Off-road situations where the A-Trac really shines?

[Jeremy556]

Any comments or input from other Trail owners on ATRAC vs Multi-Terrain??

I only use MTS in the 1st setting in 4hi - it makes the TRAC and ABS systems less intrusive on unpaved surfaces. In 4lo I use ATRAC by default with lockers as needed.

I have ATRAC brake a spinning wheel as it leaves the ground at idle engine speeds all the time. I think it has to do with the speed of wheel spin and less/nothing to do with engine RPMs.

 

[3wbdriver]

I got stuck on purpose in snow trying to understand its usefulness.

I read most of the posts before deciding to chime in. Deliberately getting stuck or close to it is not the best way to test A-TRAC. Engaging it when you expect to possibly get stuck is the best use. Then you go to the locker if A-TRAC is not enough. My 2011 Tundra was a 2wd with an open rear diff, but it had electronic limited slip (rear wheel A-TRAC if you will). That limited slip pulled me across 2 rig locations that were soupy mud when other guys were having to engage 4wd to get across. On both occasions the rear brake anti-slip engaged before I got much above idle and as soon as it detected more than a little wheel slip and allowed me to maintain forward progress across 100 yards of mud until I could get to higher ground. The light was blinking in the dash the entire time, but I only held enough throttle to keep it rolling without overpowering the system.

A-TRAC is not designed to LOCK up a spinning wheel. It is designed to dab the brake slightly on that wheel, slowing it down, and transferring some of the energy to the wheel with traction. It will not LAUNCH you into a tree or over the edge of a cliff. It will simply assist you in maintaining forward motion.

CRAWL control is simply a combination of A-TRAC and choking the engine down to prevent excess wheel speed.

I will admit I haven't messed with the Multi-terrain mode very much, so I have no input there. With that capabilities of A-TRAC and the e-locker I just haven't seen a need to use it.

 

[Intruder]

I don't think I understand this thread. To me it sounds like the situation in the original post wasn't a good situation for ATRAC - he probably dug in to the frame and high centred by getting on the throttle too much. Deep snow requires slow and steady acceleration, low tire pressure, and decent amounts of momentum. ATRAC and momentum don't really go together.

 

[Jhalko]

Deep snow requires slow and steady acceleration, low tire pressure, and decent amounts of momentum. ATRAC and momentum don't really go together.

The above advice is all I need, because there is no one on this site whose snow driving advice carries more weight in my mind. If you doubt it, go through his thread.

 

[MoonStorm]

Please don't get sidetracked into what's the best way of wheeling, tires, pressure and what not.

No, the frame wasn't touching. And the person outside was watching both wheels from the front and then from the back. Only when reaching about 1500 RPM the dash informed me about tire slippage and that was also the moment the other tires started spinning as well, together with the regular grinding noise. Other people reported same findings on this forum and I got to experience that first hand. Don't take it as exact science though, it's in the ballpark of 1500 and it might as well have nothing to do with that. However below that RPM value the system seems to have stayed dormant.
And as an FYI, the car was not going side to side either. It was still stationary as it happily started digging holes in the snow and then in the soft ground with the two tires spinning, as I reported in my original post.

Thanks for all your posts, but I do feel though there's a lot of speculation involved unfortunately. We report what we experience, but I would love to know more, or to see some more in-depth documentation on the subject, rather than the simple "oh it just tricks the open differential by braking the tires with less resistance". We all know that already.

However, you guys did touch on a point. The system might behave differently in motion versus being stationary, or the information from the sensors might get disseminated differently. Because I could swear the truck feels more sure footed even in let's say "normal conditions" in this mode versus the counterpart 4L terrain select, as I wrote in my first post, when wheeling on dry trails with loose rocks and steep inclines. And with none of the ABS sounds or light lit on the dash which means no detected slippage and hence no wheel braking, right? The animal feels like it's sticking claws into the ground when it climbs. So what else goes on behind the scenes in this particular mode? Or maybe I'm imagining things...

 

[CrazyNorwegian]

A-trac works fantastically when you have wheels in the air on slow technical stuff. It become very annoying/useless in mud and deep snow where momentum/wheel speed can help you. I usually leave it off unless I see a obstacle that may require it.

 

[Jhalko]

Please don't get sidetracked into what's the best way of wheeling, tires, pressure and what not.

