen to both of you and add half of the recommended amount of modifier

Yeah and seals and oil. My dad once did pay attention to that and well he ended up learning his lesson by spending a lot of money to fix the diff.😂

Man, Stuart, I have recently been working to figure out how this could possibly function. There didn't seem to be any reason for an axial force if one wheel is totally free wheeling. It seemed like the freewheel or even the low traction wheel would result in the spider gear rotating, at which point there's no separation force on the beveled spider. But the angular momentum not only makes sense, it matches a video of a Ford Transit (what I have) peeling out on one wheel on ice for a second or so, then the other wheel kicks in, presumably when the angular momentum and ensuing axial force became so great against the high traction side that the plates locked. Can you break this down in even more detail? I think I already got it all, but I've got a thread going on the Ford Transit forum where we're trying to understand the limitations of the Ford Traction Lock rear LSD. The core confusion seems to be some people say that when one wheel is totally off the ground, no power will reach the high traction wheel. But that doesn't sound right. Why wouldn't angular moment build even more quickly. I guess there's a limit to how much could build and how much force could make it through to the high traction side, but either way, the LSD should work right? Is there a time delay to build that angular momentum? However long it takes to spin up the free wheel however fast it takes to build enough angular moment in the spider / side bevels to sufficiently lock the high traction clutch pack? Many thanks for your excellent input. No other comment came close to answering this critical physics, and even the main video just blew past it leaving an obvious question mark. Cheers.

mike wilson I second this ^

mike wilson if your hung up on grammar, definitely don’t go from here to the donut media video explaining it. I was there first and ended up here for closure lol

It's the force caused by the wheel with traction pulling the axel to the side. It's a very small amount of movement but it's enough that the torque of that movement pulls the clutch pack together causing them to be in full friction and essentially lock, giving that wheel most all of the power, while the other side is having the axel pulled away giving space between the clutch pack disc's and allowing them to spin freely, limiting the power that goes to that side. Hopefully that made sense.

Just don't get addicted to LSD

so what he said

@@Unknown-vp2vt No, he said that with an open diff the wheel on ice gets high torque and the wheel on dry ground gets low torque. That’s wrong. They both get equal torque.

@@NH2112 you didnt get the joke

@Peter Evans Let’s say you have 2 nuts, one torqued to 500 lbf-ft and one loose. You apply 500 lbf-ft to each nut by putting a 250lb weight on a 2-foot lever and letting gravity pull it down. Where does the missing torque go on the loose one?

@Peter Evans if you don’t have a limited slip or locker, the spinning wheel will keep the wheel on a solid surface from spinning. It will only get as much torque as the spinning wheel does because an open diff can’t do anything but apply equal torque to each axleshaft. That’s why a military Heavy Expanded Mobility Tactical Truck (HEMTT) with a 12l Detroit Diesel developing 445hp and over 1200 lbf-ft, putting that torque to 4 open diff drive axles with 6.17:1 gearing and 16.00-24 tires will sit there and spin the passenger side wheels when they’re off the ground in a ditch and the driver side wheels are on the road.
Torque comes from resistance to force applied. The loose nut in my previous reply doesn’t get 500 lbf-ft applied to it despite the fact that there’s a 250lb weight acting on a point 2 feet from the nut.

This video is incorrect. Just look up diagrams of locking differentials for reference to what I’m about to say. Capturing either side gear will affect the opposite side gear. For differential action to work the spider gears allow for infinite rpm difference between the two side gears by vary the rate that they spin in opposite direction. This is relative to the carrier, so even though one is spinning in reverse it’s still rotating forward since the carrier is rotating much faster thus allowing for rpm difference between wheels.
.
By capturing one side gear you prevent the spider gears from rotating thus force the opposite side gear to rotate at the same rpm excluding clutch slippage. This is why selectable lockers only capture one side gear.
.
The video asserts that the clutch pack on the side is what transfers torque, but that’s incorrect. Torque transfer is dependent on how much force the tires can generate due to traction. Lift a wheel and that wheel can no longer generate torque. This is the same as stripping a screw from over tightening. You keep imputing torque and it gets higher until it snaps and despite whatever force you try to impart it will just freely rotate without developing any torque. Open diffs are actually 50/50 split, so the lifted wheel generates no torque and the inside wheel will not generate any as well since the distribution is even. Now, moment of inertia can cause torque spikes so when you have a lifted wheel and floor it some torque is developed and can sometimes be seen by the chassis trying to move forward but once the wheel acceleration slows down that torque dies off because the torque to maintain rpm is far lower than what is required to accelerate. This can be seen by chassis lurching (rocking) in those situations.
.
A locker will allow both wheels to develop as much torque as possible before either slips, so does a clutch pack LSD to the extend that the torque cannot exceed the forces generated by the clutch pack. So depending on the conditions, the lsd and locker inherently bias torque.

Low Traction side has higher Rpm
So, Low Traction side gear will push the clutch
Also, the case would be rotating in opposite direction so the clutch would arrest the motion of Low Traction Side. This would act as an additional Traction on that side for the spider Gears.
This would make the Spider Gear transfer more power to High Traction side.

Low traction or slipping wheel will rotate at higher rpm and the other wheel due to high torque will move the vehicle when we use LSD .

It's insane that anyone would be turned off by knowledge, troglodyte.

computer voice

To me it sounds like technical English, where unnecessary repetition is avoided.

