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Old 05-31-2005, 02:05 AM   #1
Cruiserhead
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Default Understanding & Using ATRAC II+

This thread will contain info on how to use ATRAC effectively in your rig. Misunderstanding it's capability can lead to frustruation while driving offroad. Pleas add your experience and tech info!

All 120 platform suv's use Toyota's ATRAC II+
It is improved over the Land Cruiser 100 ATRAC II and a big leap forward from 3rd Gen 4Runner ATRAC I. It uses 2 sensors per wheel (not 1) to more accurately and quickly react to situations.

Here is an excerpt from Overlander.com's Prado 120 review:
"The most impressive of these systems is the second generation A-TRC traction control. Second gen’ A-TRC was introduced on the latest 100 Series but Prado Chief Engineer Kunihiro Hoshi says that the system in the Prado 120 is better still. It does work extremely well. On a steep, rutted climb on the test loop, the Prado Grande crawled up with ease despite the fact that we deliberately took a hard line and lifted wheels in the air. More senior members of the 4WD press were heard to mutter “A 40 Series wouldn’t have got up there”, as their old-school mates nodded in agreement."
http://www.overlander.com.au/pg/vehi...sts.php?id=216

Another KEY FACTOR is the use of Center Diff Lock (button located to the left of the steering wheel on the lower dash. The button has a diagram of the 4 wheels and X in the center).
Without the center differential locked, your VSC (vehicle skid control)remains on. In this case, it will cut power to your wheels just when you may need it the most.
LOCKING the center diff, thus turning off VSC (a light on your dash will indicate "VSC OFF") will allow you to go as any other 4x4 vehicle without electronic traction devices engaging.
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Old 05-31-2005, 02:05 AM   #2
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From Bulldog:

I have done quite a few offroad trips with my 4Runner, which has exactly the same ATRAC systems as the GX. The trick is to lock the center diff and apply just enough gas for the system to kick in properly. Rule of thumb is to keep at 2000 or so RPM. What tends to happen is that people back of or give more throttle when encountering an obstacle which makes it difficult for the ATRAC system to respond correctly. Just keep the throttle constant at 2k RPM with center diff locked, you will get used to the brake system clattering. It works really well.

Video going up a pretty steep hill with loose gravel, and one rear and one front wheel off the ground.

EDIT:
I have another one of going through a mud pit and again the same situation. WIll try to post it later. But here is a picture. Ok here is the video. Notice that when I let of the throttle the one rear wheel stops, then when I apply throttle again it start going.

As addition [by Bulldog]. On rocks you will probably want to use lower engine and vehicle speed. When you get to the obstacle you will then want to accelarate gently, this seems to make the TRAC work pretty well when it senses slight accelaration. DOnt pound on the gas peddle just add a bit gently.
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Old 06-02-2005, 07:20 PM   #3
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Here are a couple of videos showing ATRAC and what it can do and what it sometimes does when you dont use it right.

ATRAC done right:
Hill climb with low traction and 2 wheel off the ground. Video
Mudpit, again with low traction taking one rear and one front in very low traction mud. Video

ATRAC and applying too much gas actually doesn't get the job done right. Video


ATRAC used in combination with rear locker. Video
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Old 06-18-2005, 02:47 PM   #4
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The key is to keep steady gas- dont accelerate or "gun it" when you feel it slipping. As it slips, you will hear and feel it "rat-tat-tat" That is the Traction Control kicking in and your truck will begin to climb.

When it starts to move, keep steady gas- dont accelerate even tho it's moving- let the truck do the work. If you are still slipping, try turning the wheel right to left to hunt for traction. This will get your tires to hook up most of the time.
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Old 07-02-2005, 12:43 AM   #5
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Another cool vid from downunder with ATRAC in action.
Video
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Old 11-27-2005, 10:06 PM   #6
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It works the same way in the 1st gen A-trac very well, but sometimes it seems its not holding long enough. When i test drove my cousins 05 SR5 in carnegie, i wasn't impressed in the mud, probably cuz i was gunning it lol. Does the new A-Trac shut off traction control after constant use and usually gives a warning beep? I tried my a-trac to the max on this one part of hollister, i cant remember the name but it was a steep hill climb with lots of shelves and offcamber climbs. It beeped and i had to wait 45 seconds till it cooled down.
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Old 11-27-2005, 11:35 PM   #7
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I have yet to heat up the brake system to the point that ATRAC of DAC doesn't work anymore.

