A-Trac or Locker

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To Crom:

First & foremost, I'd like to go back a page and answer your question (or debate, maybe) of whether ATRAC is considered an "LSD" system.

I would say so of course (seeing as how I did ), simply because it allows for different wheels speeds across the axle to allow for better turning input, and also because the effective %'s it puts out when attempting to "lock" the axle, somewhere near 60/40 or so (like a good LSD system). However, even within the typical definition of LSDs, there's different systems that work differently. Some are clutch driven & some purely mechanical, some you can force lock-up with brakes, others are useless if a wheel gets off the ground, etc etc.

I'd say that ATRAC, while an "LSD" type of solution, is BETTER than an LSD, because it's open when most of the time you want it to be, and it's MORE useful off-road than an LSD. most LSDs, if you get a tire off the ground, they're shit. They turn into an open diff, and you have to fudge two or three pedals to get good performance out of it, and they only achieve their 60/40 split with traction at both sides (at least some). ATRAC though, even with a tire fully off the ground, will still achieve it's theoretical maximum torque split.

I know it seems like I've spent the last few pages bashing it, but it's a damned good system, it's about as good as a locker as you're going to get without actually being locked. I like it, I just want to specify that when it comes to "which is best" off-road, it's NOT a locker, it's merely 'close' to it; lockers are still king.


Now, to continue…

You're 1st assumption is that ATRAC only works under 5mph. this is not so, that limitation is only in effect whilst you have the locker turned on. Without it being locked, ATRAC works up to 40mph or so.

2ndly, if you're in sand/mud or something like that, going even just 5mph, as the ECU hunts traction it's braking the wheels OFTEN. Brakes heat up really fast, especially when the ECU is trying to brake the wheel that wants to spin the hardest that has power being actively applied to it, which is exactly the wheel it's ALWAYS trying to brake.

I can attest, if you're in a situation using the hell out of it, it'll turn itself off. TRUST ME. I've had it happen a few times. I have this truck. I've done it, especially in snow.


And for you clowns who skip to the bottom and don't read the posts (gotcha ), I am going to say it again: I like ATRAC, I think it's a good system, I think it's leaps better than a mechanical LSD, especially when you're off-roading. I just think/know that a locker works better across the axle. ATRAC is #2, Locker is #1.

 

The beauty of four wheel drive and low range is that you can climb without the need for speed/ momentum... Speed kills! Well, it just helps to break things...

Our trucks are not cheap.. and who wants to break them by hitting a hill climb at speed? The A-TRAC became available with last year's model (2009)... Unless you are rich, are you really anxious to break your new truck? If you want to do speed, then your truck needs to be prepped like a Class 7 Baja racer... with extra suspension, wheel travel, etc.

So, back to the beauty... Low Range 4WD is for crawling to get someplace we want to go... for fun or work. Before A-TRAC we had the rear locker... It was great for those really steep, rocky hills... I used mine many times (2001 and 2005 Tacomas). I still came upon conditions where I was stopped going uphill by a large rock and the tire(s) would spin... I had to get out, move a rock or use a spotter.

My 2010 with A-TRAC will not have that issue because both front (and both rear) tires will have torque if they have traction... no more spinning. The A-TRAC 'locks' the free tire with the traction tire with almost no differntial in wheel speed. Having a free no traction tire is rare... so using the brakes is rare... at least in most conditions I use it for.

If you look at the sand climb video, the A-TRAC powers all four wheels equally if all four have the same traction (or lack there-of). In the Tundra demo video, on the back axle... both tires were spinning (not braking) with the lack of different traction... again like the sand hill video. Only if one of the two tires per axle has different traction will one tire be braked to match the other.

The system is smart... it just doesn't brake spinning tires for no reason... In fact, it is giving us true four wheel drive... In loose sand before, tires not deflated, I would have one tire in front and one tire in the rear spinning and getting me stuck... the rear locker didn't change the movement, since the most weight in a pickup is over the front axle and with only one front tire spinning, it would dig in. A-TRAC in L4 or TRAC in H4 both keep my new Tacoma from digging in. I can drive deep sand without deflating the tires... the Sand Hill video FJ Cruiser also kept his tires at 32 PSI to show the spinning being equal across the axle.