Thanks for all your posts, but I do feel though there's a lot of speculation involved unfortunately. We report what we experience, but I would love to know more, or to see some more in-depth documentation on the subject

Speculation? It's real world usage and experience talking, these guys know what they are talking about since they are the ones the engineers make this stuff for, not some mall crawling yuppie (like me). Trust the info they are giving you and don't over analyze what the computer is trying to do.

If that isn't what you want you should be reaching out to the Toyota engineers themselves.

 

[MoonStorm]

Speculation? It's real world usage and experience talking, these guys know what they are talking about since they are the ones the engineers make this stuff for, not some mall crawling yuppie (like me). Trust the info they are giving you and don't over analyze what the computer is trying to do.

If that isn't what you want you should be reaching out to the Toyota engineers themselves.

I meant speculation on the inner workings of the system. You're right, I'm perhaps looking for an answer from people with more in-depth knowledge.

 

[pauldavis]

The title of the thread is "off-road situations where atrac really shines" . All the replies did a great job covering that and comparing it to and with the other off road features the 4runner has. Plus talking about where it doesn't shine. Exactly what the op asked for yet he is not satisfied. By the way you can't talk about one feature like atrac without bring up others like a locker, crawl control, or tire pressure because these help to show similarities, differences and how they can work together with atrac.

 

[tigger]

I have to wonder what your actual wheel speed would be at 1500 RPM in first gear. Maybe 2-3 mph. It takes about a half a second to hit 1500 rpm in 4L. Not really long enough to sit and spin two tiers while sinking. Unless you were just trying to idle out while sitting there, I am not sure how real world of a test that was for snow use. The jolt is minimal. It is applying pressure to the brakes on the traction side, but it's not the equivalent of slamming on the brakes.

I haven't tried it in snow, but know if pretty effective on rocky trails when you are off camber or in loose granite. It got me through some spots in Big Bear that others were surprised that I didn't have a locker.

 

[MoonStorm]

The title of the thread is "off-road situations where atrac really shines" . All the replies did a great job covering that and comparing it to and with the other off road features the 4runner has. Plus talking about where it doesn't shine. Exactly what the op asked for yet he is not satisfied. By the way you can't talk about one feature like atrac without bring up others like a locker, crawl control, or tire pressure because these help to show similarities, differences and how they can work together with atrac.

Right. So basically people on this forum don't read the post, just its title. Good to know...

 

[pauldavis]

Right. So basically people on this forum don't read the post, just its title. Good to know...

No, they actually answered all the questions in your first post as well but your too busy replying to people in a condescending way to listen to any of them.

 

[MoonStorm]

I have to wonder what your actual wheel speed would be at 1500 RPM in first gear. Maybe 2-3 mph. It takes about a half a second to hit 1500 rpm in 4L. Not really long enough to sit and spin two tiers while sinking. Unless you were just trying to idle out while sitting there, I am not sure how real world of a test that was for snow use. The jolt is minimal. It is applying pressure to the brakes on the traction side, but it's not the equivalent of slamming on the brakes.

I haven't tried it in snow, but know if pretty effective on rocky trails when you are off camber or in loose granite. It got me through some spots in Big Bear that others were surprised that I didn't have a locker.

When you say rocky trails, do you refer to big boulders? Because I was wondering how it feels on those, having one or two tires having lost traction. I am afraid it would be too unexpected in those circumstances when it kicks in.

RPM wise, I get what you're saying, but it's still too high, especially in some conditions. Don't understand why it doesn't kick in sooner. But again, as I said a few posts up, it might behave differently in motion. Btw, could you remember what speed or RPMs you had when you felt it working?

 

[MoonStorm]

No, they actually answered all the questions in your first post as well but your too busy replying to people in a condescending way to listen to any of them.

Could we keep this civilized please? Thanks.

 

[MoonStorm]

The wheel speed sensors pulse.. The granularity is not analog... The system tries to detect deltas, but from a dead stop its not that fast. Also, the system is pulsing the brakes to equalize tq output from the open diff.. it can't be super aggressive and stay reliable... once the TQ output goes high... It needs to back down. the ABS system is primarily for braking and they don't want it to blow up doing double duty as a traction aid to get you out of mud (when a locker is simply a better solution).

This is not unique to Toyota. ATRAC is pretty much best in class... There is always room for improvement.. but why bother when lockers can easily fill the void. With unlimited budget.. I'm sure a better system could be designed, but most people here find it quite adequate for its intended use.

