A-Trac or Locker

A-TRAC. As mentioned, it's almost like having front and rear lockers.

Wheelspin occurs when power to that wheel/axle from the engine produces more torque than the coefficient of friction between the wheel and ground can handle. The wheel breaks loose. A-TRAC helps manage this by braking the spinning wheel, sapping torque and allowing the coefficient of friction to take hold again.

4WD helps you gain more traction by sending 25% of engine power to each wheel rather than 50% to each rear wheel. You actually have less power/torque per wheel in 4WD, but this is why you have increased traction. The same amount of torque needed to move your vehicle is now spread amongst the surface area of four tires rather than two.

The rear locker really is largely superfluous with A-TRAC. It would still be useful for descent of slippery surfaces (sand/ice) if we didn't have DAC as well.

Honestly, the only real uses I can think of for it now are workjobs like stump pulling or getting the boat pulled up a slick algae covered ramp...and in those cases, 4lo + A-TRAC may be superior as well.

If I had to pick one, it'd be ATRAC...it's a pity "Rear Locker" sounds so much cooler...

 

This is straight from Toyota's Glossary of TRAC:
Traction Control (TRAC)
The sophisticated Toyota system is an all-speed design that utilizes both brake and engine throttle control. TRAC helps to avoid slippage of the driving wheels by slightly applying the brake on a slipping drive wheel and reducing the throttle to maintain traction according to the road surface conditions. The system eliminates the need for a subtle accelerator pedal operation and helps ensure vehicle control when starting or accelerating on slippery roads.


It blips the throttle, according to their literature as well.

I could be wrong, but I have essentially the same model, and there's no "TRAC" option on the DC ORs, you have the option to enable or disable VSC in 2h & 4h, and it's non-functioning in 4l but you can engage A-TRAC in 4l & use it in conjuction with the locker under 5 mph.

And this is from their build page on the OR models:
OF] TRD Off-Road Extra Value Package w/JBL® Satellite Audio [6] and Bluetooth® [15] (cost savings of $950) Includes Off-road-tuned suspension with Bilstein® shocks, locking rear differential, 16-in. alloy wheels with P265/70R16 BFGoodrich® Rugged Trail T/A tires, VSC [8] + A-TRAC with Hill Start Assist Control (HAC) [16] and Downhill Assist Control (DAC) [16] (on 4x4 A/T models, in place of standard VSC [8] + TRAC).

Which states that if you have VSC on the 4x4 models, you have that IN PLACE OF their standard TRAC (traction control) option. It uses more sensors and "works better" I presume than regular ol' TRAC.

So unless something's drastically different on the 2010 models (always possible) and they're not stating that in their own literature (less possible but still possible, yes), I have the same truck, and I can say firmly that there's no 4hi with TRAC, because it doesn't exist. There's only 4hi with VSC, which blips the throttle (and heck, so does TRAC for that matter apparently).

ONLY A-TRAC doesn't blip the throttle, from what I've both read and experienced first-hand with this truck.

 

Random Bob, TRAC is on in H2 and H4, and there is no engine output regulation in H4 with TRAC. Look again at my sig. and see that I never said A-TRAC on with H4... Only TRAC on... A-TRAC is on in L4 only.

Here is the tech page that shows you what mode TRAC and A-TRAC are in and when engine output is regulated.



Here is one that explains the switch operation for TRAC OFF (AUTO LSD) and VSC OFF (Open Differential) in H2 and VSC OFF in H4:



Re read my 9 modes, I think I got the data right... but I appreciate feed back to make it better! See my post in the Tech forum where all this and more ways iof explaining the modes is.

Thanks!

 

Not sure who you are asking or where you read that statement...

The rear locker will stay locked at any speed... It is recommended it only be used to get unstuck. The Active Traction Control (if on) will turn off once you are moving with the rear locked. Using them both together is counter-productive, at speed... If you are in L4 and want maximum traction, let the A-TRAC do what it is made to do... up to 30 mph... If you can go faster, you should be in H4.

