The difference between TRAC and AUTO LSD

Yes, I have read several "drive modes explained" threads, including the YWM etc etc. And yes, I have read my owners manual, and yes, I am still confused.

According to the 2012 Tacoma owner's manual the: TRAC system

-"Helps to maintain drive power and prevent the drive wheels from spinning when starting the vehicle or accelerating on slippery roads."

I understand this as saying that it affects all four wheels when in 4wd mode.

According to the same manual:

-"The AUTO LSD system aids traction by using the traction control system to control engine performance and braking when one of the rear wheels begins to spin"

To me this reads that obviously it only affects the rear wheels. What is the "traction control system" that it uses to do this, the TRAC system?

From all of this I gather that the only difference between TRAC and AUTO LSD is that AUTO LSD is for the rear wheels only...am I way off?

As an aside what exactly does the VSC system do, how does it do it, and how does it affect the other driving modes?

Sorry for so many questions, this is still not clear to me after days of research and reading. Thank you.

Here is what Toyta Tech support had to say about this...

"Vehicle Stability Control (VSC):​

Part of the Star Safety System™ standard on all Toyotas, this feature interprets data from a steering wheel position sensor and the ABS wheel-speed sensors to determine if the vehicle is following the driver’s intended path. If the vehicle is deviating from the direction in which the driver is steering, VSC is designed to reduce engine power and pulse the left- or right-side brakes to help correct the situation.

Traction Control (TRAC),
By interpreting data from the ABS wheel-speed sensors, TRAC can tell if a drive wheel is turning faster than a non-drive wheel, which indicates loss of traction. When TRAC detects slippage, the system can automatically reduce engine power until the wheel that is slipping slows and regains traction. If reducing engine power isn’t enough, the braking system will gradually slow that wheel through pulsed brake action.

Automatic Limited Slip Differential (Auto LSD)
It is a second-level, low-speed traction control feature on some 2-wheel-drive (2WD) trucks and SUVs. The first level, Traction Control, is designed to reduce drive-wheel spin. The key difference in the activation of Auto LSD is that, along with brake application to a spinning wheel (which helps engage a non-spinning wheel), Auto LSD also allows engine power to spin the drive wheels faster than the non-drive wheels. This comes in handy on boat ramps and when driving in modest off-road terrain, where some wheel slippage is desired."

 

This is probably one of the threads you've already read, but if you read through all of David K's posts it explains everything for 2009 through 2011 models.

http://www.tacomaworld.com/forum/te...uto-lsd-explained-easy-understand-i-hope.html

We've found that some vehicle behavior and wording in the manual changed in 2012, and I don't think any of us has a complete understanding of it yet. I'm sure David would but he doesn't have a 2012 available to play with.

I'd like to completely understand my 2012 but I still have a way to go. Since you asked about VSC I'll give you an example of how some of it works. We have some new roundabouts near where I work. I tend to drive a little assertively sometimes, and when the roundabouts were new I'd see how fast I could take them within reason. Road speed limit is 35 MPH and you're supposed to slow to 15 MPH while in the roundabout. When I try to take the turn at 30 MPH or so the VSC cuts my throttle because the yaw sensor detects that I'm generating too much lateral G force. Even though I'm in complete control and could even be performing a critical evasive maneuver, the VSC takes over and my fate is in Toyota's control. For most drivers that's probably a good thing. Another example happened this Spring when there was a lot of sand at intersections left over from Winter. I'd take a left turn pretty fast and the rear tires started spinning on the sand, but I'm still in complete control. Suddenly the front left tire is braking and the engine power cuts. Once again VSC has saved some idiot from losing control, and prevented me from being in control. Toyota has a nice video of how it works and it is a good safety system

Another plus side to it taking control is the traction modes you're asking about. It uses those same brake and throttle controls to make your vehicle get traction in places where you could not without a locker or mechanical LSD.

I guess I rambled a bit, hope that helps some.

 

So TRAC and AUTO LSD are modes of VSC?

 

VSC is on as default. Basically it's suppose to keep you going straight if you begin to fish tail and also regulates the engine. it will bog down if too much wheel spin is going on.

