Can someone explain why the '01-02 "Active" Trac is bad?

[Lindenwood]

I have heard lots of "it sucks!" anecdotes, but despite reading pretty much every thread (on this forum and other offroad forums) connecting this model 4runner with "Atrac," I havent found any actual explanation for why it would actually be detrimental to offroad capability.

To clarify, I am not talking about the annoyance of having the VSC preventing powerslides in the snow and mud. Also, assume I am talking exclusively about wheeling with the center diff locked (i.e. VSC not active).

Also, just to clarify what I mean by "ATrac," and differentiate it from VSC, I'll quote the manual from the manual:

Traction control system (two–wheel drive models)
The traction control system automatical- ly helps prevent the spinning of rear wheels when the vehicle is started or accelerated on slippery road surfaces.
...
If your wheels get stuck in an ditch when you are driving on a severe off road and sand, turn off the traction control system. This system that con- trols engine performance interferes with the process of freeing the wheels.

Active traction control system (four–wheel drive models)

The active traction control system auto- matically helps prevent the spinning of 4 wheels (four–wheel drive mode) or rear wheels (two–wheel drive mode) when the vehicle is started or acceler- ated on slippery road surfaces.

Vehicle skid control system (four–wheel drive models)
The vehicle skid control system helps provide integrated control of the sys- tems such as anti–lock brakes, traction control, engine control, etc. This sys- tem automatically controls the output of the brakes or engine to help prevent the vehicle from skidding when corner- ing on a slippery road surface or oper- ating steering wheel abruptly.
...
If your wheels get stuck in a ditch or when you are driving on severe off road and sand, turn off the vehicle skid control system. This system that con- trols engine performance interferes with the process of freeing your wheels.
To turn off: Push the center differential lock switch.

That is, ATrac only using the ABS system to apply brakes. The Vehicle Stability Control system uses both engine dethrottling and the ABS system to prevent slides.

Anyways, I am just looking for more illumination beyond "it sucks." Why, specifically, does it suck?

 

[psraff]

I have heard lots of "it sucks!" anecdotes, but despite reading pretty much every thread (on this forum and other offroad forums) connecting this model 4runner with "Atrac," I havent found any actual explanation for why it would actually be detrimental to offroad capability.

To clarify, I am not talking about the annoyance of having the VSC preventing powerslides in the snow and mud. Also, assume I am talking exclusively about wheeling with the center diff locked (i.e. VSC not active).

Also, just to clarify what I mean by "ATrac," and differentiate it from VSC, I'll quote the manual from the manual:





Anyways, I am just looking for more illumination beyond "it sucks." Why, specifically, does it suck?

Just buy a '99 and don't worry about it. LOL Really though... I just saw a thread just two or three pages back that explained this in detail. Sorry, don't have the link on me right now, but it wasn't that old. Maybe just browse the pages and you can come across it.

I'm sure someone else has seen it also...

 

[JayRolla]

I have heard lots of "it sucks!" anecdotes, but despite reading pretty much every thread (on this forum and other offroad forums) connecting this model 4runner with "Atrac," I havent found any actual explanation for why it would actually be detrimental to offroad capability.

To clarify, I am not talking about the annoyance of having the VSC preventing powerslides in the snow and mud. Also, assume I am talking exclusively about wheeling with the center diff locked (i.e. VSC not active).

Also, just to clarify what I mean by "ATrac," and differentiate it from VSC, I'll quote the manual from the manual:





Anyways, I am just looking for more illumination beyond "it sucks." Why, specifically, does it suck?

It sounds like it should work really good right? I dont have it buy my brother does in his 4th gen and from what I understand it works just like a 3rd gen and maybe a bit better.

I told him about the andy mod to disable it and he quickly found out why people do. In mud or deep snow and you hit the gas the tires spin. The traction control uses the brakes to slow the wheels until they grip. Issue is the car starts to slow so much and you keep hitting the gas but car keep slowing. If the mud or snow is deep enough you will literally be stopped and get stuck because traction control robbed you of all power.

Another issue is if your climbing a hill and start sliding the motor loses all power and you cant even get it to climb anymore getting stuck in a very bad spot sometimes.

Last but not least you also are not able to do donuts or power slide when you want. It just stops the vehicle pretty much. That was his last draw and he added switch to disable it.

I'll add it works good on street with icy/wet roads. Good to keep enabled on the street.

 

[Lindenwood]

Thanks for the responses!