The rear locker is old school (now), and will not permit easy direction control (steering) the way A-TRAC does. Keep the rear locker for emergency only IF the A-TRAC ever fails to get you unstuck (I kind of doubt it... but more testing needed). I am a big fan of the rear locker and would insist on it... until I had Active Traction Control and saw what it does!

 

What I said was that in my understanding of it — both in experience and per literature — is that they ONLY have VSC & A-TRAC, with VSC being a "TRAC" replacement on these models. Having said that & gotten it out of the way, what I was trying to say was that VSC blips the throttle in 4hi, and A-TRAC does NOT in 4lo. I wasn't trying to say I've engaged A-TRAC in 4hi.

And I've re-read it a dozen times, to me my interpretation is correct. How old is the info/images you posted? I know things change, hell 2008 models didn't have VSC in 4hi AND no locker+A-TRAC in 4lo, so I'm just trying to piece it together.

PS though, Locker's still better IMO ;-)

 

Bob, trust me on this... I had an '01 and an '05 before my 2010... all three were Off Road TRDs (4WD)... The 2010 in 4H is way different than the 2005 or 2001 in H4... It has TRAC (LSD) on normally. The difference in deep sand is like night and day! I went into great detail elsewhere on this forum.. do a search of posts by me to find it. To turn off TRAC in H4 you need to stop moving, and then press the VSC Off switch for 3-5 seconds (car with wavey lines below it). VSC and TRAC will both turn off and THEN you will have open differentials.

VSC uses TRAC to achieve stability (along with the other things it does)... It isn't the LSD, TRAC is. Now in L4, A-TRAC is different, stronger TRAC (LSD)... Just like in H2 there is AUTO LSD, a stronger LSD than standard TRAC in 2WD.

Please review the chart I posted above called 'DRIVE MODES', that chart is for 2009 and 2010 OR TRDs, like yours. The Toyota written manuals are terrible, and I don't care for the names they have given to these systems, but that's what we got to work with!

H2 you have TRAC (with engine regulation) /or AUTO LSD /or Open Differntial modes.

H4 you have TRAC (without engine regulation) /or Open Differentials modes.

L4 you have OPEN DIFFERENTIALS /or A-TRAC to 30 mph/ or Rear Locker/ or Rear Locker with A-TRAC to 3-5 mph.

 

^this


A-Trac in itself is essentially (Trac ) + (A-Trac in 4L). Believe it or not. BTW A-Trac stands for Active TRAC / The name itself even applies that you have trac.

Its night and day obvious, I dont know what your experience is you say that you tested, but have to question it. You seriously cant miss the fact that you have Trac funcitoning. You can see it, hear it, and feel it.

Watch the dash for the slip indicator light. That light is shared with VSC, but when VSC is activating it it makes audible beeping noise. If its flashing with no beeping and your not sliding...its cause TRAC. You can actually hear the relay's clicking when trac is working. And you can feel the obvious difference when its working. Turn it off and you will see.

VSC is not trac at all, nor is it some type of replacement as you have suggested. VSC is about vehicle stability. It uses steering angle sensor, yaw rate sensor and a G-force sensor. It has nothing to do with a wheel spinning (except with ABS and not spinning at all), it has to do with the truck sliding. Its not really a traction aid per say, its more of a stability and anti-sliding aid.

Believing what your window sticker says versus the factory tech service manual is your mistake.

 

It's all about wanting to learn... That's why I came here right after getting my 2010. I had no idea about these new traction features... The salesman couldn't explain them, the service man couldn't... You guys here in Tacoma World could... But, I was getting bits and pieces.

I made my 9 modes signature to put all the bits and pieces together in a short, easy essay. In the Tech forum, I went into greater detail with three different ways to describe the modes... check it out! HERE: http://www.tacomaworld.com/forum/te...uto-lsd-explained-easy-understand-i-hope.html

 

I have to assume sarcasm on the above post. Given the fact that this has been explained 10 times or so. In addition there is a chart that I posted from the Toyota Tech Manual, (reposted above) indicating TRAC operation, and when. It quite simply acts as a limited slip front and rear, in 4High. It's function does not relate to the VSC funtion. One is traction control (wheel traction) the other is stability control (Yaw & Polar Moment manipulation)
And VSC does not "blip" the throttle. Ever.

