Exploded View - Inside the Eaton TrueTrac Differential

[mariusesss]

what will happen if one of the wheels lift off the ground? Will the diff still work(the grounded wheel get 100%), or will the lifted wheel spin(get 100%)?

[eaxebxecxedx]

so basically this differential delivers power to the wheel that has the MOST traction?

[biggdaddy2001]

isn't this a thorsen type of gear set

[pogoboy123]

So is this how Acura's SH-AWD works?

[SparkDischarge]

@pogoboy123 Honda's sh-AWD is a front wheel drive PTO system. Instead of one clutch & rear differential, Honda decided to not include a rear differential, and use two clutches, one for each rear wheel.

Honda's system allows for 3 wheel drive. The idea is to not drive the inner rear wheel, in order to generate a torque upon the chassis, and increase rear outer slip angle, to aid in increasing yaw, and yaw rate.

[AllaaHassan]

Brake Traction Control + Helical (geared) LSD = Maximum Traction Solution with true auto-locking diff

I have the setup in my Explorer and I really love it

front end:

 27 spline, Standard Rotation, Dana 30

Rear End:

31 spline Standard Rotation Ford 8.8

[garciaarmando12]

is this locker puting in a front differential and is it worth buying for hardcore off roading how about if your going up a hill or in the mud and turning the front wheels would it still have a both tires spining at the same time ???

[Munky332]

@garciaarmando12 this is a geared LSD, not really the same as the locker you might be thinking of. While OK for offroading, a true locker would be better.

[LB6060]

Finally, I think I have a basic understanding of how these work. Has anyone ever used one of these in a drag race application? What kind of shock loads will it accept before destruction?

[MudBarf]

So this isn't actually a locker, then, but an automatic torque biasing LSD?

[SparkDischarge]

@MudBarf A torque sensitive differential locks, until the traction difference exceeds the designed torque bias ratio, then it differentiates.

re-watch the part where it shows the torque splits. 75:25, 50:50, 57:43, etc.

[MudBarf]

@SparkDischarge Now you're just confusing me. I know what an ATB LSD is supposed to do, and how it's supposed to react to differing traction conditions. What I don't know is what's *inside* one.

As for it locking, are you not talking about a clutch type LSD? That has friction plates that "lock" the two axles together until the difference in torque between left and right halfshafts during a turn forces the plates to slip.

I see nothing inside that could "lock" this thing.

[LB6060]

@MudBarf I think, basically, that the pinion gears get "locked" in their cups in the carrier, until in a turn the outside wheel over-runs the inner, causing its associated pinion gears to become unloaded and allowed to turn. Probably I'm wrong, but it seems similar to a standard open differential except that under load both axles are locked together unless in a turn.

[MudBarf]

@LB6060 Perhaps.

I think I'll email Eaton and ask them, because I would like new diffs (when I can afford 'em!) for my SJ, and an ARB style locker seemed best - now I'm wondering if this thing might work even better, because an ARB forces 50/50 torque split - if this can give the tyre with more grip *MORE* than 50% of the torque, in theory it would be *better* than a locker.

And since they make both, they'd have no real reason to lie to me about it (I hope!).

[SparkDischarge]

@MudBarf By locked I mean not differentiating, the locking friction is proportional to the applied torque, therefore if you are not applying positive/negative torque, this will behave exactly like an open differential.

Say you have a 3:1 bias, 50% locking. Each side carries 25% directly, and the remaining 50% is carried frictionally. Going straight, the L/R don't care who carries that 50%, start to turn (see LB6060's explanation of the overrun) and that 50% becomes the job of the inner, 75/25.

[MrOmarr1991]

I finally git 90% of it

[the1thatgotirwin]

those are bolts?

[n00b247]

Music from Stunt GP!!!

[cobalt120]

Hi. Good video.

There are a few odd things about the tru trac concerning the levels of power transfer.

Near the end of the vid. It shows different terrains. If you reduce that much power to one side that side will have more resistance(like an anchor) and will pull you to one side.

Like comparing sand to gravel or ice to sand.

It would be nice to have the option to lock both sides. When needed

[cobalt120]

@cobalt120

As it stands the tru trac is still the better option.

[SparkDischarge]

@cobalt120 It is LOCKED, until the torque bias ratio is exceeded. I would guess the limit is 3:1, hence the 75:25 under extreme traction differences left/right. A solidly locked differential can support 100/0 & vice versa, but you wouldn't drop to 0 % unless it was airborne.