I do understand the principles behind the ATrac system. I also have a 5th gen TRD Pro, which uses its ATrac system to great benefit. In fact, the ATrac system is one of several reasons I chose my 2002. I understand my TRDP's ATrac is both more refined and also tuneable, but the baseline function should be the same.

It sounds like it should work really good right? I dont have it buy my brother does in his 4th gen and from what I understand it works just like a 3rd gen and maybe a bit better.

I told him about the andy mod to disable it and he quickly found out why people do. In mud or deep snow and you hit the gas the tires spin. The traction control uses the brakes to slow the wheels until they grip. Issue is the car starts to slow so much and you keep hitting the gas but car keep slowing. If the mud or snow is deep enough you will literally be stopped and get stuck because traction control robbed you of all power.

Another issue is if your climbing a hill and start sliding the motor loses all power and you cant even get it to climb anymore getting stuck in a very bad spot sometimes.

Last but not least you also are not able to do donuts or power slide when you want. It just stops the vehicle pretty much. That was his last draw and he added switch to disable it.

Are you sure he wasn't mistaking the increased wheel resistance that results from corrective braking for dethrottling? The Atrac system doesnt reduce engine power to correct wheel spinning. If one wheel has minimal traction and starts to spin up, the engine RPMs will increase as it is allowed to rev more freely if throttle is not reduced. If the ATrac system then applies the brake to that spinning wheel to transfer the available power to the static wheel, the engine RPM will decrease as the load increases, which might be misconstrued as dethrottling.

Or, are you saying the system is so poorly calibrated that it will apply brakes to both wheels on the same axle?

Also, I have read that past certain throttle inputs and / or RPMs, the ATrac minimizes or ceases its interference. Can anyone speak to that?

As to the system preventing donuts and power slides, that is actually a function of the VSC, and not ATrac. That said, I am not concerned enough about the VSC preventing donuts and slides to disable it for the time being. If I really wanted to play in the ice and snow, I would just lock the center diff.

 

[Unner]

I think it's a good thing to have. VSC can keep you safer on the streets in an emergency maneuver, and it gets turned off offroad when the CDL is locked. The only system on then is Trac which can help "simulate" a locker or LSD sorta if you don't have one by applying brakes to the spinning wheel.

I've had my VSC kick in on the interstate during a torrential southern Mississippi downpour and a HARD emergency braking event. It helped straighten me back out and keep me from going into the center median sideways.

 

[JayRolla]

Thanks for the responses!

I do understand the principles behind the ATrac system. I also have a 5th gen TRD Pro, which uses its ATrac system to great benefit. In fact, the ATrac system is one of several reasons I chose my 2002. I understand my TRDP's ATrac is both more refined and also tuneable, but the baseline function should be the same.



Are you sure he wasn't mistaking the increased wheel resistance that results from corrective braking for dethrottling? The Atrac system doesnt reduce engine power to correct wheel spinning. If one wheel has minimal traction and starts to spin up, the engine RPMs will increase as it is allowed to rev more freely if throttle is not reduced. If the ATrac system then applies the brake to that spinning wheel to transfer the available power to the static wheel, the engine RPM will decrease as the load increases, which might be misconstrued as dethrottling.

Or, are you saying the system is so poorly calibrated that it will apply brakes to both wheels on the same axle?

Also, I have read that past certain throttle inputs and / or RPMs, the ATrac minimizes or ceases its interference. Can anyone speak to that?

As to the system preventing donuts and power slides, that is actually a function of the VSC, and not ATrac. That said, I am not concerned enough about the VSC preventing donuts and slides to disable it for the time being. If I really wanted to play in the ice and snow, I would just lock the center diff.

Its hitting the brakes so hard that it feels like your losing power and you do lose momentum even though you apply more pedal. So bad to the point he got stuck a few times.

Works great on the street in bad weather conditions. Just super deep snow, mud and climbing loose rock was an issue.

 

[Lindenwood]

Its hitting the brakes so hard that it feels like your losing power and you do lose momentum even though you apply more pedal. So bad to the point he got stuck a few times.

Thanks for clarifying your persoective. I am not a huge fan of mud, but I will look for that this weekend.

 

[RonJR]

Keep in mind that any ATRAC system that uses the brakes to control spinning will effectively double the torque required from the engine to maintain the same speed, vs an actual locker. This can certainly cause the engine to bog down unless you go into the obstacle geared low enough. This would be particularly true with the relatively limited torque of the 3rd gen 3.4 liter V6. It's less of an issue with the 4th and 5th gens with their higher torque engines.

