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UPDATE: Goto post #71 (found here Page 71 ) for an revise update if you don't wanna wade through all the info.

I know this topic has been discussed to death. Since many of us are new to wheelin, all of these terms can be very confusing. This info is easily located in the owner's manuel page 123-130 ish which i know most hesitated to read. I typed this out more for me to get these straighten out so I know when or when not to use them. If I misunderstood any of these concepts, then feel free to let me know. I posted this in another thread, but thought it deserved it's own.

TRAction Control system (pg 123). This is refering to TRAC. automatically helps prevent spinning of the rear wheels (2wd models) or 4 wheels (by adding brakes) when the vehicle is started or accelerated on slippery road surfaces.
Doesn't require push button activation. Works on it's own and is activated when the ignition is turned on. all FJ's have this whether 2 or 4wd model. On automatics, I am assuming this works in 2H or 4H, doesn't matter. If the system detects wheel spin, it adds brakes to increase traction.

A-TRAC is Active Traction Control system (pg 125) automatically helps prevent the spinning of 4 wheels when the vehicle is started or accelerated on slippery road surfaces. (basically same as TRAC, but only works in 4 Lo). To activated, hit the ATRAC switch, shift into Nuetral, and shift the 4x4 lever (short knob) into 4 LO. When in 4Lo, it detects wheel slippage and adds brakes accordingly to give added traction. Again, you must be in 4Lo and hit the "ATRAC" switch.

2wd models have Auto LSD (pg 127) instead of ATRAC. Automatic Limited Slip Differential uses the traction control system (TRAC) to control engine performance AND braking when one of the rear wheels begins to spin (or slip). This gives added traction to the vehicle.
Auto LSD has it's own button, found in the upper left hand corner of the buttons (found in 2wd models only). Apparrently it must be engage with the push of the "auto LSD" button when you're on a slippery surface (snow, ice, or lots o' water).
This is the 2wd's version of ATRAC found on 4wd models.

VSC (vehicle stability control) system on pg 130: integrates the control of the systems such as ABS, TRACtion control, engine control, etc to prevent the vehicle from skidding when cornering on a slippery road surface or operating steering wheel abruptly.
VSC is activated when the FJ reachs 9mph or 15km/h.
*VSC automatically turns off (VSC off light on dash comes on) when 4H/HL or 4Lo/LL is activated (AT/MT) or when the Rear Diff is locked.

Here's the conclusion....

-Both 2wd and 4wd models have VSC and TRAC. activated when FJ is started(TRAC) or when FJ reaches 9mph (VSC) and works when it's needed. No action required on your part.
-2WD models: when in snow, ice, or water, oil or anything slippery and you need a little extra traction control. Hit the Auto LSD to get added traction in the rear wheels.
-4WD models: TRAC works in 2H or 4H. when running 4 LO in slippery conditions such as snow, ice, water, oil, mud, slicks, etc. Hit ATRAC switch for added traction.

Rear Differential Lock System: for use only when wheel spinning (as oppose to wheel slipping) occurs in a ditch or on a slippery or ragged surface. Rear diff lock is effective when one of the rear wheels is spinning.
Note: use ATRAC when there is wheel slippage or partial traction.
Use RR Diff locker when there is wheel spinning or NO traction.
-Must be in LL (MT) or 4Lo (Automatics). It is also suggested that you try the LL or 4Lo 1st, it this is not enough, then activate the Rear Diff locker.
-Also mentions that a large steering effort and careful cornering is required. Means that you'll have a hard time steering, will seem very stiff.
Note: when using the rear locker the following systems do not work and their lights will come on (ABS warning light, VSC off light, and the slip indicator [ the car icon with double SS under the tires] light will ALL come on).

Well...clear as mud? Thanks for reading.

PS: going on a LONG drive tomorrow...all the way to Fresno.
 

