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Discussion Starter #1 (Edited)
Does it work, Yes! How does it compare to A-Trac, only time will tell...

Intro:
All of you know by now that if you didn’t get an FJ with a rear Diff Lock, you automatically didn’t get A-Trac. Now surprisingly, the locker has nothing to do with A-Trac, its just that Toyota apparently thought that if you don’t need a locker you have no use for A-Trac ether.
Looking at the difference between a Locking FJ and Non-Locking FJ you will find only one difference that has anything to do with A-Trac, which is the Brake Computers Part Number (The one mounted to the Brake Booster).


All the wiring, sensors, actuators, etc… are the same because A-Trac uses the same system as VSC, ABS, and Trac. So the only difference is programming.
Now since Toyota has not released the Re-Flash for the Brake Computer (Dealer theory is just replace the unit) and a new Brake Computer is as much as a ARB Locker (If you have the money for a Air Locker, than by all means, go for it, I will… sooner or later) there is really no good way to get A-Trac. So my theory was converting Trac into a from of ‘A-Trac’, different problem, same end result…

Thanks:
First of all, let me say THANK YOU to some members who have helped without even knowing it; because of their previous research, posts and answering some questions, I was able to find a way to do this.
Thank You to: PRCruiser, Kansas Law Dog, Tranman, Homdad, and Tibaal89

Theory:
Trac is a from of A-Trac with one major difference: Trac only works in 4Hi (HL) and A-Trac only works in 4Lo (LL). Contrary to most peoples believes, Trac does NOT control RPM in 4Hi (HL), only in 2 wheel (H) drive.


Actually making Trac work in 4Lo (LL) is as simple as bypassing the 4Lo (LL) switch for the Brake Computer and ECU.

One question remains:
Does Trac control the front wheels or just the rear?
EDIT: After several tests, yes 4Lo-Trac does control all 4 wheels.

How:
The mod is actually very simple. All your doing is interrupting the ground signal from the 4Lo (LL) indicator switch to the Brake Computer and ECU, therefore making them think your still in 4Hi (HL).



Mod:
Look under the dash on the passenger side, you will see one of the main harnesses running through the firewall. Taped to it you will see a Blue Jumper (B45).


In this jumper are 3 White/Blue (W/L) wires, you need to unpin (or cut, or cut and put a switch in, which ever you prefer) the wire on pin 9.

EDIT: According to BlueMeanie it is better to have a switch because when in thick mud you need momentum to get you though so turning off 4Lo-Trac can be helpful.



If your looking at the wire side of the connector, with the release button on top, it will be the 3rd W/L wire (the one all the way to the passenger side). MAKE SURE you get the W/L wire on pin 9 if you get one of the other 2 you will have a X-Mas Light Dash!
That’s it! Your done!!!

To Unpin the wire so that this mod is 100% reversible, see post 23
http://www.fjcruiserforums.com/forums/1224220-post23.html

This is a picture of mine after the mod. I put a switch in line so I could test it, the brown wire goes straight into pin 9. The 'aftermarket' W/L wire goes to the wire that used to be on pin9. Hope that helps...



The way you know its ‘Engaged’:
Go into 4Lo (LL). Usually the car with the swirly marks will turn on, telling you that Trac is no longer active. If your in 4Lo (LL) and that light does not come on, the mod worked and you now have 4Lo-Trac. Trac will disengage when hitting the brake and/or clutch.

Obstacle Example:
In January of 2008 I attempted a steep hill climb on lose dirt, some rocks and large ruts. I got stopped at a point where passenger font and driver rear where just spinning. I tried for 30 minutes, different lines, but the truck just got into a worse position every time. So I gave up and backed down the mountain.
In December of 2008 I attempted the same hill climb, I again got stuck at the same spot, again same problem (2 wheels spinning). I then flipped my switch to turn 4Lo-Trac on, shifted into 3rd (seams to work better) and kept a steady foot on the gas. With some guidance of Homedad, the truck started moving, the brakes where engaging like crazy, my Trac light where blinking like crazy and the truck just kept on going.

Disclaimer:
I, this forum or anyone posting in this thread cannot be held responsible for any damage that might occur to your vehicle because of this modification. By modifying your own wiring harness you take full responsibility of any damage, injury, etc… that might occur.

UPDATE:
Post 73 from PRCruiser:

this is the video I made when I finished everything. You'll see a RR diff button but I dont have e-locker on my FJ. I have it there for a future ARB locker.