As for STOCK factory traction provided on our trucks, A-TRAC is a better traction system than the rear locker from MY many experiences with the rear locker.

1) L4 is better than H4 or H2, for traction on steep hills.
2) The Rear Locker is better than the open differential, for traction on steep hills.
3) A-TRAC is better than just a rear locker in L4, for traction on steep hills.

and for the aftermarket fans, and to make peace:

4) Front and Rear lockers are the best for traction on steep hills.

Some rear locker in use photos of my last two Tacomas:



This grade I named 'The Widowmaker' back in 1999... It is on the road to Mision Santa Maria, in Baja California:









My friend had a new Land Rover LR-3, without a rear locker but with traction control:





I am looking forward to taking my 2010 A-TRAC Tacoma there!!!

More photos from that trip: http://vivabaja.com/msm

 

Thanks randombob. Having this discussion is very helpful. I guess I can say that I see it your way too now. A-TRAC to me seems would be considered an LSD type system.

I believe you on the A-TRAC overheating. Sorry if it seems like I doubted you. I was presuming it would be operated under 5mph. Also, I've come to rely too much on technical information... I pulled out my owners manual ('09), and on page 175, in the section on A-TRAC it clearly states:

• if the brake system overheats
  • The system will cease operation, a buzzer will sound and A-TRAC indicator blink to alert the driver. Stop the vehicle in a safe place (There is no problem with continuing normal driving) The system will be automatically restored after a short time.

Touche, and Thank you.

 

No problems man, and I thank you for being big enough to say as much. Hey, everyone makes mistakes or is wrong at times, hell I took information I saw @ the dealership and extropolated that ATRAC was a selling option on the 2008s, so I'm not perfect either.

For me, I just like to make sure people are arguing with the facts. ATRAC's not perfect, it's good, but we can't honestly debate what's better if we're unclear on how it works and what its limitations thusly are.

As an attorney, I'm sure you understand

 

I promiss to report if my A-TRAC ever fails to work, ever over-heats and shuts off, or ever fails to get me someplace that I would use the rear-locker before... This forum should report both good and bad... and from personal experience is best!

Thanks everyone...

 

X2

 

X3

 

We need to find a fix to make run the Atrac and the locker above 3-5 mph. I'm sure it can be done, it just need someone that have interest, documentation and time.

The following come from FJ Cruser forum:
http://www.fjcruiserforums.com/foru...tion-aids/17329-no-cut-trac-rr-diff-hack.html

PROBLEM: Early production 2007 model FJs (~pre-November 2006) do not allow A-TRAC to operate in conjunction with the Rear Differential Locker (RR DIFF LOCK) or vice-versa. The ECU allows only one or the other to be active, but not both.

WORKAROUND: Alex discovered a way to "fool" the ECU into thinking that the RR DIFF LOCK was always inactive by cutting the RR DIFF status wire coming from the rear, and applying +12v to it as it entered the ECU. From the ECUs perspective, +12v on this wire indicates that the RR DIFF is off. Since the ECU thinks the RR DIFF LOCK is off, it has no issues allowing A-TRAC to engage. Personally, I had issues cutting ANY wire on a factory wiring harness, much less one that is under the hood (exposed to elements) and connects to an ECU, so I looked for a different way.

SOLUTION After perusing the factory wiring diagram, I was able to track down the connector in which the RR DIFF signal joins the main engine compartment wiring harness. I surmised that by isolating this RR DIFF LOCK signal BEFORE it entered the engine compartment, I would be able to avoid cutting it at all. Subsequent testing has proven my theory, and I have modified 4 FJs (including my own) since then without cutting a single wire, or modifying the FJ in any way that is not 100% reversible. This modification is not difficult in the least, but DOES take a bit longer to accomplish than the Alex mod. Personally, I am able to complete it in less than 30 minutes, and for me, the extra effort is worth it for the benefits mentioned above.


Can someone is able to confirm if this mod will allow me to use Atrac & locker together on my Tacoma 2010.

Thanks