Pushing your button once turns on auto LSD. Now the engine is not regulated allowing for straight forward wheel spin. It manages which rear tire has power to keep you going up a slippery surface. I believe VSC is still in use to prevent fish tailing at this point.

Push and hold the button for about 3 seconds and it turns everything off. It's like having a 90's Toyota pickup. You can go blow donuts with no engine or drivetrain regulation.

I don't remember which is on during 4wd engagement.

 

How is the VSC still in use if you say the engine is not regulated anymore?

You can see where my confusion is coming from...

 

1. VSC is on unless you turn it off and it uses brakes on all 4 wheels and throttle regulation to keep the truck under control (stability control). This is true in 2wd and 4-HI.

2. Pressing the VSC button, disables VSC and enables TRAC/Auto-LSD (no throttle regulation). This will not prevent fishtailing but does use brakes to improve traction. In 2wd, only the rear brakes are used.

3. When operating in 4-HI, VSC operates the same as 2wd. However, if you press the VSC button to disable VSC in 4-HI, you now have TRAC/Auto-LSD on both your front and rear axles that uses the brakes but no throttle regulation. The traction control (brakes) on the front and rear work independently of each other to improve traction.

4. When operating in 4-LO, you have no VSC or TRAC/Auto-LSD available unless you have a TRD Offroad package. YWM gives you TRAC in 4-LO.

Summary: VSC is on unless you turn it off and it will regulate engine output. The throttle will only be regulated if VSC is on. Once you turn off VSC and enable TRAC/Auto-LSD, the system will use brakes on the rear for 2wd and on front/rear for 4-HI to improve traction. As previously mentioned, if you hold down the VSC button for a few seconds, you disable VSC and TRAC leaving you with truly open differentials and no throttle regulation.

Hope that helps.

 

This is right from my owners manual.

TRAC: Maintains drive power and prevents the rear wheels or 4 wheels from spinning when starting the vehicle or accelerating on slippery roads.

VSC: Helps the driver to control skidding when swerving suddenly or turning on slippery road surfaces.

TO DISABLE TRAC: Quickly push and release the VSC Off switch to turn off TRAC.

TO DISABLE TRAC and VSC: Press and hold the VSC Off switch for more than 3 seconds while the vehicle is stopped to turn off both TRAC and VSC.

 

VSC - brakes one or more wheels to maintain directional control. For example, when turning a corner too fast and the rear end steps out (oversteer), VSC will bring it back in line. You hear a chime when it kicks in.

TRAC - works mostly in a straight line. When accelerating from a stop, if a tire spins, the engine throttle back to reduce power.

Auto LSD - works mostly in a straight line. When accelerating from a stop, if a tire spins, the brake engages on that wheel (which sends torque to the opposite wheel). The engine is not throttled back.

 

This what I needed, thank you!

 

Good info!

 

From the other threads: it shows here that engine output is not regulated with TRAC.

I think you have TRAC and AUTO LSD mixed up...

 

You said:
From the other threads: it shows here that engine output is not regulated with TRAC.

NOT CORRECT> If you want to get a handle on the terminology and how
it works you need to be accurate in your statements and questions. it is
not rocket science, but you are not helping by putting up incorrect info.

Incorrect: it shows here that engine output is not regulated with TRAC.
Corrected: it shows here that engine output is not regulated with TRAC when in 4wd, and it is regulated when in 2wd.

You see, the only way to really discuss this is provide ALL details and
expressly define which of the 9 possible modes you are talking about...and
do not assume or skip anything. it is right in the picture you posted.

The bottom line is:

All 4 wheels have independent computer braking, that the computer handles.
And...the system cuts power or doesn't cut power, in specific modes and situations

It all uses the same computer, it just runs a different algorithm depending on your
switches and transfer case settings.

The 2wd auto-lsd on these things is brilliant. I am using 4wd less and less when I do not
need crawl gears...the auto lsd only allows slips about 1/8th<>1/16th rotation and boom, I am rolling.
These Toyota traction systems are all business.

 

Let me see if I have this figured out...