ATRAC will not help you much in mud if the tires are not up to task, same as lockers. But as stated, when you gun the throttle ATRAC disables itself.

Hope you can make Hollister, I would like to see how the earlier ATRAC compares.
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Old 11-28-2005, 07:34 PM   #8
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I guess your right, considering I have big treads vs stock tires that came with the 4th gens. Basically, the ATRAC on the 4Runner works like teh ATRAC on the LandCruiser...thats how it seemed to me, you just have to keep the throttle at lower rpms. But since the new gen ATRAC has 2 sensors, i bet its alot more accurate than the 1st gen. My axle was supposed to arrive today....no axle yet. I'm going to calll Napa tomorrow and Global Auto parts, just in case they havem instock, and if they do i'll buy it and the one that comes from Kragen will be a spare...untill tomorrow, we'll have to wait for shipment results. Never thought a simple axle is this hard to get...
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Old 02-08-2006, 03:05 AM   #9
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Default ATRAC System

Does anyone no about the Atrac System on a 02 4runner (4x4)? I was wondering what the difference between a Atrac II vs Atrac.
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Old 02-08-2006, 08:43 AM   #10
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I am not too familiar with the 3rd Gen Atrac system. I'm not sure if it allows you to turn off the VSC (which is what cuts power to the engine under certain conditions and therefore not what you want). I have heard numerous reports that the Atrac on the 3rd Gens have not been tuned agressively enough to effectively help in harder offroad situations. People have reported back that the Atrac on 4th Gens have worked far better in hard offroad conditions than the 3rd Gens could. It seems that the AtracII was tuned more agressively than the original Atrac. I don't know if it is possible to tune or upgrade the Atrac system on the 3rd Gen to be more agrresive. Best is just to make sure the VSC is off, so no throttle reduction is done.
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Old 02-08-2006, 10:05 AM   #11
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Atrac in my 02 4Runner works very flawlessly. It wont work as effective your mashing the gas, and sometimes it wont work at all. You have to keep your rpms low and wheelspeed to a minimum. The reason I found the Atrac doesnt work at higher rpms is because the computer is thinking your cruisin in the dunes, or stuck in a mud puddle, where Atrac is welcome. I have been in LOTS of tough offroad situations from 2002 to the end of 2005, and I rely on my Atrac too much.

3rd gens with ATRAC systems have a lockout for the VSC wich locks the center differential. Without locking it out, you have all wheel drive mode and stability control. I am not to comfortable about the rear drum brakes, but in sticky situations, they havent failed me.

There was this one time I was 4wheelin and i didnt see the slippery muddy part, and i came a tad bit to fast and my truck slid and the right side tires were in the air while the under body and left tires are on the ground. I drove slowly and kept the engine reving at 2000rpms. The right side tires wer stoped thanks to ATRAC, and the left clawed as best they could to get the truck off its underbody and into the safespot. Wasnt easy either when you look towards your right and you see a huge drop. Anyway, enough of my rambling. Atrac 1 defined

BTW, I've also noticed Atrac in my 02 4r requires alot less wheel spin than my cousins 04 sport edition, and my friends 05 SR5.
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Old 02-08-2006, 12:01 PM   #12
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Default Atrac

Thanks for the info guys I appreciate it. Yes I have a center differential lock button. However, there was one time I was wheelin in snow and I got stuck in a rut in open differential. I locked the center differential to try to get out and my 4runner felt like it was going to break due to all these beeps and noises I think it was the Atrac. I did not want to force it so I had to dig my way out. Could I have pushed my 4runner a bit more to try and get out?
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Old 02-08-2006, 12:45 PM   #13
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First thing, ATRAC does not beep VSC does on the 4th Gens. It does make a bit of a racket by the brake booster as the pump and solenoids kick in. It can be unnerving, but once you are used to it it gives you a good indication when it start working. Sort a indicator that it is working. No problem in pushing it a bit when you do use it, dont worry too much about the noise.
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Old 02-08-2006, 08:42 PM   #14
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I Double Dog Dare ya to tell Shotts that.

