A-Trac or Locker

This video, filmed in soft sand, shows that the A-TRAC system delivers torque to all four tires... true 4 wheel drive! Watch how he climbs the sand hill with fully inflated tires, slowly to show the tires spinning and kicking sand.

http://www.youtube.com/watch?v=_VHxslTiQug

 

Okay guys... like I think I said already, those that don't have A-TRAC can't really judge fairly. This is my third tacoma... all three with the locker... and all were the best 4X4s ever... A-TRAC is just a complete new experience... and until you can try it, just a little, and see how amazing it works... then hold back your sour grapes.

In this You Tube, a dealer demos the A-TRAC on a Tundra that has three tires on roller pads (no traction) and one front tire on the ground, with a block in front of it.

Without A-TRAC (and even if he had the rear locked) the truck goes nowhere when the accelerator is pressed.

With A-TRAC turned on, and a little gas the truck (with one tire on the ground) moves and goes over the block!

http://www.youtube.com/watch?v=U1MOEZYAv5Q

The rear locker would not have done a thing... A-TRAC is just one more thing that makes our Tacomas even better!

Yes, you can have both the rear locked and A-TRAC on... A-TRAC strongly brakes a loose tire to the traction tire's rotation, forcing torque to the traction tire. The rear locker already has the two tires locked together.

You could do well on just A-TRAC from my experiences, so far. Toyota even tells you to use the locker only in a situation that nothing else works, 5 mph max... A-TRAC operates up to 30 mph and automatically goes off, and back on anytime you are in L4 (once the A-TRAC button has been pushed). A-TRAC doesn't affect steering and the locker does... It is a better system, but experiencing it is the only way you will appreciate it.

 

I have had my True Track in for 12k , I love it....

 

Look how much gas he had to give it before the tire driver front on the wheels "locked up" and transferred torque to the passenger front. And when it DID grab, it was jerky, not smooth.

You say a locker wouldn't help in this situation, and luckily you specify on THE REAR so you are correct, but if the front was locked, it would have gotten over easier, smoother, and better.

Locking the front *IS* and option, I'm doing it on my '02. Lockers ARE better. It's not that A-TRAC is worthless, it's just that a locker is better for this particular task.

From someone who has A-TRAC and a locker on an '09, and decided to backtrack to an '02 and get fully locked.

 

ok so the end of the thred.... for crawling i know a locker will out perform on rocks sand and mud. now for snow and ice!!! a locker is no good at all its fun but not great on ice thats where the other doo hicky comes in for great use lockers are dangerouse on ice when you are trying to just drive if you are messing around thats a whole nother ball game if your a good drifter.... fast offroading in sand would be good with the a-trac because it can stop a wheel frome sinking in the sandy uphill to get you stuck but if ur locked with ur foot slammed on the gas and have no intention of slowing down go for locker lol just depends on what you plan on doing with it probibly why they came with both!!! im locked front and rear ice is a blast for me!!!!

 

they cant! dont mean to sound like an ass but if your locker is on the a-track is pointless for the rear because it will slow down both rear tires regaurdless what side hence LOCKER lol locks in both tires... abs a-trac is useless if you think about it with the locker on. only good for the front but might get you stuck if its slamming the breaks on the rear axle compincating for one side will slow you down..... sucky!

 

Thank you Bob,

However, the front tire in the Tundra video was blocked to not move... and yet it still climbed over the block... even though the other three tires were spinning (like on ice/ mud/ sand)... So, sure it looked jerky. By the sound of it, it was an employee in the video who had never practiced it before, either. The FJ Cruiser in the sand showed no jerking at all (because none of his tires were blocked).

None-the-less, the A-TRAC is included in our Off Road 4X4 Tacomas and front lockers are not. Steering is not affected by A-TRAC either.

When I was using it around the 'Drug Airport' there was no jerking at all... It was in L4, and the A-TRAC was on the whole time and only activates with a loss of traction. Lockers are not 'smart', and are on all the time requiring the driver to constantly engage and disengage in order to have steering control... or wheel freely. Toyota says to only use the locker to get moving and to turn it off right away... no such warning with A-TRAC.

Remember this is my third Tacoma with a rear locker... I wouldn't have wanted it any other way... but I had no idea what A-TRAC was until after I got #3, read this forum, took it to the desert, Baja, the snow, and the 'drug airport' hills of San Marcos. Now, I am trying to find a situation where I will need the rear locker instead of just A-TRAC.

A-TRAC (L4) is like having self-activating lockers and TRAC (H4) is like having self-activated limited slip.

Happy wheeling!

 

A-TRAC and the Rear Locker can be on together, but only to 3 mph... this is to make sure you move out of a stuck, I believe. If you can go faster than 3 mph (remember you are in 4-Lo) then the A-TRAC goes off automatically (if the rear is locked).