[MudBarf]

@SparkDischarge I think you have that back to front. A solidly locked diff (or a spool) supports 50/50 distribution of torque to either halfshaft - it's a completely open diff that can support 100/0 (or 0/100).

[SparkDischarge]

@MudBarf A fully locked diff/spool does not care who gets what. L/R

Put a hoverboard under the one side of the vehicle, and the diff/spool will still rotate the airborne wheel at the same speed as the grounded wheel, and with as little torque as it takes to overcome the bearing drag. This will be as close to 0/100 as you are going to get.

Another example would be having two different sized tires, the diff/spool will, by design, rotate both at the same speed, but the torque will be different.

[MudBarf]

@SparkDischarge You seem to be confusing that a wheel uses and what the diff offers. I don't know about other applications, but in the 4x4 world we consider a spool or locker (not LSD, but true locker) to be offering 50/50. If a wheel is in the air, the spool still offers it 50% of the torque, even if it's using 0%. An open diff is the only type of diff that ever offers 100% of available power to a single wheel on a given axle.

[SparkDischarge]

@MudBarf Well that is just not true. Strain gauges can be used to empirically demonstrate that.

The open differential maintains roughly a 1.1 TBR. That is, the the non-spinning wheel gets 1.1x times the tractive torque of the spinning one, and the remaining applied excess torque contributes the angular acceleration of the already spinning wheel.

That is what brake actuated traction control does, brakes the spinning wheel to 'simulate' traction, which works through the diff to the other wheel.

[MudBarf]

@SparkDischarge Now, that's just nitpicking. You know what I'm trying to say. And you're ignoring the point I'm making - which is that the industry standard terminology (which you've pointed out is wrong from a mechanical engineering point of view - maybe it is, I don't know) is the opposite of yours.

I can see that your intention is to teach, and that's noble - but by using the terms the opposite way to the industry, you're just confusing things - which is the opposite of helpful!

[SparkDischarge]

@MudBarf The reason the industry standard terminology is wrong, is they don't really understand an open diff.

Lets say you put 100 units of torque into a diff. The spinning wheel only provides 10 units of torque of resistance/traction, the diff provides 11 units of torque to the other side, the leftover 79 units speed up the already spinning wheel.

Once they understand that, a solidly locked axle is easy to understand. Same speed side to side, variable torque-depending on traction 100/0 to 0/100

[MudBarf]

@SparkDischarge Those in the industry do understand an open diff - the reason the industry standard terminology is wrong is the same in any industry - sales.

Trying to sell this stuff to people who don't "get" the tech involved results in incorrect terminology. I had to deal with stuff like that all the time back when I was a sysadmin - for example, an ADSL router is, 99% of the time, not a router at all - it's a bridge.

You have to roll with it though, or you'll confuse people.

[dodty92]

accidentally clicked thumbs down lol. sorry.

[MudBarf]

@SparkDischarge It's not that I'm saying you have the tech wrong, just that the terminology (rightly or wrongly) you're using isn't the way people (at least, everyone I've spoken to, irl and on forums) use it. You're using it exactly the opposite way.

I see the logic in what you're saying, I really do - but it's confusing as hell (at least at first).

[SparkDischarge]

@MudBarf I am using the correct terminology, from a mechanical engineering perspective.

[stealth44082]

How does this work with c-clips on the axle shafts?

[jimday666]

holy shoot that's a lot of gears

[sakda357]

Very good animation.

[sinfulparade]

Fantastic! Right job, mate!

[lazzer408]

So how does this get any posi action? By cranking the planets into the housing walls? Seems like it's going to rip itself up quick. It's an open diff as far as I can tell unless the friction of the planets into the housing is enough to stop them from turning.

[SparkDischarge]

@lazzer408 Frictional resistance to differentiation is generated at: side gear to side gear & side gear to cover [depend on direction of torque transfer: forward/reverse], pinion ends to housing, pinion tooth face to pinion tooth face, center gear tooth face to pinion tooth face, pinion gear tooth end to housing.

Under extreme differentiation, a lot of heat can be generated. That is the biggest issue. Some run gear lube through a cooler.

[bftoler]

had one of these units installed in my 02 silverado z71....best thing money i ever spent on it...well besides my vigilante and trans upgrade haha..honestly though, huge difference, posi burnouts, great handling in inclimate weather, good stuff

[Neroscot]

Interesting perspective...!

[DontFlag]

wow, i thought locking diffs were as good as it got....

thats amazing, ima have to watch it a couple more times and see if i can get a better understanding.

[QuattroStig]

Great demonstration.