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Thanks for an outstanding and extremely informative post, Tranman!:clap: You get come reputation points from me for that one! :cheers:
 

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I will add my praise to the discussion, as I have been trying to do my own research and reading since I am a newb to four wheeling. One thing that confuses me in the manual is comments on the A-TRAC system. The manual begins explanation on p. 125 of the A-TRAC system, however, the best I can tell, it is still discussing the A-TRAC system when you turn the page to 126. This is where I am confused as to quote from the manual, "Leave the system on during the ordinary driving so that it can operate when needed." When I read this, it read as if it were referring to the A-TRAC system, and yet on the previous page it says to switch to four wheel low. Anyone able to clarify my confusion here?
 

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Thanks for the summary....but for me its information overload. WIll print it out and put in my glove box just in case I need to look up real quick....
 

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Yes, great summary, BUT, there's still no real significant difference in any of the control systems (diff lock excluded). TRAC, ATRAC, and VSC all use the brakes to control wheelspin. So what if one only works in 2wd and one only works in 4lo, or if you have to push a switch to make you think you're stimulating the magic traction fairies, it's still performing the same function. The only difference is the computer programming logic involved.

"TRAC - If the system detects wheel spin, it adds brakes to increase traction."
"ATRAC - detects wheel slippage and adds brakes accordingly to give added traction"
"ALSD - uses the traction control system (TRAC) to control engine performance AND braking when one of the rear wheels begins to spin (or slip). "
"VSC - prevent the vehicle from skidding when cornering on a slippery road surface or operating steering wheel abruptly"

Does anyone see any real difference here? I just want someone to admit that it is one system that performs these functions. It's all the same computer, the same abs sensors, the same brakes. The abs sensors are used to detect wheel slippage, and then the brakes are applied individually as needed. The ALSD says it also controls engine performance, though I don't see why that function would be labeled ALSD, as it really should be part of TRAC. And then VSC is to prevent doing 360s around a corner, as opposed to the other systems that are designed for assistance with forward acceleration. BUT, even the VSC is detecting a loss of traction and applying brakes to individual wheels.

"RRDIFF - for use only when wheel spinning (as oppose to wheel slipping)"
There is no difference in slipping and spinning, so long as you're referring to forward acceleration (as opposed to braking). And how could one wheel ever spin anyway, with TRAC always active?

"Hit the Auto LSD to get added traction in the rear wheels."
So the TRAC only gives you a little extra traction, but ALSD applies the brakes a little harder? I don't get it.

"Hit ATRAC switch for added traction."
Again, added traction?

I know you didn't make this stuff up Tran, I'm not blaming you, but you have to admit it's baloney. That's why you can buy a $40 ATRAC switch to "unleash" this magic. Imagine how much money they've made by getting people to buy the upgrade package just for the ATRAC.


Customer: Why do I want this package?
Dealer: It has ATRAC!
C: It has an 8-track?!
D: No, AAAAA TRAC.
C: Aww that sucks, I have some old 8 track tapes at home that would sound great on the FJammer.
D: (fake chuckle)
C: So what is ATRAC?
D: It's a traction control system that controls wheel slippage in adverse conditions.
C: Oh. Doesn't it already have that standard?
D: No. That's TRAC.
C: So what's the difference?
D: Well, that's TRAC, this is AAAAA TRAC!
C: So the A makes it better?
D: Well it's more than just an A sir. See, it controls the wheel spin when you're in the 4wd low gear.
C: And TRAC doesn't do that?
D: Well it does, but it's different.
C: How?
D: Well, ATRAC only works in 4lo.
C: And TRAC doesn't?
D: Yes TRAC works all the time.
C: So TRAC also works in 4lo.
D: Well yes.
C: So why do I want ATRAC?
D: Because it's better.
C: And you can only get ATRAC in the 4wd? What if I wanted 2wd?
D: Well you can get Auto LSD.
C: 8 tracks, LSD, what's going on here?
D: (another fake chuckle) Not that kind of LSD sir. It stands for Limited Slip Differential.
C: What's that?
D: It's actually a simulated LSD, it uses the brakes to control wheel spin.
C: I thought that's what TRAC does.
D: It does, but TRAC is on all the time. You have to push a button to use ALSD.
C: Hmm. You people are proud of your buttons aren't you. So back to the ATRAC, how do I turn it on?
D: You push this little button right here.
C: And how can I tell it's working?
D: There's a light on the button.
C: Oh, a light. Well that's pretty cool. Alright, I'll take it. And how much extra is this package?
D: It's just a little bit more, we'll make the numbers work. Let's go sign those papers... (as they walk off into the sunset)
 