Toyota says to not go faster than 5 mph with the locker on... but A-TRAC stays active to 30 mph (with the locker off)! That's about as fast as you would want to go in low range, anyway... So, have A-TRAC on when you are in L4... IF you do get stuck, then you can lock the rear to get unstuck... and then turn off the locker (per Toyota manual).

I don't think the rear locker adds anything the A-TRAC doesn't already do and that Toyota left it on there as a selling tool... since all of us who love the locker, would be real upset at Toyota for dropping it. The locker could also be left on it as some kind of emergency back up, should you have brake/ A-TRAC issues?

Frankly, after watching both of those videos and using it myself... I don't see where the locker adds anything, as A-TRAC does it all.

 

ATRAC is NOT good for sand, as it brakes your wheels. Any braking = loss of momentum at that wheel. As all four wheels are touching sand, that means it's making the braked wheel act more like an anchor. Locker is better in sand & mud for this reason. It will work, and definitely better than just two open diffs, but since you're constantly in a state of wishy-washy traction in sand, you chance overheating your braking system quicker.

No you're not thinking correctly. They come with lockers in the REAR only. ATRAC is a 4-wheel system. So when you activate the locker in the rear, and the wheels are 'locked' to spin at the same rate no matter what, all it really does is prevent ATRAC from braking the rear wheels. The front diff is still open, and ATRAC can work on those cross-axle tires just the same as it could before, therefore there most definitely IS a use for ATRAC when the rear is locked — to transform your FRONT axle into an LSD.

…It's just a pity Toyota limits its use to under 5mph…

The video had THREE wheels on rollers: both rears, and the driver front. because if BOTH fronts were on pavement, it wouldn't have tested ANYTHING. For the experiment to be valid, THREE wheels were on rollers, and when ATRAC was activated, it braked the DRIVER'S front (on rollers) to account for the difference in wheel speed between it and the planted, stationary Pass. front. This transferred torque to that wheel, causing it to drive over the block.

However, it was not a smooth, controlled motion. It was jerky. Also notice how long they had to gas the truck before that wheel moved. The rears (and presumably the driver front we can't see) spun a handful of times before the truck even attempted to compensate with braking force. With a locker, he could have just 'feathered' the throttle over the block, and had almost NO wheel spin at all, at ANY wheel. The rears rotated two-three times, on the trails that's a fair amount of damage to the track. Also, those rotations might just throw out the ground you were trying to get gripped onto, in the first place, putting you in a worse spot!

I think the locker adds a locked rear, which ATRAC cannot do. It fakes it by overuse of the braking system. Also, don't be fooled: a locker splits torque 50/50, ATRAC is at best 60/40 while the wheel is actively being braked, I'm willing to bet the actual split is a bit less than that. It's definitely a GOOD system, but it's not a locker. If you're actually using the truck to go off road, like me, building the truck to be your 'expedition' vehicle or whatnot, the locker is going to work better on the axle, because you're not braking wheels, you're powering them. Brakes=loss of power. If you're in sand or mud for instance, where the wheels are definitely IN or ON something but the ECU detects wheelspin and starts braking, then you're a) dragging a braked wheel a short distance, and b) chancing overheating your brakes, since continuous driving in those circumstances will cause continuous activation of ATRAC.

With a locker all you're putting to the wheels is power. That can be a big difference.

ATRAC is great in that it actually works on the front, FROM THE FACTORY. It's like a faux locker from the factory. That's awesome in its own regard. However, it's not quite a locker still, and not quite as good. If you're building a truck to be superb off-road, you add lockers, not ATRAC is my point.

I'm not debating whether ATRAC is GOOD, just pointing out that if you can, if you're building it, and you want it to be the best truck it can be off-road, you lock that bitch front and back.

 

I have a question. After all the discussion, I was thinking about that statement I wrote (quoted above). I understand A-TRAC well, but it never occurred to me to consier A-TRAC a "LSD type system."

What do you guys think about that. For the purposes of classification, is A-TRAC a type of "LSD traction system?"

 

i am thinking corectly.. if you have a locker ingaged and the a-trac is thinking one tire is off the gound in the rear because your slipping the rear tires in sand it will try and apply break to one of thoes rear wheels.... if it does it will be applying breaks to both wheels because the locker is ingaged it breaks eaither one both tires will slow down no matter what.. why do you think toyota made a-trac dissingage when over 5mph with the locker on? to protect the driveline and brakes when tha a-track thinks your truck is slipping. lots of stress on the rear driveline...

 

Yotabeast, I am afraid randombob is correct.

If you engage the rear locker and A-TRAC is still enabled. His point was that A-TRAC will only work on the front diff and not in the rear in anyway.