 

We sure try, don't we Hemi? LOL!

The only way he may figure out that he has TRACTION CONTROL (TRAC Limited Slip) in H4 is to hold down the VSC Off switch (while stopped) for the 3-5 seconds.... and to turn off VSC (and TRAC)... drive in a traction situation like deeps snow or mud or sand... or up a hill... then do it again with TRAC on (or vice a versa)!

It is night and day!

 

I have a 4x4 Off Road on order this is gonna be fun to learn.
And confuse me.

 

All things being equal, I vote to leave A-Trac enabled and lock the rear diff. In this mode, the rear will be locked and the A-Trac will take care of the front. The Tacoma is next to unstoppable that way.

We all win.

 

It is hard to tell if we are all on the same page with the data being provided, as there are at least a dozen threads on the understanding of A-TRAC (and the other traction choices we now have, 2009 +).

A-TRAC (Active Traction Control) is all you now need... It is doing the same job as lockers front and rear, but allowing for steering control that lockers don't give you.

Just push the A-TRAC switch once when you go into L4, and from then on, it will always be on when ever you are in L4... unless you push it again... That's it. (period)

On another thread (Drug airport) I took my Tacoma over some roads that I would normally engage the rear locker (this is my third 4WD OR Tacoma), and instead used A-TRAC, to compare. The traction abilities (using A-TRAC only) were superior to my previous Tacomas with the rear locker, in the same situations. I even high centered the back end on accident, and A-TRAC pulled me free. The rear locker would have been useless as both back tires were in the air.

In H4, the TRAC (limited slip system) works great and is far superior to the open differntials of before. In L4, the A-TRAC is superior to a locked rear and open differential in the front.

Naturally, the 'testing' continues... as I use the new truck more, I will let you know what happens... Hoping for a Baja trip next month (San Felipe 250 race weekend) for more deep sand trials!

A-TRAC has been around awhile... it is only new to the Tacoma in '09. It works!

 

YES indeed... but keep in mind, the A-TRAC will only be operating up to 3 MPH when the rear differential is locked.

There is not a constant, equal traction need at both rear tires... except maybe on a drag strip... just an occaisional need, but A-TRAC will give it.

I suggest (as does Toyota) to only use the rear locker if you should become stuck... which I am still trying to do using just the A-TRAC, and haven't succeeded, yet!

It is great that Toyota has elected to keep the rear locker on our Trucks, I am sure it is a reason people will buy a Tacoma TRD (it was for me)... But someday, once all Tacoma shoppers discovere how well A-TRAC works, I would bet it will be dropped. A-TRAC is just a better way to lock the tires for traction... and it works on all four tires... Real four wheel drive, that ain't no jive!

 

I was out in soft sand dunes this past weekend. I was in 4lo with ATRAC on. I honestly didn't even get to test it. Even climbing hills, it never gave me more than 1 click at a time.

As I posted earlier though, I have yet to see the locker do anything the ATRAC can't do by itself.

As David K said, testing shall continue. Maybe I'll go play in the slick rock this this evening or tomorrow. We've been muddy and snowy lately. I avoid mud like the devil.

 

David K, Perhaps my point was lost... I did qualify my post with the preface: "All things being equal."

Locked and A-Trac, there is nothing better for our stock trucks!

 

The more input the better!

However, could you tell me what this means: "Even climbing hills, it never gave me more than 1 click at a time." ??

In other words... it was good or bad? What does one click at a time mean. MANY THANKS!

By-the-way... try High Range 4WD (with TRAC on) in the sand before going to L4... just for grins.

I find that low range has too much torque, and limits your speed in the sand... although A-TRAC was great on getting me unstuck when I buirried the tires on purpose (by turning TRAC off in H4). Once out of the stuck, went back in H4/ TRAC on and cruised all over the beach.

 

10-4 on that... we have tractors for trucks! No need for expensive tires or aftermarket lockers!