VSC= Brake control with engine output regulation all 4 wheels. No operation in 4lo.
AUTO LSD= Brake control for REAR wheels only with engine output regulation only in 2wd. No operation in 4lo.
TRAC= Brake control and engine output regulation in 2wd, brake control without engine output regulation in 4hi. No operation in 4lo.

It seems as though in 2wd AUTO LSD, TRAC, and VSC perform the exact same functions?

 

The person I was replying to made the same mistake. No biggie. I guess it is not really rocket science, but 15 people are saying 15 different things that contradict each other. Just because you think you have a grasp on something doesnt really mean you do. Im the one trying to figure this out here, not explain something incorrectly to someone else...

 

^^^ I am not trying to be a dick, I solve technical problems for a living and have a hard
time understanding how this can be misunderstood
---
It seems as though in 2wd AUTO LSD, TRAC, and VSC perform the exact same functions?

Yes ^^^ but no: they all apply brakes, so in that regard, yes. But they will only
do it in certain patterns and conditions depending on what button you have pressed

VSC is entirely different (it is still brake and throttle control), but
this is to stop sine-wave fishtailing on the highway when or if you
end up over correcting for dodging a deer or obstacle. it will kick in
anytime it is allowed and anytime you start to get sideways

 

Thanks, here is what I got from Toyota tech support. Give us a little more in depth as to exactly what the different modes do!

​

Vehicle Stability Control (VSC):​

Part of the Star Safety System™ standard on all Toyotas, this feature interprets data from a steering wheel position sensor and the ABS wheel-speed sensors to determine if the vehicle is following the driver’s intended path. If the vehicle is deviating from the direction in which the driver is steering, VSC is designed to reduce engine power and pulse the left- or right-side brakes to help correct the situation.

Traction Control (TRAC),
By interpreting data from the ABS wheel-speed sensors, TRAC can tell if a drive wheel is turning faster than a non-drive wheel, which indicates loss of traction. When TRAC detects slippage, the system can automatically reduce engine power until the wheel that is slipping slows and regains traction. If reducing engine power isn’t enough, the braking system will gradually slow that wheel through pulsed brake action.

Automatic Limited Slip Differential (Auto LSD)
It is a second-level, low-speed traction control feature on some 2-wheel-drive (2WD) trucks and SUVs. The first level, Traction Control, is designed to reduce drive-wheel spin. The key difference in the activation of Auto LSD is that, along with brake application to a spinning wheel (which helps engage a non-spinning wheel), Auto LSD also allows engine power to spin the drive wheels faster than the non-drive wheels. This comes in handy on boat ramps and when driving in modest off-road terrain, where some wheel slippage is desired.

 

VSC = stability control
LSD = launch control
TRAC = traction control
ATRAC = very strong traction control at low speed

 

Modest off-road terrain? That's a term that needs some definition!

Unfortunately I haven't had the need to use AutoLSD, even in the snow; just standard 2wd.

 

I am really trying to get a handle on this,

I was however out on a country road we have here in the mountains near Asheville, it's regularly populated with campers and hikers and the like, Usually I am on it once a month as the trip from one end to another is kind of a loop, Bent Creek up to the parkway and then back down the mountain to Mills River, I use it to be sure and get the FWD portion of my 4WD lubed up good per my owners manual, Lol...

I started playing with the button, and have found when just tooling around in 2WD and I turn TRAC off, "one push" the AUTO LSD light comes on, it works very well for getting my little truck up the moderate gravel roads without a lot of axle hop and such.

I am actually impressed,

I was wrong and didn't realize that a shift into 4WD Hi also has the AUTO LSD at both front and rear,

and now understand if I needed to "rock" my Tacoma in a stuck situation I would hold the button down while stopped and then my AUTO LSD would be turned off with the VSA,

I can see where I may want this YWM on a SPST switch for 4WD Lo and AUTO LSD if we get some good snow this winter.

I mean if your tooling around in 4Lo your probably going to need the ability to get all the power you can to the wheel with traction, and the ability to do this easily with a switch is great.

Thanks to all who came up with this and dove into the wiring details and such,

I appreciate the help and your wanting to make driving my Tacoma an even better experience than it already is,