4LO hack using atrac button

 

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I'll try this on Monday (and not now because I have tonight the PR•FJ Christmas party and tomorrow I will attend to an obstacle event which one of our member will run) and as soon I test everything (if somebody tries is first, better) I will write the experience.

Thanks for not surrender on this "wondering" that is around 2 years of investigation.
 

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If this actually works (and I have no reason to doubt that it doesn't), you should be awarded the Forum Member of the Year!!!:clap::rocker::king:
 

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It DOES WORK kids....I Pumba surfed his rig up a climb last night that would have NEVER happened had it not worked!!!!:bigthumb:

Good job Dan!!!!

Pumba for Electrition of the year!!!!
 

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Great find. I am sure a lot of peeps are thankful for your work on this one.
 

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congrats on a mod well done!
 

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Sweet Dan, that's some thinkin there! So the only difference between trac/a-trac is potentially a-trac does all 4 and trac *may* only do two? I mean other than the stock configuration that only uses a-trac in 4L with people who have that option.

Second question.. What's up with the A-trac box in 4L with the locker engaged. It doesn't' say it operates but doesn't have a "-" either?
 

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If this actually works (and I have no reason to doubt that it doesn't), you should be awarded the Forum Member of the Year!!!:clap::rocker::king:
X2.

Very good info Dan! :)

Sean
 

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Discussion Starter #15
Thanks for the comments! I can't wait to hit the trails and test it some more. The holiday season is making it difficult but hope to get some wheeling in soon!

Sweet Dan, that's some thinkin there! So the only difference between trac/a-trac is potentially a-trac does all 4 and trac *may* only do two? I mean other than the stock configuration that only uses a-trac in 4L with people who have that option.

Second question.. What's up with the A-trac box in 4L with the locker engaged. It doesn't' say it operates but doesn't have a "-" either?

Yes, the only 'potential' difference is that it 'may' only work on the rear instead of all 4. This will take some more testing before I can say for certain. For now, all I can say is that this is an improvement from not having anything since I was able to tackle an obstacle that I failed on twice...

Also, I think that A-Trac is a little more aggressive but this will take some testing again. I hope to run a trail soon and get video of one FJ with A-Trac going through an obstacle and then me with the 4Lo-Trac. I'm hoping not to see a difference but I just don't know at this time.

I don't understand your second question, please remember that I have never driven an FJ with locker or A-Trac so I'm not following...
 

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Second question.. What's up with the A-trac box in 4L with the locker engaged. It doesn't' say it operates but doesn't have a "-" either?
Originally (prior to Nov 06 production) ATRAC and the rear locker couldn't be engaged simultaneously. After the change, the rear locker engagement would still allow ATRAC to work on the front axle. Prior to the change, locking the rear axle defeated the ATRAC.

I beleive the chart Dan posted was an original diagram before the change was made.
 

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I was there for the maiden voyage of the Trac test.....

Like Dan said....The rig was on a steep hill with moguls that put front right/rear left in the air.....We were going nowere.....

Then the mighty switch was flipped.....

We went up the hill no problem.....

The "trac" did in fact work....

It worked on the same system as the 2wd version....but it absolutely made the difference on the climb...which we made NO PROBLEM!!!

It is NOT full "A-Trac" per se.....it is not as aggressive as full A-Trac and my "guess" is that it was working on the rear only or it's just a different software program on the ECU....

Regardless....It worked....and it worked damn well!!!:bigthumb::bigthumb::bigthumb:

All future wiring on the Homedadmobile will be done by Dan.....:jester:
 

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Discussion Starter #19 (Edited)
Mike, you've driven my rig before, your more than welcome to it again :D Just leave my frame alone...:rofl:

Josh, now I get it, blame it on my German... RoverGGM is right, the diagram I posted is before the change. I don't have one for the newer models however the wiring is supposed to be the same so Toyota must have changed that in the programing. No matter what, this would not affect any non-locking FJs so this mod 'should' work no matter what year.

I'm agreeing with Homedad, I don't think its as aggressive as A-Trac but like I mentioned before this will take some testing to be a 100% certain.
 

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I have the same problem as this in the fact that I do not have A-Trac or a locker, and no money to add them so let me tell you any added traction I can get is greatly appreciated. I am doing this MOD ASAP, but i have a problem understanding it. I am not planing on running a switch to it and I do not understand what i am hooking the white wire to. Your post says to cut the or unpin the wire but I am not sure what to do with it after that. Sorry if it is posted and I am not understanding then pleaes let me know.

Oh yeah and thank you so much for finding this and putting in your time to not only do it, but to help inform the rest of us how to as well. That is a very cool thing to do. :cheers:
 
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