True story: I once had to pull a Jeep Patriot up a rutted hill with my '94 because, with ATRAC off, the ruts were so deep he got cross-axled and simply spun helplessly, and with ATRAC on, the little Patriot engine combined with a fairly wimpy crawl ratio left him without enough torque to turn the wheels against the brakes. Simply stalled the torque converter. Obviously an inadequately designed system.

 

[JayRolla]

Keep in mind that any ATRAC system that uses the brakes to control spinning will effectively double the torque required from the engine to maintain the same speed, vs an actual locker. This can certainly cause the engine to bog down unless you go into the obstacle geared low enough. This would be particularly true with the relatively limited torque of the 3rd gen 3.4 liter V6. It's less of an issue with the 4th and 5th gens with their higher torque engines.

True story: I once had to pull a Jeep Patriot up a rutted hill with my '94 because, with ATRAC off, the ruts were so deep he got cross-axled and simply spun helplessly, and with ATRAC on, the little Patriot engine combined with a fairly wimpy crawl ratio left him without enough torque to turn the wheels against the brakes. Simply stalled the torque converter. Obviously an inadequately designed system.

This is also very true. But its still a major issue on my bros 4th gen with a v8 when in 4WD hi. When in Low its not as bad but still enough to cause issues.

 

[ltsr]

IMO, the primitive-by-todays-standards active traction system on 01-02 3rd gen is mostly useless. Might help a total 4WD novice get unstuck from some deep snow or mud and also help not to thrash the transmission, but not much else. Anyone experienced in 4WD, 4LO and lockers would probably never use ATRAC or disable. Want real traction? locker is only way to go.

VSC on the other hand can really save your bacon, even if you're a skilled and aware driver. Black ice and day-melt-evening-refreeze are no match for VSC and it's yaw sensor. If it works even once it was worth it. There was a video posted recently to the forum of a 3rd gen guy who lost it on melt-refreeze and rolled it. VSC works whenever the center is unlocked, RWD and 4HI. So if he'd been in an 01-02, he'd probably still be driving that rig today.

Retrofit a locker to '01-'02 plus ATRAC disable mod would restore the traction capability and retain the safety of VSC. Is on my bucket list.

Thanks for sharing that. But this is not a locker vs ATRAC question. The question still stands why is ATRAC bad?

Where are all the anti-ATRAC people with their detailed explanations?

I think the problem is that people compare ATRAC to 4runners with E-lockers.

 

[ltsr]

I have heard lots of "it sucks!" anecdotes, but despite reading pretty much every thread (on this forum and other offroad forums) connecting this model 4runner with "Atrac," I havent found any actual explanation for why it would actually be detrimental to offroad capability.

To clarify, I am not talking about the annoyance of having the VSC preventing powerslides in the snow and mud. Also, assume I am talking exclusively about wheeling with the center diff locked (i.e. VSC not active).

Also, just to clarify what I mean by "ATrac," and differentiate it from VSC, I'll quote the manual from the manual:




That is, ATrac only using the ABS system to apply brakes. The Vehicle Stability Control system uses both engine dethrottling and the ABS system to prevent slides.

Anyways, I am just looking for more illumination beyond "it sucks." Why, specifically, does it suck?

I'm really curious to find a real answer to why "it sucks" too. People so far in here have compared it to e-lockers, which is not a fair and proper answer. At least not to me.

 

[Lindenwood]

Keep in mind that any ATRAC system that uses the brakes to control spinning will effectively double the torque required from the engine to maintain the same speed, vs an actual locker. This can certainly cause the engine to bog down unless you go into the obstacle geared low enough. This would be particularly true with the relatively limited torque of the 3rd gen 3.4 liter V6. It's less of an issue with the 4th and 5th gens with their higher torque engines.

True story: I once had to pull a Jeep Patriot up a rutted hill with my '94 because, with ATRAC off, the ruts were so deep he got cross-axled and simply spun helplessly, and with ATRAC on, the little Patriot engine combined with a fairly wimpy crawl ratio left him without enough torque to turn the wheels against the brakes. Simply stalled the torque converter. Obviously an inadequately designed system.

This is certainly valid. However, in both your hypothetical and experiential examples, the vehicle would not have been able to traverse the obstacle without ATrac anyways (either due to lack of traction or lack of power). So, it still doesn't explain why offroad performance is actually worse with the addition of ATrac.

Thanks for sharing that. But this is not a locker vs ATRAC question. The question still stands why is ATRAC bad?

Where are all the anti-ATRAC people with their detailed explanations?

I think the problem is that people compare ATRAC to 4runners with E-lockers.

Thank you.

