AutoLSD/4wheel sytem on 2015 Tundra/Sequoia - impressions??

crenca · Jul 26, 2015

Proud new owner of 2015 Sequoia (same drive-train as 4x4 Tundra) Perusing through the treads here I noticed that some folks don't rate the Toyota 4 wheel drive system very highly, and end up getting aftermarket lockers of various sorts. Putting aside the numerous posters who don't seem to know what a brake based/computer LSD system is, how to engage it, and complain when they don't have traction, how do those who actually are reasonably sure they know how to engage AutoLSD rate it?

There is a video posted on this site of the Dirt Every Day guys successfully running "hells revenge" in a stock Tundra (Pro yes, but the drivetrain is the same as my Sequoia). Now, if the AutoLSD did not "work" (at least to a significant degree - granted not exactly the same as a mechanical locker) it seems to me this run would not have been possible. Indeed, in the video you can see brief glimpses of wheels up in the air and the other wheel (on same axle) digging for traction. Obviously, the brake based/computer LSD system is "working". Now, could they do the same run multiple times without overheating the brakes? Perhaps not and thus I understand the reason for dedicated mechanical lockers - however, the Toyota brake based/computer LSD system can not be said to be "working" as intended.

Thoughts?

wildbill23c · Jul 26, 2015

Given the electronic nannies in these trucks the 4WD system will surprise you what it can do and where it can go.

That being said, its by far not the greatest. I am not a fan of the electronic engagement 4WD systems. This truck is the first one I've had with a knob for engaging the 4WD, everything I've had was manual shift t-case and manual hubs except my jeep which had the manual t-case with no hubs as it was full time 4WD.

The limited slip differential is non-existent in these trucks. The differential is 100% open. The Auto LSD works by applying the brakes to the wheel that is spinning faster than the other one, which somewhat tricks the differential into transferring some power to the other wheel.

I've had my truck for 7 years, and haven't had any traction issues and I've taken it down some pretty nasty roads in the past with street tires and pulling a trailer. Its a capable truck, but if I were relying on it in the back-country I would certainly want a better setup and I would want an older truck with manual 4WD...the electronic system really scares me to rely on it for any length of time. Never had a manual 4WD system fail, other than a manual hub started clicking one winter, which was a simple repair...but when you get into electrical engagement stuff and all the electronics involved that's where things go downhill.

The ABS/ALSD system can overheat, and you'll know when it does as it will not work until it cools down...I believe the ABS light will come on when the system overheats but I'm not 100% sure. During normal driving with these systems the ABS/ALSD performs fine, but I wouldn't rely on it in severe conditions as a way out.

Jaj23 · Jul 26, 2015

It works just fine for my purposes. No complaints.

bob2 · Jul 26, 2015

What 4wd system does my 02 tacoma have? The locker has saved my ass twice

wildbill23c · Jul 27, 2015

Your Tacoma had the factory option of having a locker or a limited slip differential. We aren't talking about the Tacoma

.

crenca · Jul 27, 2015

wildbill23c,

When you say:

"The limited slip differential is non-existent in these trucks. The differential is 100% open. The Auto LSD works by applying the brakes to the wheel that is spinning faster than the other one, which somewhat tricks the differential into transferring some power to the other wheel. "

I understand if you limit the definition of "limited slip differential" to a mechanical one. However, as you point out, a "Auto LSD", which is to say a brake based one, is in fact a "LSD" solution. Also, you are right in that such a solution is never a "locked" differential - the diff is still a plain-jane open diff. As such, by braking (more specifically, breaking it enough) the wheel that has no traction an open diff then sends all the torque to the other wheel which has "more" traction (though people seem to get confused at this point - assuming that the wheel with "more" traction will automatically have enough traction to move the weight of the vehicle, which is not necessarily the case and mechanical lockers can be in the same position).

I also know what you mean - an analog (i.e. mechanical) solution is no doubt better for "real" back-country driving. That said (not having had the chance to test mine yet - wife won't let me do any offroading until the new car smell is gone

) I was wondering if anyone had any first hand experience (after they correctly set the system) with this specific digital solution.

wildbill23c · Jul 27, 2015

There's no "setting the system" LOL. Its electronic. There's no buttons to press to select a limited slip axle just the computer allowing the ABS system to trick the differential when you engage the "Auto LSD". The differentials themselves are open or conventional differentials they have no limited slip differential workings. You can add one or you can add a locker...but from the factory the differentials are open.

