Lsd and alsd question

You know, its funny you say that. On a youtube comment for a TRD sport 4x4 I was checking out... a commenter said "I heard the trd sport 4x4 is really just a 4x2". What does this mean? That once a tire on each axle is spinning, you only have 2 left with traction? Last I checked a 4x4 is a 4x4.

Or he was just trolling saying it didn't have a locker? Still has the TRAC and auto lsd stuff.

 

Sometimes what you read in the manual or on the computer screen is hard to understand, it's honestly best to go out and experiment with your truck and learn what each system does and how it feels.

 

You're completely right. I was just saying its funny how someone said the 4x4 is really a 4x2. Makes no sense.

 

This mostly comes down to semantics. Couple things for clarity.

All limited slip functionality in Tacoma's short of the rear locker on TRD ORs/Pros is accomplished via brake actuation. We do not have mechanical limited slip differentials.

Auto LSD is one of the many available modes on Tacoma's. It is only available in 2WD and what it gives you is aggressive prevention of slip across the rear axle with zero throttle intervention. The result of this mode is very similar if not identical to that of a vehicle with a mechanical LSD and traction control turned off. I think the name is very confusing and I think it only exists for marketing purposes. It makes people think their Tacoma has an LSD and in effect it basically does, but technically it does not.

Outside of 2WD and ALSD, Tacoma's still use the brakes to accomplish LSD like functionality but it doesn't have a fancy name, it's just called traction control aka TRAC. ATRAC/MTS is a "boosted off-road oriented" version of TRAC.

Brake actuated LSD vs mechanical LSD...minimal difference for getting out of/through stuff. Now torque vectoring is an entirely different beast and in the realm of road circuit racing Toyota's implementation of LSD is abysmal at best. It is a sub-optimal implementation but for the intents and purposes of a Tacoma it does its job very well.

As far as Ram vs Tacoma traction....I really have no idea. I don't know what Dodge brings to the table as far as electronically controlled traction aids go. Toyota's brake actuated solutions are probably some of the best on the market, they have invested heavily in them.

Your friend is kidding himself if he actually thinks a dodge ram is better offroad than a Tacoma though...lol

 

haha thanks doggman. We were just bustin balls. He secretly loves my truck. So I guess an auto lsd isn't necessarily better or worse than a mech lsd. Also, any idea why someone would say a trd sport 4x4 is really a 4x2?

 

Sounds like he was just misinformed. He probably thought something like this...

Only TRD OR gets rear locker and ATRAC (locker for front) so non TRD OR is open differentials, which is true. 4x4 with open differentials can "turn into", if you will, 4x2 if you pick up a wheel on both axles, which is maybe fair enough. What he did not realize is Toyota's traction control system (TRAC) even on non TRD OR models will combat this. It is not as aggressive/effective as ATRAC/MTS but it will fight back so it's not at all the same as 4x2. I'd say it's more like 4x3.75 lol

 

Ooooops, I thought this was about drugs. Carry on!

 

You know you're about 40% waffling on your choice now if you keep this up, quit second guessing yourself and get ready for your truck to get here.

 

Ha! Wish the damn thing would just come in! But seriously, 4x2 just cuz no locker... c'mon. People are just misinformed

 

Got it. Now, if it was pure open diffs with no TRAC or TRAC OFF... he'd have more of a point. But then that would be calling all classic older 4x4 trucks without lsds or anything 4x2 as well. And with his logic... wouldn't the actual 4x2 be a 1wd?

 

I had a 2010 tundra and it had auto lsd, and it would roast both rear tires, with the traction control disabled and auto lsd active, especially if I killed the stability control too. Just like your buddy's ram would do.

 

I wrote this for you on Feb 22 here https://www.tacomaworld.com/goto/post?id=17214250#post-17214250
I think this fully explains it. Not trying to be repetitive, and obviously I think what I wrote for you has value, but read and re-read it a few times please if you want to understand the typical differentials, and what we have on 3rd gen. The sticky thread is still the go-to for modes of operation per trim. I also have a quick reference chart I wrote as part of 2wheel low mod that is very simplified, see attachments on https://www.tacomaworld.com/threads/lock-stock-and-2wheel-low-3rd-gen-diy-mod.536677/:

Several other well qualified people already answered you well, but I will try too. Lets see who can call me out for the inevitable errors.
Let's start with what the common differentials do when 1 wheel is off the ground
(To review without getting math heavy, Torque is rotational force (ie distance X force such as ft-lb) and Power is Torque x rotational speed, without getting into actual units)

Open Diff: Free wheel and grounded wheel take equal torque. Free wheel takes almost no torque to rotate, so ground wheel has almost no forward thrust. Free wheel has massive speed and grounded wheel has zero speed. Grounded wheel takes essentially zero power (Torque x rotational speed).