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Discussion Starter · #8 ·
Thanks for the responses and reputation points. Just wanted all to know that tho I post frequently, I am not a wheeler. I have very little experience when it comes to this off roadin stuff. I learning just like the rest of us. I plan on doing light trails and progressing slowly. Haven't even used some of these systems yet.

Ridge111 said:
I know you didn't make this stuff up Tran, I'm not blaming you, but you have to admit it's baloney. That's why you can buy a $40 ATRAC switch to "unleash" this magic. Imagine how much money they've made by getting people to buy the upgrade package just for the ATRAC.
You're right, I didn't make it up. Just what I gathered from reading and just tried to make some sense of it myself. I could be totally wrong. I haven't used any of these systems in real world applications other than playing with them briefly.
Just thought I would shared my interpretation of the material.

Hear ya on the atrac switch as well. I would say most who got the package probably wanted the other items too. Just imagine dealerships also made $4K plus on each of just who bought at MSRP!

Ridge111 said:
Yes, great summary, BUT, there's still no real significant difference in any of the control systems (diff lock excluded). TRAC, ATRAC, and VSC all use the brakes to control wheelspin. So what if one only works in 2wd and one only works in 4lo, or if you have to push a switch to make you think you're stimulating the magic traction fairies, it's still performing the same function. The only difference is the computer programming logic involved.

"TRAC - If the system detects wheel spin, it adds brakes to increase traction."
"ATRAC - detects wheel slippage and adds brakes accordingly to give added traction"
"ALSD - uses the traction control system (TRAC) to control engine performance AND braking when one of the rear wheels begins to spin (or slip). "
"VSC - prevent the vehicle from skidding when cornering on a slippery road surface or operating steering wheel abruptly"
I agree with you. when I first read it, I thought all were the same, especially TRAC and VSC. I bet some of the more techinically minded members know the differences and the exact applications. (RoverGGM, KLD, Percy, Thai, there's more of you out there, please chime in)

Ridge, by added traction, I meant added torque not added braking. I don't fully understand these issues myself so I can't competently and completely answer your questions.

Sounds like the difference b/t TRAC and ATRAC is not much. One works for normal driving and one for 4LO. Same system, slightly different application.
Sounds like ASLD is similar to ATRAC except it is for 2WD models and only works in the rear wheels. It is probably the same, but again works only in the rear wheels. VSC incorporates ABS, traction control, and manipulates engine performace to give your more control of the vehicles for turning. A different application than TRAC, ALSD, or ATRAC - all for wheel slippage.

The real world difference b/t TRAC and ATRAC. All I can say is go out and get yourself stuck and see if ATRAC makes a difference over TRAC or not. Some say it does make a BIG difference. I think when you are in 4Lo, TRAC is not active. I'm not 100% about this one tho. If that is true, then ATRAC (in 4 LO) would replace TRAC. Why didn't they just make it automatic instead of us having to depress a switch?