A true limited slip differential has a clutch of some sort that will limited a wheel from spinning and transfer power to the other wheel on that axle. A limited slip differential DOES NOT transfer power between axles just between sides of that axle (Left or Right).

A locking differential has a clutch as well, or other means of mechanically locking both axle shafts together providing equal power to both wheels on that axle. Its a great idea if the wheels are on a surface where they can easily slip...otherwise you can easily break axles, bearings, differentials, drive shafts, etc.

This truck has neither of those setups from the factory. They can be added and there are several brands out there to choose from. As the truck comes from the factory like I said it has open differentials. it uses the electronics from the traction control, stability control, and the ABS wheel speed sensors to help lessen the wheel spin that would normally occur in low traction conditions. That being said if the other wheel on that axle doesn't have traction...you still won't move anywhere. The system cannot transfer power from one axle to the other just between the 2 wheels on the same axle. This system only works on the rear axle, the front differential isn't effected by the auto limited slip system.

Scottso · Jul 27, 2015

Auto LSD only works in 2 wheel drive. Cannot be turned on when you are in 4 wheel drive.

crenca · Jul 27, 2015

I wondered about this - I will have to re-read the manual.

wildbill23c, to draw an analogy from music, the "mechanical vs electronic" debate can be a bit like the "digital vs. analog". Which is better?

My personal suspicion (not quite an opinion I admit) is that "it depends". For example a torsen limited slip (a very common type) only is able to put torque to the wheel with the "most traction" as a ratio to the torque it is able to put down on the wheel with the "least traction. What this means is if you put an axle (or two in a 4x4) with one wheel on a near friction-less surface (say flat ice) the torsen diff won't be able to put any torque to the wheel with the most traction (no matter if it is on dry pavement) because 0 x some ratio is still 0. This is why rock crawlers need true lockers.

Soooo, an "auto LSD" would actually work better in a situation like a wheel up, or one wheel on a near friction-less surface, than a torsen LSD (and every other "mechanical" LSD as far as I am aware because they all have the same limitation if I am not mistaken - can someone confirm or deny?) because unlike the torsen LSD an auto LSD (yes, with an open diff) would be able to send torque to the wheel with traction.

However, just like music, it all depends on the quality of your electronics. Is the the Toyota auto LSD (or, in 4x4 mode with center diff locked, the standard traction control scheme) a good one? Is it a poorly encoded mp3, which sounds crappy even on a poor sound system? Or is it a better than CD quality 24/192 FLAC that just "works", and in some cases is better than a LSD and "just as good/nearly as good" as a locker until you overheat the brakes?

thisisdudewhoru · Jul 27, 2015

I wish toyota would have implemented actual a-trac and crawl control as seen in the fj, taco and 4runner. I felt that a-trac worked very very well. It is basically a very aggressive auto lsd though. Too bad the auto lsd doesnt work in 4wd.

wildbill23c · Jul 27, 2015

If you want it to work right you need some sort of mechanical connection. Electronics are only as good as the programming...and in many cases very lacking.

With a limited slip differential, you'll never have full lockup of both axles there's always some give to a limited slip system. That's where lockers come in, it gives a true mechanical connection between both sides of the differential.

For general driving though a limited slip will get you through quite a bit...however like I've said the tundra doesn't have limited slip its based on sensors and applying the brakes to the wheel that is spinning faster than the wheel on the other side of the axle. The military HMMWV's are the same way, they have open differentials front and rear and a select-able center locking differential...if I recall in the manual it was called biased braking but the operator did the braking to get the limited slip differential effect.