[braaaapp]

Can someone tell me if this is a LSD diff? Thanks!

[SparkDischarge]

@braaaapp 'LSD' is a marketing term. This is a torque-sensitive traction aiding differential.

[monkycheez]

What software do they used to make this animation???

[chromatic1976]

@monkycheez they used a program called solid works

[nnikitaka]

this is intresting where did you get the music

[berkelusa]

How much does this unit go for.. say used in a 1996 Ford Explorer 8.8..

[murry2010]

will 9in detroit lockers fit on a ford 8.8 rear end?

[gasripper2]

I have this unit on my F150 and when I get into some steep stuff only the wheel with the lightest load spins. I have tried applying some brake but it does nothing. I am not really happy with this unit.

[alcram]

@gasripper2 That is when you press the brakes to get some traction on both wheels. I know it sounds weird but that's what they teach you in the army to do and it works. The explanation is simple when you brake the light wheel slows down and it forces the locked one to go.

[Cheesecutter5]

@alcram I found out my Truetrac is broken. It needs to be replaced the small worm gears are broken. I think I am going to try an e locker

[deezynar]

@alcram

What vehicle do they tell you to do that with?

[alcram]

@deezynar it's on the older Hummer and military HUMVEE driving manuals somewhere that if you apply the brakes to the spinning tire, it will force some of the torque to transfer to the other side. This is the same thing a limited slip will do, take some of that wasted torque and transfer it to the tire with more grip by providing a certain amount of built-in "braking" action for each axle that simulates traction.

[deezynar]

@alcram

Thanks, that's interesting. Did you have a lot of traction problems with these units. Theoretically, you should be able to take one drive wheel off the vehicle and support the axle on a wheeled dolly and the remaining drive wheel should push you down the road.

[AlvinAZ]

@gasripper2

There's a video of a car driving off a jack. :)

What's up with yours not working? :/

Where you at?

Your problem with ice and snow by any chance?

Alvin in AZ

[gasripper2]

@AlvinAZ I had the wrong gear oil in it. I had synthetic and I went to the organic stuff and it works fine now!!!

[midyar]

@gasripper2

Could be synthetic gear lube?

I installed one my f 150 and love it. I use 80w 90 mineral oil , as per Eaton specs.

To test: I pulled one side of vehicle off road into snow and and other tire was on dry pavement and it would break the pavement wheel side traction with a squeal .Torque biasing at its best !

Too many problems with synthetics on these......

[HeavyChevyK10]

The music is Bangin!!!!!!!!

[chevyman8329]

its so simple!

[gasripper2]

I have this unit on my 4X4 F150 and on the really rough stuff I have to apply a little brake to get it to work correctly. I am not sure if I would go with this unit again. I may go with the ARB

[Resistolitin]

detroit true trac is the best

[ApalosRocks]

Excellent video!

[kingkruel123]

i dont understand how one spline shaft can go clockwise whilst the other goes anticlockwise

at 1:17 and again at 2:00 someone please help

[deezynar]

@kingkruel123

Actual opposite rotation wouldn't happen in a car, the video is exagerated. This diff won't allow the 2 wheels to rotate at different rates without both of them having traction with the ground. If one wheel loses traction, the slipping wheel will rotate at the same rate as the wheel w/ traction because w/ out traction, it can't rotate its worm gear to let the worm wheel rotate, thereby keeping both axles "locked".

[kingkruel123]

@deezynar Thanks mate... really helpful

[SparkDischarge]

@kingkruel123

It doesn't. Think absolute rotation. The 'camera' is rotating relative to the absolutely rotating differential assembly.

[kingkruel123]

@SparkDischarge yh it does... at 2:05 look at the tape at the end of both splines... one goes clockwise whist the other anti-clockwise

[SparkDischarge]

@kingkruel123 Again, if the 'camera' is rotating at a greater angular velocity than that spline, it will look to be rotating backwards. It is not. It is still rotating forward, the differential case is also rotating forward, and the other spline is also rotating forward. (differential case speed is average of both side gears)

The point of this animation is to show that a torque sensitive differential works BEFORE differentiations, and DURING differentiation. Proactive > reactive.

[FullTraction4]

I've got one going in my TJ's D30 in about a month with 30 spline chromoly shafts & greasable Ujoints.

[qxvmx]

so will it will it spin both tires during a burn out?

[911racer]

correct

[rotary57]

This is simply awesome.

[AlexanderA80]

Best animation about TrueTrac. It will be great if you add real demonstration on some car.