I'm guessing b/c sometimes you want RR diff lock and sometimes you want ATRAC (again different applications). You can't run them both at the same time. Why? I don't know but this one's been hotly debated again and again.
Anyways if you find the answers, post them up. I'd like to know as well. Cheers, Tran:eek:rangehat:
 

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Although these systems use the same basic components, they use different parameters and sensors to affect their function. For example, VSC uses a yaw sensor to detect angular momentum to calculate which brakes to apply and what direction the skid is likely to occur. The speed they come into play is different, as you wont be going more than 10-15 mph in 4lo, while you could be at freeway speeds in 2hi. Hope that helps...:roller:
 

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I know that the manual says to reduce speed to 50mph to shift from 2H to 4H (in automatics), but if you are driving in wet or snowy conditions on a highway is there limit to "safe" speed in 4H mode. Obviously, the conditions of the road stipulate to a great extent what is a safe speed, but what is safe for the 4H operation of the engine. The other night when driving home, we ran into a heavy downpour with puddling on the highway, and I was concerned about how fast I should/could go with 4H active?
 

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tjpyles said:
I know that the manual says to reduce speed to 50mph to shift from 2H to 4H (in automatics), but if you are driving in wet or snowy conditions on a highway is there limit to "safe" speed in 4H mode. Obviously, the conditions of the road stipulate to a great extent what is a safe speed, but what is safe for the 4H operation of the engine. The other night when driving home, we ran into a heavy downpour with puddling on the highway, and I was concerned about how fast I should/could go with 4H active?
You should NEVER drive in 4H above the max speed.

Hell, I wouldn't go over 40.

That system isn't designed to be operated at such speeds off or on-road--regardless of the conditions.
 

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Thanks for the great writeup.

At the dealership I knew something was up when I was being sold ATRAC as THE traction control system on the manual implying without UR the FJC had NO traction control system. I was thinking "if it is a full time four wheel drive and doesn't have any means of detecting wheel slippage (mechanical or electronic) to direct power from slip wheels to grip wheels what's the point of a full time 4wd system?" I knew something was afoot.

Now the question I have left is...

Is there a way to turn off any and all systems that would use breaks to transfer power? ...allowing wheel slippage and unadulterated winter fun? From your writeup it appears there is no way.

In my current car, a Volvo v70R (300hp, AWD) I run Dunlop Winter Sport M3 for snow tires and can turn off "Dynamic Stability and Traction Control" by pushing the DSTC button five times. I can get a nice roostertail of snow and slide the backend out around a snowy corner. With the system on the brakes kick in and the engine revs down before the fun starts.

[edit: I searched and found my answer. :mecry: ]

Thanks,

--booboo
 

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I just wish you didn't have to be in 4L to operate the diff lock. Sometimes I just want to be in 2WD and do doughnuts:rocker:
 

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tjpyles said:
I know that the manual says to reduce speed to 50mph to shift from 2H to 4H (in automatics), but if you are driving in wet or snowy conditions on a highway is there limit to "safe" speed in 4H mode. Obviously, the conditions of the road stipulate to a great extent what is a safe speed, but what is safe for the 4H operation of the engine. The other night when driving home, we ran into a heavy downpour with puddling on the highway, and I was concerned about how fast I should/could go with 4H active?
I don't know that you really need to be in 4H just for wet roads. Think about all those 2wd cars driving around just fine in the rain. Snow is a different story, but if it's only rain, IMO, I'd keep it in 2H.
 

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tjpyles said:
I know that the manual says to reduce speed to 50mph to shift from 2H to 4H (in automatics), but if you are driving in wet or snowy conditions on a highway is there limit to "safe" speed in 4H mode. Obviously, the conditions of the road stipulate to a great extent what is a safe speed, but what is safe for the 4H operation of the engine. The other night when driving home, we ran into a heavy downpour with puddling on the highway, and I was concerned about how fast I should/could go with 4H active?
How fast would you like to go in snowy / wet road conditions ?? I'd venture to guess the 4H transfer case will put up with higher speeds (it does in my other vehicles), but really, I'd recommend caution with your speed if your concerned enough to use 4h to make it through...JMO..:worried:
 
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Landrover said:
I just wish you didn't have to be in 4L to operate the diff lock. Sometimes I just want to be in 2WD and do doughnuts:rocker:
Alocking diff will prevent doughnuts, not assist them - you need an open differential to get one wheel to overpower the other for a doughnut, unless you're on wet / icy pavement...:cowfrown:
 

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Discussion Starter · #17 ·
Landrover said:
I just wish you didn't have to be in 4L to operate the diff lock. Sometimes I just want to be in 2WD and do doughnuts:rocker:

FYI, Percy previously posted a link to a TTORA that gives instructions on how to hack this so that you can use the rear diff lock while in 2 wheel. He also said he was waiting for his warranty to run out before doing this himself.