With an actual auto limited slip differential, the differential will limit the spinning wheel speed and allow some power to go to the wheel that isn't spinning as fast. That doesn't mean the slower spinning wheel has enough traction to move the vehicle, but the limited slip differential will slow down the wheel that's spinning the fastest and send some of the power to the other wheel which may or may not be spinning and may or may not have traction.

mdl · Jul 27, 2015

@crenca, The Alsd works as intended and most really don't understand it. I have changed out my brake fluid about 5 times now as I use the aLSD a lot.
I ran around for awhile just using the ALSD, would light up and burn rubber all over and leaves two nice strips. I installed a Auburn Pro LSD but still run with ALSD on for safety when hitting the corners. Having the nannies off it can get squirrelly if your not paying attention with the Auburn!! The 07's have the alsd where it cuts power but I can throttle through it and still have control.

wildbill23c · Jul 27, 2015

I noticed that the new Tacomas no longer have the select-able rear locker, they've now gone the nanny way as well like the Tundra.

bob2 · Jul 27, 2015

We aren't talking about the Tacoma. wink.

crenca · Jul 27, 2015

"For general driving though a limited slip will get you through quite a bit."

I agree. That said, for most folks, in the typical low traction situation they will find themselves in (mostly snow/ice, perhaps "fire road" somewhat muddy offroad, etc.) I think a properly functioning, well sorted out "Auto-LSD" or "A-Track" works better than either a LSD or a locker. Hear me out. I got in my father-in-laws then new F150 4x2 with a locking (not limited slip - fully locking) rear diff about a year ago. He was talking about it and said "when I push this button (referring to the locking diff) the whole truck vibrates and the tires "skip". Do you know why?". He had not a clue what a locker is, how it works, and when and when not to use it (such as dry pavement, the only time he had ever used it out of curiosity). After I did my best to explain when he would use it (almost never in his case) he admitted that the salesman had said something similar, but that he did not understand.

Or, take my wife for example. The Sequoia is her daily driver. The only time she will be using 4wd is in weather. She would not have a clue as to when to use a locker if there was one on the rear axle, and I am not going to ever have her lock the center diff (which is a torsen by the way) unless I am on the phone with her and she is stuck.

In both of these cases a properly sorted out electronic nanny system/auto LSD is simply alot smarter than these two drivers will ever be. They simply will never take the time to understand enough about mechanics/cars to know when to use "real", "mechanical" lockers.

Also, given that the Tundra/Sequoia 4wd system has two open diffs on each axle and a torsen LSD for a center diff, even in 4x4 mode if you put one single wheel on a near friction-less surface (such as smooth ice) then you are still going no where. You still need a brake based traction control system to brake that wheel so that all three diffs can send torque to other wheels.

Besides, as the ABS/traction control revolution of the last 15 years or so has taught us, electronic nannies are our friend. They are smarter than the vast majority (really, like 99.9 + %). Your "average" driver locks up the brakes in a panic stop, does not know how to turn into/recover from a slide, etc. etc. I am convinced that the falling death rate per mile driven is due in large part to these computers - even more so than the better crash worthiness of modern vehicles.

Anyways, I am a bit disappointed that the Tundra/Sequoia does not have Toyata's full "A-Trac" - or does it?? The video of that Tundra going up hells revenge seems to indicate that the computers ARE implementing "Auto-LSD" in 4x4 center diff locked mode (I assume that is what the Dirt Every Day guys had the truck in during the runs)...

Ontariotundra · Jul 27, 2015

ALSD only applies when in 4x2. You can select it. In 4WD the Tundra automatically engages A-TRAC if it detects slippage. You can disable it though if you want to run open diffs in 4WD however.

crenca · Jul 27, 2015

Now that I have had a second look at the manual, this is what I understand also.

A poster above (and others on other threads) seem to indicate that the Tundras/Sequoia 4x4 A-Trac mode is less than satisfying (compared to earlier Toyota products for example), although many of them seem to be comparing it to dedicated aftermarket lockers which I find can be a straw man because dedicated lockers can be more useful in their element (extreme low traction, rock crawling, etc.) but are not as useful "all around" (plain jane low traction, weather, etc.) and are actually stupefying to 99.9 + % of drivers out there.

BESIDES, as I pointed out earlier in reference to that video, if the stock 4x4 A-Trac can do "hells revenge", it certainly is no slouch in the "extreme low traction/wheel up" scenario.

BUT, which is it? It seems to me that almost all those criticizing it (and usually recommending after market lockers) are either not using it correctly, or expecting something for which even dedicated mechanical locker would not fix. This is at least my conclusion so far - willing to be convinced however that the Toyota Tundra A-trac is "crappy" - but then I suppose you would have to argue that Toyota gave the Dirt Every Day guys a non-stock/modified A-Trac. Manufactures do do such things unfortunately...