Good explanation thanks. However it doesn't seem to relate to my experience. The system remained dormant as I was applying constant acceleration below that RPM threshold, even when lingering more in that range. And I certainly didn't see it backing down above that, as long as it sensed the tires spinning in vain.

 

[tigger]

When you say rocky trails, do you refer to big boulders? Because I was wondering how it feels on those, having one or two tires having lost traction. I am afraid it would be too unexpected in those circumstances when it kicks in.

RPM wise, I get what you're saying, but it's still too high, especially in some conditions. Don't understand why it doesn't kick in sooner. But again, as I said a few posts up, it might behave differently in motion. Btw, could you remember what speed or RPMs you had when you felt it working?

Wasn't paying attention to the RPMs, was too busy trying not to hit the rocks :tongue1:

Sometimes they were large rocks, other times large washouts in the trail where you only had two tires touching the ground. As for the feeling, you hear it more than you feel it. You will be in a spot with the tires spinning then hear the system kick in. It is very loud and disconcerting the first time you experience it.

My last 4x4 was a built Rubicon with front and rear lockers. My 4runner was definitely a step down in capabilities, but I was surprised at what it did get me through (at the cost of skids and a rear bumper cover :suspicious: )

 

[mo_mo]

I've not used A-trac often and I haven't put my 4Runner in snow. A-trac worked well for me at low speeds with high slippage (loose and slow climb). I suspect that in snow A-trac wouldn't work very well as all wheels will readily spin at the same speed and so the vehicle won't recognize that there is slippage. In my previous vehicles I've always used 4-hi for snow and A-trac requires 4-lo, so it isn't the intended purpose although it might help if you can manage to find traction on the white stuff.

 

[1engineer]

Could we keep this civilized please? Thanks.

This is by far one of the more civilized threads. When 15 people answer a certain question the same way then the problem is usually not with the 15 people, it's with the one asking the question.

1500 engine RPM has nothing to do with it. You were in one very specific situation and you were immobile. Listen:

The wheel sensors are set up to detect a delta between the wheels, just like VSA. When you have all wheels in the snow who knows WHAT wheel will be the one with traction. So in essence a wheel needs to spin at a differential RPM from the other wheels before the processor will analyze the signal and determine the best course of action for that specific wheel. Now, it has to also determine that this differential RPM is NOT caused by common everyday occurrences like: Sharp turns, worn tires, low air pressure in one tire, etc. You see, all these things will cause a differential RPM between wheels too so the differential between wheels has to be GREATER than it would be in everyday driving. In addition to this, you need to note that ATRAC works at other speeds besides "stuck" which is the ONLY condition you tested. So, while in your specific case the speed the ATRAC actuated "felt" excessive, if you were traveling 15 mph then the ATRAC would be performing it's task of braking spinning wheels without any discernible trigger.

In order to accelerate in the snow or on extremely slick surfaces you need to be on the edge of traction. You know that area between going forward and spinning? Yeah, there. In order to be at that point ATRAC will be DETRIMENTAL to your forward progress instead of helping go forward. That's why Toyota thoughtfully included a "VSC OFF" button. This way if you are stationary on a slick hill and you need to move forward you can turn VSC off and allow your tires to break traction and spin in order to get on that "edge" of traction. ATRAC or VSC in that situation will brake your wheels or retard your throttle and keep you stuck!

Now, if you would have read these very good responses from a lot of good people who took time from their weekend to try to help you understand, then you would have come to the same conclusion as I outlined above. Instead you came here looking for a specific answer to fit your one test. In snow, ATRAC or VSC is not going to help, unless you already are at speed.

 

[Ammomac]

Could we keep this civilized please? Thanks.

i'm just glad you didn't say you are in a TRDP...

they get really ugly with that

:eyebrows:

 

[BobsTrail]

A-trac works fantastically when you have wheels in the air on slow technical stuff. It become very annoying/useless in mud and deep snow where momentum/wheel speed can help you. I usually leave it off unless I see a obstacle that may require it.

I'm still hung up on using M/T instead of ATRAC. I used it in 4H and was able to keep the wheels spinning on the edge of traction as [MENTION=66316]1engineer[/MENTION] states without the throttle reduction. I expect I need to try the same in 4L and then ATRAC to see if there is a difference. Wish I would have seen this thread a few days ago when we were in the local mountains.