A-trac
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chaz
New member
a few threads on it, this isnt a bad place to start. http://www.toyota-4runner.org/4th-gen-t4rs/5036-how-does-atrac-work.html
A-Trac is automatically engaged once the Center Differential Lock switch is engaged. It would be nice to have a switch for A-Trac for the 4th gens, yes 5th gen has the A Trac button.
Hmmmm. I didn't know atrac won't kick in if diff is not locked. I read it won't engage if the speed is above a certain speed.
So if I'm driving slow and hit a mud on one side and there is slippage atrac won't kick in if diff are not locked, is this correct?
chaz
New member
op, didnt you bring this up a few years ago? either way, seems the forum will always be divided, half say it works in 4HI CD unlocked others say only 4L CD locked, just to make it more confusing, http://www.toyota-4runner.org/4th-gen-t4rs/117378-atrac-4lo-only-not-4hi.html
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alpinhi
New member
I have read few threads on this subject. I recently purchased a 05 V8 4Runner last spring. Im coming out a Unlimited Jeep Rubicon and I wanted to know how this ATRAC thing worked so I messed around with it quite abit. This is what I discovered for the V8 model, may be different in the V6. The ATRAC is always active no matter whether the CDL is locked or not. I think some people may be confusing ATRAC with TCS or traction control system. My 4Runner is equipped with both systems. While in Colorado this year I attempted a climb up a rutted out hill which I didn't think much about it until I hit a point on the hill where the T4R lost all forward momentum. The right front tire was in the air and the left rear was barley touching the ground. I noticed the T4R made all sorts of weird clicking noises as it tried to transfer power to the tires with traction, it also cut back my throttle and would not let go much over idle. The Traction control system cut back the power to attempt to keep me from spinning my tires, mean while the ATRAC attempted to put power to the tires that were making contact with ground. Neither of these were successful in restoring forward momentum. At this point i backed up a bit and regained traction and I locked the center diff with T-case still in high and attempted it again. This time there was no loss in power because when I locked the center diff the TCS is disabled. The crazy clicking noise was there as the ATRAC once again attempted to put the power to the tires with traction, no luck. I backed off and attempted it again with CD locked and in 4Lo and I got the same results as the previous attempts.
So what I have come up with is ATRAC and the TCS are always active (V8 models) with the CD unlocked. Once you lock the CD the TCS is disabled but ATRAC remains to allow you to get some wheel spin and hopefully push you through the situation. The same can be said for 4Lo also. In my opinion the TCS doesn't really help (on any vehicle) and the ATRAC is ok for mild off road use and muddy/snowy roads. When you are in situations where tires are off the ground and traction is completely lost the ATRAC system isn't enough to get it done. Time for a real locker(s). If there is a Yota guru out there who reads this please correct me if Im wrong. Hope this helps some.
Travis
So what I have come up with is ATRAC and the TCS are always active (V8 models) with the CD unlocked. Once you lock the CD the TCS is disabled but ATRAC remains to allow you to get some wheel spin and hopefully push you through the situation. The same can be said for 4Lo also. In my opinion the TCS doesn't really help (on any vehicle) and the ATRAC is ok for mild off road use and muddy/snowy roads. When you are in situations where tires are off the ground and traction is completely lost the ATRAC system isn't enough to get it done. Time for a real locker(s). If there is a Yota guru out there who reads this please correct me if Im wrong. Hope this helps some.
Travis
alpinhi
New member
I believe you are correct. ATRAC uses the ABS to transfer power. If your ABS light is on then it is probably not operating along with ATRAC. Im not sure why all those would be on, you might try stomping the brakes on a gravel road to see if the ABS kicks in or not.
ATRAC works by pulsing the brakes (loudly) to control slipping wheels. If it's not doing that, you are just feeling resistance from the locked center.
Ocean Racer
New member
2007 V8 4Runner
I am still confused about how well this works.
