Why the auto LSD on a 4x4? (non OR)

2015 non off road, why in the world would I ever use the auto lsd when it seems 4h would be much more useful in getting me unstuck?

I know this as been discussed at length but I have not seen this question asked, wondering what situations people with the same setup found the auto lsd useful even with 4x4 available with the flip of a switch?

 

Autolsd also works in 4H also its a moderate way to transfer power from slipping wheel to opposite side to my understanding. It works decent nothing like ATRAC on the OR. Install a trutrac an it works great with the factory system, one of the best mods Ive done to mine

 

I was under the impression that I cannot activate the auto lsd in 4h. I know the light does not come on when shifting into 4h, you still have to press the button to activate it in 4h? Guess I need to do some experimenting.

 

For street driving the truck automatically limits slip of a spinning wheel to better apply power to the wheel with traction. Open diffs apply the power to the wheel with the least traction, which is far from ideal. You don’t need to be in a 4x4 situation to benefit from this feature.

If you are parked on the street facing up a steep hill with one rear tire on loose gravel and one on the concrete, you may just end up spinning the tire in the gravel and literally going nowhere. You shouldn’t need to manually put your truck in 4wd to pull out of your parking spot on a street. In this scenario the auto LSD would engage and apply power to the wheel on the street rather then sending all power to the wheel on the gravel, allowing you to pull out of your parking spot with no drama and no manual intervention to get your truck ‘unstuck’ from its urban parking spot.

Even just accelerating on the street in the rain when it is slick, the feature can be useful to minimize rear tire spin. Again, not a time when you would put in in 4wd.

 

I get the pulling out of a parking spot scenario - good point.

For accelerating from a stop on a slick surface I've always just popped it into 4h.

 

You get the Auto LSD in 2 high and 4 high. You don't get it in 4 low without doing the yellow wire mod - which is a handy 3 minute free mod if you off road at all.

 

Got it. I don't do to much off roading. THis is more out of curiosity as the auto lsd seemed redundant with 4x4 available.

 

Not at all redundant. In 4x4 only 2 wheels are powered - one up front and one in rear. If one of those slips too much the truck transfers power to the other wheel on that axle.

 

Auto LSD still works in 4hi its just confusing. If you are in 4hi and tap the traction control button only the trac off light lights up, not auto lsd, but its doing the same function. as 2hi and auto lsd.

 

This clears it up. Wonder why the light doesn't come on in 4h? Thanks!

 

@David K has a whole thing on the different traction modes. But yeah toyotas wording on all this is a lil nuts.

That stated, i never use the "auto LSD" function. If i wanna mess around, thanks to the locker anytime mod I lock the rear end in 2wd and go ham. If i dont wanna get stuck I am already in 4lo, rear locked with atrac on.... 4hi only gets used on icy roads and i havnt had a situation where the throttle modulation put me in a bad spot (that wouldnt be present with auto lsd / trac off)

 

When you shift into 4H you automatically have front and rear LSD. 4WD with LSD gives amazing traction. In 4L you have open axels no LSD. There is an easy mod you can do so you can have LSD in 4WD.

 

Yup. I feel the same way. I don't see myself ever using the auto lsd when I have 4x4. Maybe to pull out of a sketchy parking spot like was suggested above that's about it. I did read through David's post.

 

Even then with standard vsc / traction control, it should do its job just as good to get you out of the parking spot. Only thing auto lsd has over standard traction control is ability so spin up tires (no throttle modulation).

 

That's not really a good way to describe it. While TECHNICALLY correct, since you do use the word "power", it is somewhat misleading, especially for those who don't quite grasp the physics or the distinction between power and torque.

In actual fact, an equal torque is delivered to both wheels of an axle. Whether a wheel is spinning or stopped, the torque is still applied to it. The reason why it *seems* that only one is getting any action (hence all the power, but not all the TORQUE), is that you're spinning the one with less traction -- because torque and power are related by SPEED.

To put some purely made-up numbers to the situation in order to make it more clear, imagine that you are in a situation where you need 100 footpounds of torque in order to move, but the low traction wheel can only deliver 10 footpounds. Then the two wheels will apply 20 footpounds in total -- still only 1/5 as much torque as needed. You can't deliver more torque to the high traction side, because all the way up to the redline, the energy will be dissipated by the low traction wheel.