Quote:
Originally Posted by LIFE_IN_4Lo
...All 120 platform suv's use Toyota's ATRAC II+
It is improved over the Land Cruiser 100 ATRAC II ...
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Old 02-08-2006, 09:55 PM   #15
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Quote:
Originally Posted by Dealmaker
I Double Dog Dare ya to tell Shotts that.

You can only talk to a brickwall for so long. I would like to see a 100s ATRAC in action before making a statement either way, but I believe the 100 does not have the dual sensors on each wheel like the 4R, etc has (sort of starts telling you something).
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Old 02-09-2006, 12:52 AM   #16
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Quote:
Originally Posted by bulldog

You can only talk to a brickwall for so long. I would like to see a 100s ATRAC in action before making a statement either way, but I believe the 100 does not have the dual sensors on each wheel like the 4R, etc has (sort of starts telling you something).
The 100s dont have the double sensors. One thing I do like about the VSC in the 4th gens is its not like the 3rd gens. The 3rd gens when turning into a fast paced street from a dead stop, usually inner tire breaks traction, VSC will kill the motor and makes u panic cuz power wont wake up tilll moments later. The 4th gen when I did the same moves, didnt hesitate at all. Just carried on what it was doing. On the 3rd gens, u must engage AWD if u wanna do such moves inorder not to endanger ur ass when pulling into a fast street lol.
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Old 02-10-2006, 03:05 AM   #17
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Default Center Vs. Rear Differential Locks

Does anyone know the difference between the center and rear differential locks on the 4runner and the Xterra's? I hear the Xterra's are very nice offroading. Are there any fans of them?
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Old 02-10-2006, 08:48 AM   #18
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I believe the Xterra has only part time 4WD (no center diff), so when you go into 4WD the center diff si automatically locked. You can then also lock the rear diff when going through tough spots. I don't know if the new Xterra has traction control. The 4R is full time 4WD so it has a center diff which needs to be locked when going through tough obstacles. The 4R does have a pretty good ATRAC system to help you through tough obstacles as it works on both axles. So it will really depend on the terrian to see if a rear locker only is better than ATRAC. I have wheeled with 3rd Gen 4Rs with rear diff locks and was able to go where they did with ATRAC. It does help to have a traction device on the front axle as well.

I have seen the new LR3s and RR in action and their traction control was the only one I have seen in person that is more aggressive than the 4Rs. I think the H2's traction control is also more aggressive. Both of these vehicles have settings for the traction control which allows the driver to make it more agressive for rocks and less for mud and sand. The 4R only has one setting so it can't be so aggresive, as it will hold it back in sand and other loose surface areas.

All in all ATRAC works really well once you are familiar with, but it is not as good as double locker. But ATRAC seems to work for most moderate terrian. Very aggresive rocks will be a problem however, but most vehciles are not capable of doing that terrian without serious modifications anyhow.
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Old 02-13-2006, 05:46 PM   #19
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Default Center and Rear

Do the 4th gen 4runners have center and rear diff locks?
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Old 02-13-2006, 06:14 PM   #20
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Quote:
Originally Posted by 4wdrunner02
Do the 4th gen 4runners have center and rear diff locks?

No, 4th gen 4Runner's have Torsen center locking differentials only. The third gen initially came with a rear locking diff, but then Toyota got away from that and added the center locking diff on the 2001 model year. I've had both, my974runner Limited had the rear locking diff, and it worked great. My mom's '01 4Runner has a center locking diff. Then of course, my034runner has the Center diff lock. They all work great.
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