What I was expecting from the A-Trac was that it would work as a crawl control as the FJ's were boasting about in 2013-14. I had it locked in Low, with ATrac engaged and locked in 1st gear and it did not keep my slow enough to go down a steep incline. I still had to stay on the brakes.
SO I still don't see the point in this feature. Let me know!
I am still confused about how well this works.
What I was expecting from the A-Trac was that it would work as a crawl control as the FJ's were boasting about in 2013-14. I had it locked in Low, with ATrac engaged and locked in 1st gear and it did not keep my slow enough to go down a steep incline. I still had to stay on the brakes.
SO I still don't see the point in this feature. Let me know!
Are you thinking of DAC? That automatically pulses the brakes to control your speed down hills. Unlike CRAWL, it does not give it any gas. It is a bit too fast IMO, but it helps in some situations. There is a DAC button that looks like a 4runner on a wedge.
ATRAC basically simulates limited slip front and rear differentials to keep wheels from slipping if they lose traction. You still have to use the gas, and it will automatically activate if a wheel breaks traction. It mainly only works if you are using the engine to accelerate.
Synister
Member
Lots of confusion here and some misinformation too.
There are 3 systems on the truck: TRAC, VSC, and ATRAC. You could include ABS here as well but for our purposes, we'll omit.
TRAC is "traction control", if a wheel spins, it will apply the brakes to that wheel AND ALSO cut engine power until traction is restored. People who live in the snow hate this feature. This is always on and it wasn't until 2007 (I think) that you could turn it off by holding the VSC button down for 3 sec.
VSC is "vehicle stability control" and it works with the ABS, steering wheel position sensors, and yaw sensors to determine if the vehicle is tracking in a straight line. It is tied in to the TRAC function as well, hence the auto braking, but can be disabled by the VSC button. Pushing this button does not turn off TRAC.
ATRAC is "active traction control" and is for off road use only. It only works in 4LO, despite what you may think. In 4HI, what you are experiencing is TRAC, and its likely also limiting engine output somewhat. It senses a loss of traction on one wheel and applies the brakes (without cutting engine power) to that wheel in order to send torque to the opposite wheel with traction. It does this by pulsing the master cylinder several times a second so you can hear and feel it in the brakes. There is no light or anything to let you know its working, its in the background and like I said only works in 4LO, below 5mph, because that is where you get the most torque advantage at low speed.
The FJ cruiser, Tacoma TRD Offroad, and the 4th gen Trail Edition, have selectable ATRAC, meaning there is a switch for it and a light on the dash. This switch also only works in 4LO and the system on these two vehicles is more aggressive that the standard background ATRAC on the rest of the 4runner line. Its is extremely effective if you use it properly. Is it better that a locker? In some situations, no, but its safer and easier to use on the front diff than a locker in many situations where a front locker might get you in trouble.
Before you jump on me for that last comment, think about how many posts over the years asking about how the 4wd in our trucks works, what is ATRAC, what is VSC, and think about how the Toyota lawyers would feel about a front locker vs. a braking system that closely mimics it with less liability.
ATRAC is not designed to help you down a hill, nor is the fact that you see skid marks while turing on pavement with the center diff locked indicative of the system working. If nothing else, just remember it only works in 4LO and takes some revs to make work best, ~2000-2500.
Cheers
There are 3 systems on the truck: TRAC, VSC, and ATRAC. You could include ABS here as well but for our purposes, we'll omit.
TRAC is "traction control", if a wheel spins, it will apply the brakes to that wheel AND ALSO cut engine power until traction is restored. People who live in the snow hate this feature. This is always on and it wasn't until 2007 (I think) that you could turn it off by holding the VSC button down for 3 sec.
VSC is "vehicle stability control" and it works with the ABS, steering wheel position sensors, and yaw sensors to determine if the vehicle is tracking in a straight line. It is tied in to the TRAC function as well, hence the auto braking, but can be disabled by the VSC button. Pushing this button does not turn off TRAC.