Toyota will not allow the systems to interfere with each other.

 

i dont belive for one second that a-trac cut off the brakes to the rear when locker is ingaged or els they wouldnt have limited it to 5mph is what im saying witch makes the locker ussless if a-track is on and poses a problem with speeds over 5mph.... in awnser to the first ? someone asked is their a mod so we can run both over 5mph... would not be helpfull

 

For arguments sake, I'm inclined to agree with randombob on this point.

Even Toyota's own demo's recommend the locker in deep loose sand.

http://www.toyota.com/vehicles/2010/fjcruiser/demos/rear-locking-differential.html

I would like to debate this point for academic purposes

You stated that you have overwhelmed A-TRAC, effectively by overheating the brakes. Not only in mud, but ice and snow too. You make it sound like it's an easy thing to do.

I just do not see this happening.

Since A-TRAC only operates at 5mph or less, It should not generate enough friction to reach the thresholds necessary to initiate actuator protection.

Furthermore, in my possession I have the 2009_Brake.pdf file which contains very accurate technical documentation. It contains a section dedicated to Auto-LSD and there is a precaution statement for continuous use of AUTO-LSD mode. Here is how that reads:

But it says nothing on the subject of continuous A-TRAC operations!

I draw my conclusion by the fact that Auto-LSD mode operates at much higher vehicle speeds therefore potentially generating greater friction in the brake system which translates to more heat.

I just do not see A-TRAC being overwhelmed that easily. I'm not saying it can't happen, but it should be extremely rare if ever!

 

i do agree with what you are both saying i just dont think you get my point... point is Toyota A-TRAC does not turn off the A-trac to the rear tires when the differential lock is on. its a full time system for all 4 wheels. witch means that your overheating your rear brakes because of the locker and the power to the opposing wheel. senario going up a sand hill slowly with A-trac and locker on such as in the video, A-trac will adjust for the front tires to regain traction if both of the fronts are pulling at a diffrent rate than the rear the A-track will apply the brakes to one or the other side of the rear to try and regain traction. The problem is that when it apply's the brakes to one side of the rear its going to be a shouting match between the motor and the brakes. both sides will turn no matter what because of the locker witch in short makes A-track usless... and harmful to the brakes if you got your foot in it... That is why toyota cant use both systems at once.. just throwing that out their to see if someone understands what i mean or if im just loosing my mined lol!

 

ATRAC is activated by variation in wheel speed across the same axle. Therefore if the rear is locked it simply won't activate. When one wheel starts spinning in excess relative to the others, brakes are applied to that wheel, without limiting throttle. That's also why you can "drive through" ATRAC by using to much skinny pedal and negating the effectiveness of the brakes.

ATRAC does over heat, alarm sounds, and system disables. It's the most brake activity short of repeatedly slamming on your brakes or doing a brake stand. It's well documented on the 4Runner forums that have been running ATRAC for years before tacomas got them.

 

I love ya, David, but you're wrong on this one. When ATRAC is on, the computer only compares the front right wheel speed to the front left wheel speed. It separately compares the back right wheel speed to the back left. It does not compare front to rear.

If my rear axle is locked both sides spin the same speed whether they have traction or not. Since both the left and right are spinning the same speed no matter what (it's locked), the ATRAC does not kick in on the back.

The computer will still be comparing the front left and right wheel speed and activate if necessary.

 

Let's remember that we all want the same thing... TRACTION!

A front locker is not available from Toyota, the A-TRAC is... I am not diss'ing the idea of a front locker... I am telling you that the sysytem Toyota has given us is incredible (compared to open front axles, as before). It works... I got unstuck twice now... once in deep sand (yes A-TRAC works awesome in sand to get unstuck) and once on an uphill grade with my back tires off the ground (like that Tundra demo video simulates).

So, while front and rear lockers may give superior four wheel traction (in straight driving), that just isn't a Toyota option.

A-TRAC works by my experience and others, who have actually used it, not just read about it... It works in all traction situations and doesn't affect steering! Thank you Toyota!

If you got the bucks... and want one more traction choice (to go with the nine we already have).. the get a front locker!

Another video of the A-TRAC working the front axle... the driver keeps his FJ over a ditch that puts is front left tire high in the air... The tire in the air turns the same as the tire with traction on the other side... just like a locker would... the two front tires are 'locked' together... the loose tire isn't 'just' braked as some think A-TRAC does... it isn't a limited slip action... it is closer to locker action...

http://www.youtube.com/watch?v=8la3t22W88E&feature=player_embedded

 

well if the computer just doesn the front left and right and the rear left and right i compleatly understand i thought it was going to be the same as let say the H1 computer and run out and moniter on all 4wheels.

 

but its ok cuz im locked all the way around i guess ill stick to the old school way fuck this computer shit lol