Ontariotundra · Jul 27, 2015

I have had good impressions of it however, I find it can limit itself in certain scenarios. You can hear it try and work but achieve very little and bog down ( ie snow) where I have found a rear locker is much more dependable to keep your momentum going. I have found that ATRAC works after it detects you are going into trouble which is sometimes too late depending on what conditions you are in. The locker let you lock and drive beforehand and have momentum to assist. I also found its easier to back out in snow after being stopped and reasses. I had ARB in a prior truck so I don't have any experience with a factory Ford E-Locker or the GM locker to compare. But being able to lock before anticipated challenging areas made a big difference to me and that's what I noticed.

crenca · Jul 27, 2015

This makes perfect sense and points to an important limitation of a "digital" solution.

That said, it is not at all surprising that a human head "anticipating" when to lock can be better than a computer, in that a computer can not "anticipate" at all. This does not mean that 99.9% of drivers can accurately anticipate (they can't). Your the exception that proves the rule.

However, your experience reveals why it is probably a mistake for Toyota to not allow "AutoLSD", which does not cut fuel to engine like A-Trac, in 4x4 mode...

joe's toy · Jul 27, 2015

My experience with the auto-lsd has been good. The most impressive demonstration I've personally experienced was while hunting for a christmas tree one year I pulled off the road into snow. I tried creeping back onto the road but my tires just spun so I turned the auto-lsd on and drove right onto the road. It does feel a bit strange when it's working but it did it's job without me having to turn the 4x4 on. I like that it has the option vs some open diff trucks with no traction options.

nitroscope8 · Jul 27, 2015

I can engage auto lsd while in 4wd. Maybe the 14+ is different?

Yuckfou · Jul 28, 2015

There is a lot of misinformation in this thread.

Put your 4x4 in 4high, leave the trac button alone, now floor it if your in deep snow or mud, you hear a lot of clankin and weird noises, that is the brakes making traction to all four tires.

push the trac button, floor it, tires spin and well no noise.

Put it four low, now the same things happen, but at less wheel spin, the brakes engage the faux lsd. Basically atrac.

It works excellent for what it is.

drdripps · Oct 24, 2015

I have read these post with interest, but I think most owner of a Tundra 4x4 will not use their as a rock climber. Most owners ,myself included, will only use the ALSD or 4WD occasionally. As for myself I will use it when I go to my mountain house in the winter and I run into ice and snow and occasionally on a muddy or sanding fire service or dirt road on fishing trips during the summer time. I hope I am not mistaken but from reading the manual the Auto LSD/A-trac is automatic when in 4WD and there is no need to engage it by manually pushing the button on the dash. So my feeling is that for most of my driving the system should be just fine. I will say that I have an older Tacoma that has been built a little bit as a toy that I can beat up on the weekend or tow for more aggressive fun.

wildbill23c · Oct 25, 2015

You would be correct. You can select the "auto-LSD" when in 2WD mode by pressing the traction control button, but in reality there isn't a limited slip differential in these trucks period. Open differentials front and rear as most 4WD's actually are. They used the traction control system and ABS system to make the truck act like it has limited slip differentials by applying the brakes and slowing down wheel spin and tricking the differential into sending limited power to both wheels.

The Tundra is a bit large and heavy for any major offroad use, and the price they sell for makes it that much less of an offroad use choice LOL.

MobyDick2010 · Oct 25, 2015

I feel it's a pretty straight forward process. I feel like the ALSD is good for the average owner, who's idea of off-roading is going down gravel roads. It's is perfectly good system then; you start spinning on gravel, the "LSD" brakes on the slipping wheel, and sends some power to the wheel with more traction. Now if you turn off the nannies, this becomes less invasive; it allows more wheel spin and less correction, it also reduced the engine cut back on power.

Now in an off-roading situation, nannies fully activated, could leave you seating, wondering how that Chevy is doing better then you. Once you turn the nannies off, well you got an open diff with less engine interference.