ATRAC is "active traction control" and is for off road use only. It only works in 4LO, despite what you may think. In 4HI, what you are experiencing is TRAC, and its likely also limiting engine output somewhat. It senses a loss of traction on one wheel and applies the brakes (without cutting engine power) to that wheel in order to send torque to the opposite wheel with traction. It does this by pulsing the master cylinder several times a second so you can hear and feel it in the brakes. There is no light or anything to let you know its working, its in the background and like I said only works in 4LO, below 5mph, because that is where you get the most torque advantage at low speed.
The FJ cruiser, Tacoma TRD Offroad, and the 4th gen Trail Edition, have selectable ATRAC, meaning there is a switch for it and a light on the dash. This switch also only works in 4LO and the system on these two vehicles is more aggressive that the standard background ATRAC on the rest of the 4runner line. Its is extremely effective if you use it properly. Is it better that a locker? In some situations, no, but its safer and easier to use on the front diff than a locker in many situations where a front locker might get you in trouble.
Before you jump on me for that last comment, think about how many posts over the years asking about how the 4wd in our trucks works, what is ATRAC, what is VSC, and think about how the Toyota lawyers would feel about a front locker vs. a braking system that closely mimics it with less liability.
ATRAC is not designed to help you down a hill, nor is the fact that you see skid marks while turing on pavement with the center diff locked indicative of the system working. If nothing else, just remember it only works in 4LO and takes some revs to make work best, ~2000-2500.
Cheers
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techno
New member
This is incorrect for 2008 models.
TRAC (traction control) is only on 2wd models. ATRAC (Active Traction Control) is on 4wd models.
There is another function called AUTO LSD, but it's only on 2wd and multi-mode 4wd models.
Sort of right for 2008 models.
On 4wd models, ATRAC is always on when you start the car and remains on until you turn off intentionally. Pressing the VSC OFF switch once turns the AUTO LSD on and ATRAC off. I'm not totally sure of the difference between normal atrac and auto lsd, but it seems that one does not regulate the engine power and the other does. In my experience, the auto lsd provides more 'get out of the mud' ability than normal atrac.
If you press and hold the VSC OFF switch for 3 seconds, then it turns VSC off too.
Incorrect for 2008 models again.
TRAC is on on 2wd models, ATRAC is on 4wd models and is always on, regardless of what transfercase setting you are using. When the system detects a traction issue and starts doing it's stuff, the slip indicator light flashes and you can hear lots of clicking noises from the engine bay.
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If the center dif is locked then ATRAC works in 4Hi just the same as it does in 4Lo. I use it on a weekly basis, or more. There is no difference in how it works between the two modes of 4wd, your just moving slower in 4Lo. Some of the later models and especially the Trail Edition had other options that further complicate this, but it is the same in essence.
and you are correct, it works quite well! I had tires in the air last night and it kept me moving without problem. Little noisy, and feels weird bumping and lurching like it does, but next best thing to a locker!
Isn't there a table for the different program available in each mode? I can't find it now. Here's one for FJs:
And here's one for Tacomas:
4runners are probably slightly different, and there might be slight variations between 4th gen model years.
There's more detailed discussion in this thread:
http://www.toyota-4runner.org/4th-gen-t4rs/5036-how-does-atrac-work.html
For most people, I would give this advice:
Don't worry about all these acronyms. That's mostly just marketing buzzwords for similar functions. Just go drive and you will probably get traction when you need it. If not, try changing between 4Hi and 4Low or locking or unlocking the center. It's best to experiment and see what works for you.
And here's one for Tacomas:
4runners are probably slightly different, and there might be slight variations between 4th gen model years.
There's more detailed discussion in this thread:
http://www.toyota-4runner.org/4th-gen-t4rs/5036-how-does-atrac-work.html
For most people, I would give this advice:
Don't worry about all these acronyms. That's mostly just marketing buzzwords for similar functions. Just go drive and you will probably get traction when you need it. If not, try changing between 4Hi and 4Low or locking or unlocking the center. It's best to experiment and see what works for you.