Mechanical limited slip Diff: There are many kinds of these, but generally a component in the differential attempts to limit the maximum speed mismatch between the two wheels. The free wheel must spin at a significant rate to create the speed differential that gives a torque differential. Clutch packs or viscous couplings generally add more torque to the grounded wheel and take it away from the free wheel. Significant tire speed differences are expected when operating at free condition. LSD systems will commonly wear out their clutch packs or viscous oils will require maintenance replacement over time. Some power lost to free wheel.

Simulated Limited Slip Diff: Again, many kinds, but generally the wheel brakes (using ABS sensors) apply braking to the high speed tire using a computer with a standard open differential. This braking increases the torque required to spin the free wheel. Because torque is equal across an open differential, this applies more torque to the grounded wheel. Some significant wheel speed difference is required to activate the computer and for it to detect with ABS sensors. Standard wheel brakes are used in the function and will have additional wear (but these items are normally used to stop the truck from 60 mph, so not a huge impact in the long run imho). Called TRAC, also A-TRAC and MTS/CC with differences on this vehicle. (TRAC is on all models 2hi and 4hi and sr/sport 4Lo. A-TRAC and MTS on OR/PRO on 4Lo only). Some power lost to free wheel.

Locked Diff: Wheel speed is locked across the axle, so the free wheel turns with the ground wheel, not spins. Torque is no longer the same across the axle at all. Torque on the free wheel is essentially zero and all applied torque goes to grounded wheel. Free wheel looses essentially no power (as it is at essentially zero torque.)

So open diffs torque same across axle (with torque at the wheel modified by brakes, surfaces, etc). Locked diffs speed same across axle (with torque varying)

So now that we talked about the main diff types, lets talk solely about what the 3rd gen has. All 4x4 3rd gen Tacomas have a center transfer case and open diff front and rear in normal usage (OR/Pro have differences in 4Lo). In 2wd and 4Hi for every one of the trims, unless you disable it, brake simulated LSD with physically open diffs will apply brakes to the spinning wheel(s). The center transfer case is NOT a differential as you have on AWD (all wheel drive) vehicles, and acts similar to a locked differential which is why 4hi and 4Lo are not to be used on dry pavement on this vehicle. For all trims except OR/Pro, in 4Lo the vehicle still has brake simulated LSD. For the OR/Pro, the rear differential can be locked (only in 4Lo). The OR/Pro also has ATRAC or MTS/CC, which is still brake simulated limited slip, but with a more powerful hydraulic brake master cylinder to apply more brake force to the free wheels.

All trims have essentially zero traction control differences in 2Hi and 4Hi. In 4Lo the OR/Pro adds a bit more capability and options with a rear locker and stronger Brake LSD.

Now just a little of history. Ignore this if it confuses you.
In 2nd gen, the SR/Sport/etc trims had no Brake LSD in 4Lo (just open diffs). There were workarounds. Now all trims have Brake LSD in 4Lo. All current trims (in 4x2 and 4x4) have much greater traction control than my old first gen with just open diffs. I might have bought an SR if I knew Brake LSD was also in 4Lo, instead bought OR. This is not well advertised.

So helpful?, probably not...

 

Awesome man, thanks for all the continued help. Think I'm finally getting this stuff now. The bolded part is a good argument for the sport guys when in the "sport vs OR" threads but I never heard it before!

 

damnit, I don't think i'm the only one who had a brain fart and came to this thread thinking we were going to be discussing our favorite psychedelics

 

If you don't get off the Web about the truck soon you'll be mis-informed.

 

The guy you were talking to was probably talking about a 4 wheel drive with an open diff in the front and rear.

 

Which all tacos are, only with brake assisted electronic slips, which he didn’t account for making his statement false. And if we went by his logic, that would make the actual 4x2 a 1wd lol.

 

Wow, great explanation! One quick question, whenever people talk about "turning on ATRAC", wether it be on here or youtube, they engage "Crawl Control". I rarely see anyone discuss MTS. I thought MTS was "adjustable ATRAC" and "Crawl Control" was simply cruise control for 4lo. So my question is, if you turn on Crawl Control without MTS, are you activating ATRAC?

 

Hey guys,

Just watched this video and it’s confusing the 4x4 knowledge I thought I had! Basically it’s saying in 4hi, if one wheel loses traction, then the vehicle stops. You then have to use a diff lock in the transfer case to make the wheels on the other axle move again. I thought in our 4x4s, if 1 wheel slips, the other axle still has power to the wheels. In other words, each axle is independent from one another.

https://youtu.be/-dh0VQxprJA

 

A-Trac is on Manual Trans Models and Crawl Control on Automatics