Know the ALSD in its own situation, works perfectly fine. Outside of that though, it could leave you wishing for... More.
That's when you get into the case of LSDs like the Auburn Pro. It's a friction-clutch based LSD, meaning when it is in mud (2wd) both tires are getting a 50/50 ratio of power. The LSD is locked until it gets into the situation, where enough friction is applied, and it is allowed to 'slip'. Much like turning a corner on pavement. So until it has enough friction to release, it is locked.

The LSD I'm telling is totally mechanical and adjusts to the situation it's given, much like the ALSD, except it is more flexible.

And the unlocked/locked lockers don't really need going over.

Blenton · Oct 28, 2015

If you want it to work right you need some sort of mechanical connection. Electronics are only as good as the programming...and in many cases very lacking.

The brake pads and rotors ARE the mechanical connection in the ALSD. In a traditional limited slip differential, there are clutches or gears that use friction to transmit force. The brake pads on the ALSD do the exact same thing, the are just outboard of the differential housing. And the programming is very well done, IMO, for the intended purpose.

The military HMMWV's are the same way, they have open differentials front and rear and a select-able center locking differential...

HMMWV's actually have Torsen differentials which are a form of limited slip originally based on a worm gear design, though there are three iterations now. The design is quite novel and intriguing - simple but out of box. They are very effective and, IMO, one of the best designs.

Anyway, back to the OP's question: I find the factory ALSD to be effective and pleasant in most situations. When I first bought my truck, I was used to open diffs or a worn out factory clutch-type LSD. With double the horsepower of my old vehicle and an intrusive nanny system, I cursed the ALSD... until I learned how to actually use it. In 90% of the situations where I've needed traction beyond a paved road, I've found it to be great; it gets the job done and finds traction. I even took the truck down to Moab this spring and did the White Rim Trail along with some of the off-shoot trails. Most of the trail is easy going, but there are several bits and parts that can be white knuckle. The truck climbed like a billy goat and always found traction when it as needed. I don't recall a single instance on the trip where the tires slipped for more than an instant before grabbing hold of something. It was amazingly sure footed.

The other 10% of the time I've found myself wanting more. Those instances are limited almost exclusively to mud, fishtailing on purpose, and spinning donuts in the snow. The thing these all have in common is wheel speed; the ALSD does not like excessive wheel speed, which is sometimes needed to clean out the tires so you have more biting edges. The only other situation that I've found it to be somewhat lacking in is loose, gravelly, washboarded, uphill roads in 2wd with nothing in the bed. This causes the backend to bounce a bit and lose traction. Instead of just spinning a tire for a second and motoring through, the nannys cut power until you find more traction. The washboard ruts make this cyclical and annoying. But simply pushing the VSC button once to enable the LSD system is usually enough to stop it from bothering me. It allows a little more throttle and more wheel spin before cutting power, but it also pules the brakes more to slow the spinning wheel.

Overall, I think the system works very well for it's intended use. That being said, I'm looking at an Auburn mechanical LSD. I don't feel the factory system has let me down but I've been doing and plan on doing more backcountry exploring and would like to alleviate some of the stresses put on the braking system and drivetrain by using the ALSD so often. And, honestly, I want the truck to spin donuts like a chef in a cop shop!

I like getting my vehicles sideways when the powder starts falling here..

derp · Oct 28, 2015

What ever happened to the rumored aftermarket LSD with e-locker? I forget if that was Auburn or Eaton? Couple years ago it was a year out?

derp

Zackbremer · Oct 29, 2015

also dont forget the atrac system requires a little tire slip, when i first used 4lo, crawling up stuff and the tires would spin i would stop hitting the gas, for fear of losing my line or digging a deeper hole. but the truck needs to feel the tires spin in order to lock that side and transfer power to the side that has traction....now i apply light throttle under 2000rpm let the well slip for a second or two and the power transfers to the other side and i crawl right up......the system works really good, just need to know how to use it.

BlackSnowSlide · Oct 29, 2015

I put an Auburn LSD in my truck. I decided to add a mechanical LSD after I was pulling the boat up a slippery boat ramp and the Electro gadget LSD that Toyota supplies in their computer system proved its shallow limits. I think Toyota's LSD is more a part of the ABS system to improve ride quality on wet streets under normal conditions. If you'r looking for a real change in quality traction, a mechanical LSD is a much better option.

AutoLSD/4wheel sytem on 2015 Tundra/Sequoia - impressions??

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