IMO, the primitive-by-todays-
standards active traction system on 01-02 3rd gen is mostly useless. bucket list.

I am still trying to figure out how we are going from it simply not being useful, to actively disabling it for some perceived benefit.

And indeed, I am not at all looking to compare any open-diff, brake-based traction control with lockers. I am trying to figure out why some feel having Atrac is actually worse than having just open diffs.

 

[Lindenwood]

If the mud or snow is deep enough you will literally be stopped and get stuck because traction control robbed you of all power.

. Might help a total 4WD novice get unstuck from some deep snow or mud and also help not to thrash the transmission, but not much else.

Also, not to single you guys out at all, but these statements are clearly contradictory. Again, not trying to be rude or disrespectful at all, but i do think this speaks to a relatively limited understanding of ATrac's function, across the community as a whole.


I have read that at higher throttle openings and / or higher RPMs (I have seen educated guesses of 2500-3500 RPMs), the ATrac system either limits its intervention or completely ceases it. The benefit here would be that if the tires are bogged in mud but are individually intermittently catching traction, the ATrac system would not limit mud-clearing wheelspin.

As far as the 4th gen getting stuck in the mud, if only one wheel on one or both axles was spinning (resulting in aTrac intervention), how would not having ATrac have prevented the vehicle from getting stuck? At that point, the only other option would be the low-traction wheel "diffing out," right? Do you think allowing the spinning wheel to keep spinning could have cleared enough mud to actually gain the necessary traction to continue?

Just trying ti deep-dive the problem because it doesn't seem like any of us really understand the system's actual functions, limitations, and capabilities.

 

[Darren]

My take is that if there are complaints, it would be directed towards the VSC system, not A-TRAC. I would guess people complaining don't know which system does what. That's speculation, though, as I've been off of the forums for the better part of 10 years. I have had a huge distaste for the dethrottling aspect of the VSC system. I almost got myself rear-ended pulling out onto a dry main street from an icy side street the first night of owning my '02. I pulled out with plenty of room, but I sat going about 3 MPH for a few seconds just being stalled in the street. That's also happened a couple other times through the years because it slips on a few pieces of gravel when pulling onto a main street. I was expecting to see a lawsuit on it, but I don't think that happened. It is that bad. I do like the braking aspect on it if you begin to slip, though I really haven't had that come into play at higher speeds. I believe I had seen right after the 4th generations came out that they had tuned both systems better. I would certainly hope so.

On the other hand, A-TRAC is better than an open diff machine without, and certainly that's the case on rocks and moguls. I've been in mud a few times (in low range), but it has been a good number of years (I've been double-locked since ~'04), but never once did that system limit anything. To be honest, I don't even recall that it ever even engaged in mud. I've been in deep snow far more times, which is essentially the same thing, and it has never been any kind of detriment. It will spin all four all day long. If someone happens to leave the rig in AWD mode with the center diff open, then yeah, VSC is going to stop you, but I can't think A-TRAC would. It sounds like you have a good understanding of the system, so I'm not adding much other than reinforcing your ideas.

Retrofit a locker to '01-'02 plus ATRAC disable mod would restore the traction capability and retain the safety of VSC.

That wouldn't restore traction ability, that would add to it. There would be no need to disable the A-TRAC system if you have a locker, as the system wouldn't even engage on the rear axle at that point. You would then still retain the limited slip properties up front, should you not lock that end.

 

[JayRolla]

I'm not sure how the system works. Not sure what system stops you in your tracks.

All i know is I've always read about the issues and why to disable. I felt the issue first hand in brothers rig when he tried to do a donut in dirt and the truck would not do it.

I told him how to disable sand he has been happy since.

 

[AntleredRuin]

Its hitting the brakes so hard that it feels like your losing power and you do lose momentum even though you apply more pedal. So bad to the point he got stuck a few times.

Works great on the street in bad weather conditions. Just super deep snow, mud and climbing loose rock was an issue.

Does this apply to the front wheels or just the rear? I'm a 99 2wd so this all unknown to me. If it applies to the front wheels as well, that would definitely not help with the subpar stock brakes the 3rd gen comes with. It brakes harder the 'faster' you go? 'Warped' rotors instantly.

 

[SnowLizard]

OK, this thread is 100% full of 'they say' 'he say' 'manual say'... Which isn't a bad thing, I want to see some action of aTrac here's what I propose. I feel this discussion will continue without some tests in the real field

lets use a 99-00 with locker+vsc
lets use a 01-02 with vsc+aTrac

lets take both vehicles on the same path in different modes:
99/00----------01/02
2wd----------2wd
AWD---------4hi unlocked
4wd----------4hi locked
---------------4low unlocked
4low-----------4low locked
4low rLock------------

the above is all the modes either can use 'from factory'... no vsc disable or anything... just factory settings.