And so what the LSD does, is it partially binds up the low traction wheel, allowing more torque to be applied to BOTH axles, hopefully enough that the two together will exceed the minimum needed in order to move.

 

Its all about naming things. TRAC **is** ALSD, but in 4wd.

Now for the benefit(s) of ALSD in 2wd on a vehicle with 4wd....
1) Switching 4x4 on and off is clunky and slow, and a not entirely predictable process. It takes at least a couple of seconds, if you're lucky and the shafts line up. If the shafts don't line up, then you need to convince the shafts to turn relative to each other until they line up and the collar can slide over them.
2) Power sliding can be extremely unpredictable in 4wd, and is downright disabled in 2wd, until you switch from VSC to ALSD. Power sliding is extremely useful for maneuvering in tight quarters. For example, with a power slide, you can turn around on a 2-lane road without having to resort to a 3-point-turn. Just hit the ALSD button, crank the wheel over, and stomp on the go-fast-pedal.
3) ALSD can be applied *while in a slip* and engages immediately, unlike 4wd, which would cause your transfer case to explode if it allowed you to try.
4) Driving on **MIXED SURFACES** -- i.e. patches of high traction and patches of low traction --> Not so great in 4wd, especially if you have to steer on them. ALSD will offer you greater traction on the slippery sections, without binding everything up on the grippy sections.

 

The Auto LSD light doesn't come in in 4WD because it is the name of a 2WD system. Basically, it is the TRAC limited slip but without any engine regulation (throttle cut) that TRAC does to prevent tire spinning.

In 4WD (High), that enhanced, no regulation mode has been called TRAC OFF since 2012, and needs a quick button push. 2009-2011 it was simply called TRAC, but in H4, the engine regulation was off and there was no button push needed to turn it off.

Important to note TRAC OFF is not Trac turned off, it is Trac with engine regulation turned off.

To turn TRAC off, so you have old-fashion open differentials, you need to go to VSC OFF MODE. This is when you stop moving, press and hold in the button until the VSC OFF light goes on.

To give the traction control of Auto LSD, TRAC OFF, etc. to Low Range, then there is the yellow wire or 4 Lo Trac MOD. Off Road Tacomas have A-TRAC, so that mod is not needed.

Here is one way to visualize the drive modes, 2012+:
Standard: TRAC (H2 or H4). A light limited slip.
Quick Push of Button: AUTO LSD (H2), TRAC OFF (H4). A stronger limited slip.
Stop and hold in button: VSC OFF (H2 or H4) for no Trac limited slip or stability control.

In Low Range 4WD, you are in VSC OFF only. Off Road TRDs have A-TRAC which is almost like having front and rear lockers but they lock automatically only when needed so steering is not hampered.

There is some question about Third Gens having TRAC in L4... ?

 

I am late to the party but here goes. The auto LSD is just a little more aggressive traction control without engine mitigating so you can spin the tires more. It's a great substitute for that occasional time when snow cover is not complete covering roads and 4 h might bind some. There are lots of times when you need temporarily slightly more traction that this feature gives you but not enough to warrant putting it in 4 wd. I have an OR and still use it frequently in 2 wd

With it not engaged, it's only the stability control that works and only when the tail starts spinning out. This is more aggressive so leaving it on too much would be hard on the rear brakes....just having traction control always engaged in a rwd lightly loaded truck would really over work the brakes too. It's ok with fwd cars, but not trucks.

Now, a real limited slip would be cool, but when it locks up, the rear can go crazy on ice and packed snow at higher speeds....a novice could easily leave the road. I like the compromise Toyota makes doing it this way, especially when my wife needs to drive it in slippery weather.

 

Are you trying to tell me my TRd sport has front and rear LSD and the TRD off road trucks only have a rear locker ??

 

every mode the sport has the trd OR also has, but in 4Lo the trd or ALSO has Atrac (even heavier brake simulated lsd/locker) and a true rear locker. Front and rear LSD is simulated via the brakes.

Also, auto LSD (2wd) and trac off (4hi) works SIGNIFICANTLY better on the TRD OR due do the much better all in one master cylinder / abs unit thats electrically boosted, vs the vacuum boosted systems on the non TRD OR 4x4 models (2009+ MY)