@@johnwebster4348 Sounds weird indeed. Not sure it's a mistake though, correct me if I'm wrong but the grammar is ok. It's just used in an awkward way.
Maybe it's one of these genius engineers who thinks in numbers and formulas only, and struggles to make even the simplest sentence because he's been so busy studying that the only time he's seen other humans and daylight is on the way to university.
And yes, English isn't my first language either, it's actually my third, so sorry ;)

@@Amber57499 -- "The steel plates *have* external tabs" is simpler than "The steel plates *are having* external tabs" so I don't see why it wouldn't be used. Furthermore, "having" is incorrect here.
Both "have" and "having" can be used when you experience an action. For example: "I am having lunch tomorrow", "I have lunch tomorrow". There are subtle differences is usage based on regularly and whether you're talking about the action or the idea of an action.
We're not talking about an action here though, "external tabs" are not an action. Only "have" works here, since the steel plates *possess* the tabs. This is partly where the confusion happens too, since you can possess an obligation for an action in the future, and talk about it as if it was an item you own, which is how "have" snuck into the other usage.

I have lunch tomorrow is also not correct, you can't use a present verb to denote a action in the future.

Changing the fluid more regularly than in an open differential helps decrease the wear and tear on the clutches provided the correct fluid is used. Yes, the clutches and steels will need to be replaced at some point, but it's not normally much more work on top of replacing worn bearings and seals inside any car's differential anyway; only a little more costly. Most normal road cars with an LSD that haven't been totally thrashed can go their whole life without having a differential rebuild and maybe only two or three LSD fluid changes.

***** Thank you for the perfect reply :)

Johnny Eighty That is what Angus said. You have to change the fluid more often in an LSD than in an open diff. He was referring to LSD in his comment, not an open diff.

+Johnny Eighty Ummm, do you even comprehend English?

+Johnny Eighty Your novels are inspirational! 👍🏼

They are now. Many come with open differentials that use a computer to brake spinning wheels. It's a lot cheaper and works just as well if not better

@@Aashishkebab Yes, but what about the cost of repair, cost of diagnostic, and complicated mechanism involved.
Saving on the upfront cost does not usually result in saving in the future.

@@clintonmahoney3396 Many traction devices today just use an open diff and brakes like the previous comment stated. It is a relatively simple system when compared to LSD. A computer just applies the brakes to wheels that are spinning out. The only extra component is the computer (which all modern cars already have) and the brake controller. The LSD shown in the video wears out pretty quick. On every turn the clutch packs are worn, eventually the LSD has to be rebuilt.

@@Redtooth75 I understand and I can certainly see how the modern computerized diffs work just as well or better. I prefer old engineering but I'm thankful for OBDII as well if you see what I mean.
Originally I meant that I was pleased how all these engineering solutions come about before the time of the computer so that we have them now.

Also, to be fair my Ford 8.8 LSD lasted 320,000 before I rebuilt the clutch packs.

I think even the animator got confused

It's not the only time the animation gets it wrong but for the most part, it's not important !

lol

You mean "Right side gear spinning slower than left without spider gears rotating". You used too many "the" XD

Or the narration was originally meant to explain something else at that part 🤔

Sam C sure... thats a voice generator

"Steel Plates are having external tabs"

DasEtwas You don’t think so, huh? 🤦‍♂️

You understand what is going on. I didn't see your response before posting here, but I went through the entire thing explaining how it actually works.

soxredsox I would like to not get my video stolen either so I understand that
And it isnt that big propblem

I find it essentially unwatchable. I cant move my fixation from the letters...

Yeah it sucks and is very distracting, to the point that I can't finish watching it. Krzysztof Dolecki anyone can upload anyone else's video to their channel as long as they don't monetize it without the creator's permission. Anyway, how is the watermark going to stop anyone from "stealing" the video, as you say? And it is a big problem when they're trying to visually show us how something complicated works and they put a bunch of writing right over the middle of it. Here's a better video that was made in the 1930's: krplus.net/bidio/e5iCmqKnm6XGiJQ

I didn't even notice there were letters over the moving parts

Then you're either blind or lying.

lol

Clutch pack is not happy. Clutch pack is sad.

@@_BangDroid_ everyone ask what clutch pack is, but never how clutch pack is

To some degree you are right, this design will increase fuel usage and wear tyres a little more.
However you missed how the design works when you said "if one wheel spins freely in mud there will NOT be high torque applied to the other wheel just because it's stationary, because the differential always 'shares' any load".
What you missed is the torque going into the wheel of firm ground causes the spider gears to put pressure on BOTH clutch packs, effectively locking the diff together. The higher the torque going through the differential, the more the packs or forced together, resulting in both sides receiving the same potential torque.....even if only one side requires that amount.

James Bradley you read my mind lol, please help

69aussieguy it would be awesome to have some centrifugal clutch, where if there's a high difference in speeds between the two axels, then the diff will, to some degree, lock up to provide more torque to the standing still wheel.
Obviously it's not going to work as well as a button operated differential lock, but it will help.

Ben 1337 Yes that would be nice. It all comes back to cost, it's much easier and cheaper to have a straight diff lock operated at the push of a button than some fancy mechanically operated system. I think some modern vehicles use sensors to adjust the clutch pressure to even out traction, but I could be wrong on exactly what they do.

69aussieguy Actually when I posted that comment, I looked up centrifugal clutches, then looked at how they could be implemented in the existing clutch.
What I actually thought of, would be putting a pair of some quite standard centrifugal clutches linking the differential pinion and the differential cage, that when the pinion spins too fast (which only happens when there's a change in wheel speed), the clutch would help increase the amount of force it would take to continue turning the pinion, thereby increasing the torque applied to the wheel.

SinisterShadow yup any car.. just brough an lsd for my 08 335i

thanks irani

Giorgio Irani lol thats why i looked up this video , just bought Quaife LSD

monaro srs? U have IG? Mine is Giorgioir

i have a 2007 e92 335i

you need to upgrade your brain first otherwise the video is ineffective