Lets record the performance and post them up on youtube. I think EVERYONE can benefit from the experience.

the terrains needed are the following...
Loose rock/gravel hill climb
Deep Mud
Deep Snow
'rock crawling step'

I only add the locker cause if we are going to do it, we might as well do it all once.

this only requires 2 4runners, and a video guy with video editing skills.

 

[papapoopski]

I have seen the benefit of ATrac in axle deep mud first hand in my 02. I could hear and feel the system actively working to gain traction.

To further muddy the info getting thrown around. Would the Tundra brake upgrade affect the ATrac system since it is using braking?

 

[Lindenwood]

My take is that if there are complaints, it would be directed towards the VSC system, not A-TRAC. I would guess people complaining don't know which system does what.

This is what I am starting to gather.

OK, this thread is 100% full of 'they say' 'he say' 'manual say'... Which isn't a bad thing, I want to see some action of aTrac here's what I propose. I feel this discussion will continue without some tests in the real field

lets use a 99-00 with locker+vsc
lets use a 01-02 with vsc+aTrac

lets take both vehicles on the same path in different modes:
99/00----------01/02
2wd----------2wd
AWD---------4hi unlocked
4wd----------4hi locked
---------------4low unlocked
4low-----------4low locked
4low rLock------------

the above is all the modes either can use 'from factory'... no vsc disable or anything... just factory settings.

Lets record the performance and post them up on youtube. I think EVERYONE can benefit from the experience.

the terrains needed are the following...
Loose rock/gravel hill climb
Deep Mud
Deep Snow
'rock crawling step'

I only add the locker cause if we are going to do it, we might as well do it all once.

this only requires 2 4runners, and a video guy with video editing skills.

While I will always support good data gathering and experimentation, the intent of this thread wasn't to compare ATrac to a locker, and I don't think anyone expects the former to really match the latter.

That said, I intend to do a bit of playing this weekend to see what I can find.out.

ATRAC: Negligible traction gain and doesn't allow donuts while carrying risk of de-throttling when you try to pull into traffic with what seemed to be plenty of room. Install a disable switch so you can decide when you want it on/off.

VSC: Can save your truck from skid outs and wrecks. A good thing if you have it.

Again, dethrottling and donut / skid-prevention are solely functions of the VSC system, not ATrac.

Bottom line: I am really just trying to figure out under what circumstances an open-diff 4runner could actually perform better in 4Low offroading without ATrac.

 

[Lindenwood]

The above statement is not correct. ATRAC (Active TRAction Control) will cut or reduce throttle as it sees fit to help accelerate (which requires traction). Park all 4 tires in mud and press the gas pedal to the floor. Watch ATRAC take over throttle control while wheels are spinning. Now head to the power wash.



This question is a bit absurd. If you've got reason to be in 4LO you've probably got reason to have the center locked at which point ATRAC is disabled, so the question becomes moot.

4LO means typical speeds in the 1-20 mph range which is a HUGE range. If you're in 4LO you're probably expecting lots of sand, mud, snow, loose ground, rocks, steep climbing, ruts, broken/uneven terrain, or any or all combination of the above. Under just one of those conditions ATRAC may help keep the vehicle moving, under several of them it will not. There is no one size fits all right answer. ATRAC is a hell of a lot better on 5th gens and FJs than it is on 3rd gen. Again, why are you in 4LO with the center unlocked anyway? About all that's good for is a curved boat ramp or backing a trailer up a steep driveway.

Before calling anything "absurd," you should realize that
All evidence, including the manual itself, explicitely contradicts the two major aspects of your post:

1) It is the VSC, not ATrac, which has the ability to control throttle.

2) Only VSC, not ATrac, is disabled with the center diff locked.

Thus, only ATrac would be a factor in a 4Lo, diff-locked situation, and none of the functions and outcomes you mention (dethrottling) actually apply to ATrac.

As to the bolded part of your post, can you articulate why? I know it is very well-regarded in the FJ and 5th Gen communuty (and I have seen it work with good results). I am just curious what specifically makes it worse in the 3rd gens (longer response times? Less smooth brake inputs? Higher wheel-speed differentiald required? We do have one reasonable hypothesis that the weaker 3rd gen engine can't keep up with the doubled effort required.).

But, really, it sounds like I'll need to do my own testing, because apparently nobody really has the answer, heh.