OK found it....
Percy said:
Tranman - The mod for the rear locker has been figured out. You can do a search on TTORA and there is actually a very good write up. It is similar to the grey wire mod on older toyota 4x4's, but requires the installation of a DPDT 20 amp relay. This will allow you to lock the rear no matter what transfer setting you are at. I plan to do this to my 06 Taco, but not until it's out of warranty.
 

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JLam said:
I don't know that you really need to be in 4H just for wet roads. Think about all those 2wd cars driving around just fine in the rain. Snow is a different story, but if it's only rain, IMO, I'd keep it in 2H.
Agreed. In rain you want your VSC working for better vehicle control. The VSC is turned off when you go into 4WD.
It's all about control of the vehicle.
ATRAC is similar to TRAC. ATRAC available in 4WD and TRAC in 2WD, but sometimes in 4WD you want the ability to turn it off (like sand when you want the tire spin), so there is a button to do so. There is not a button to turn off TRAC while in 2wd as you always want that assistance while you are driving to the mall on a rainy day.

At the risk of repeating myself, all of this was designed for vehicle control, not for donuts and not for drifting. :D
 

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The big distinction between TRAC and ATRAC is that ATRAC is a traction assist while allowing full engine power to be provided.

TRAC works when it senses slippage (such as on snow) to apply pulse braking to the slipping (spinning) wheel and cut engine power for driving control. Because TRAC works in both high and low ranges, when higher speeds are probable, cutting engine power is a safety feature.

The reason ATRAC is limited to 4WD Low Range is because it is an aggressive traction control. When negotiating a rough section of trail where a wheel losses traction, through suspension articulation (one wheel lightly touching the ground) or wet slippage, you don't want the engine to cut power to correct the consequences of traction loss. You just want the slipping wheel to stop spinning. The engine torque is required and cutting power would defeat the effort to overcome the obstacle.
 
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What KLD said...ATRAC is a more aggressive form of TRAC. ATRAC does not cut engine power and it will brake the spinning/slipping wheel quicker and more aggressively...it is for off-roading only or for slow speed traction.

For example, TRAC slows down the spinning/slipping wheels. This is good in all-weather driving in which you do not want ABS brakes to stop a wheel completely...this may create instability on-road. ATRAC, on the other hand, is for off-roading only. Thus, it can actually stop the spinning wheel altogether for a short period of time (aka brake the spinning wheel to zero mph). This allows for more efficient transfer of torque to the other wheel with traction.

Here is a thread i wrote a long time ago about ATRAC and torque transfers: http://www.toyota-4runner.org/showthread.php?s=&threadid=5036

VSC is for stability to prevent oversteer and understeer. In theory, it has very little to do with straight line traction (this is where TRAC comes in). VSC is to save your ass if your car loses control on an off-ramp for example.

Auto LSD is another BS term Toyota uses to describe traction control. Marketing term.

Although (A)TRAC and LSD are two different thing, they FUNCTION (in practical terms) similarly...aka, they help your FJC move forward over poor traction surfaces. Therefore, auto manufacturers (not just Toyota) are using these terms interchangeably to confuse consumers into thinking that their car has some new advance technology, when this technology has been on cars since the late 90's in Land Rover Discovery and Mercedes ML.

Rear locker locks the rear axle together into one solid rod...it ties the rear wheels together as if it was one wheel. One rear wheel turns...the other MUST too. Unlike ATRAC, rear locker binds if you make a turn on high traction surfaces (pavement). ATRAC is more flexible because it causes much less binding.
 
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