Mods - ATRAC & Locking rear dif in other than 4L
 

I'm loving my T4R TE, but am somewhat annoyed about the limitations of ATRAC & the locking rear diff. Specifically, you must be in 4L to use either of them, and to use them together you must be going < 4 mph. That's fine for rock crawling, but not much help in mud or sand. There are a number of mods posted on other boards to get around these same issues with Tacomas and FJ's. Has anyone had tried these mods on the T4R? Armed with the 2010 TE wiring diagrams, I hope to experiment in the coming weeks.

These are the related links:

Rear Locker + ATRAC - Write up - TTORA Forum

The "No Cut" A-TRAC + RR DIFF Hack. - Toyota FJ Cruiser Forum

Traction Control (ATRAC hack) writeup! - TTORA Forum

thinking on the fly here-
the rear locker mod has been done for years, AKA Grey wire Mod., and is a good one- very useful, safe, and prudent to traction. Shouldnt seem to be too much to figure that one out if its being done on the newer FJ. I have a limited :( no rear locker stock.

Modding the atrac to work at higher speeds- Isnt it a braking traction control as in it applies brakes to one wheel to allow more power to other? That may not be the safest thing to have happen on a hard surface or even worse a slippery one. Not to mention the last thing i want in the mud is my brakes on- its all about more HP to the ground.
Again, im oldschool- flip the arb switch and lock the hubs. all this atrac, dac, kdss, hell even the center diff full time 4x4 i am still trying to figure out.

Glad to see you are forging new grounds and look forward to seeing how it works- maybe i will do some reading and jump in with you.

ok- this mod has to do with allowing the elocker and atrac to work simultaneously. Nice. too bad i dont have a rear locker. Must be possible with the 4R only cuz the FJ has the same technology?
Looks like the FJ crowd has it worked out, but i saw no mention of any 4H driving, it was only in regards to slow wheeling ATRAC with the locker engaged. Am i wrong?

I too would be interested in having the rear locker work in 4Hi on my TE. I can see it being beneficial in deep mud, sand, or snow(here in WI). No need for the ATRAC in 4Hi since it could cause problems and safety concerns as Zidaro posted above.

Please let us know what you come up with and if it works safely!

Brandon

My bad - I forgot one link. This is the "new & improved" grey wire mod for 2005+ versions of the Tacoma. Basically, it fools the 4wd ECM into thinking the truck is in 4L and will allow you to engage the rear locker in 4H, or even 2wd. From a quick read, I believe the T4R wiring harness here is very similar to the Tacoma. Looks too easy not to try.

Locker Mod- An Alternative - Toyota Forums :: Toyota Nation

I hear what you're saying about having brakes come on while offroading at high speeds. And yes ATRAC it would only engage a front brake if that wheel was spinning at a much higher rate than the other one, i.e., that you're losing traction to one front tire so ATRAC would try to slow its rotation to transfer power to the other side. Sounds to me like it would work ok in theory, but in practice it might not work so well. I'll try the locker mod first and see how it goes. The rear locker in 4H is a must have mod for me.

Amen brutha! Cant wait to have the locker like all the rest of my toys. Doit!!!!

Well I did it and it seems to work fine. It's really straightforward. There's a 4WD ECU behind the glovebox with an input from a switch on the transfer case that tells the ECU when you're in 4L. That input is the LIGHT GAUGE blue wire on the LARGER of the two plugs into the 4wd ECU, not to be confused with a heavier gauge blue wire on the second, smaller plug.

When you're in 4L, the transfer case switch grounds that wire to let the ECU know that you're in 4L, thus enabling ATRAC & the rear locker. So my solution was to rig a manual switch to ground that blue wire to fool the ECU into thinking you're in 4L, and then the locker & ATRAC will work in 4H. And it works.

You've got to pull the glovebox, but once you do the ECU is right there. I spliced into the blue wire, ran that wire to a switch, and the other terminal of the switch to ground. When I'm in 4H & flip the switch, the 4L light comes on and ATRAC & the real locker are enabled. Nothing to it.

Again, this mod only applies to the Trail Edition models - those with ATRAC & the locking rear diff. It's worked for me, but obviously, experiment at your own risk...


Diagram of what's where - 4WD ECU is #2, 4L switch is #4

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Wiring diagram

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Parts that have to come out to get to the 4WD ECU

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Where the 4WD ECU is located with the glovebox out:

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The mod:

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very nice! this one is on my list for sure! thanks!

Where, and what type of switch did you run? would you mind posting a pic of that? thanks.

Nice work, LWN.

Is there a reason they made the locking rear diff not available in 4H? Are there any concerns of it not being good mechanically for the system at high speeds? Is it just a fail-safe against accidentally driving on pavement with the rear diff locked, since it might be easier to forget you are in 4H as opposed to 4Lo?

Otherwise, this is definitely on my list as well:D

Sure - nothing special - just an $8 switch from DAP. I drilled a 1/2" hole into one of my switch blanks and glued it in. I'm actually not too happy with it because you can see the adhesive - think I may buy a factory Toyota switch & pigtail & use it instead.

<a href="http://s748.photobucket.com/albums/xx122/lnordmann/?action=view&current=DSC00204.jpg" target="_blank"><img src="http://i748.photobucket.com/albums/xx122/lnordmann/DSC00204.jpg" border="0" alt="Photobucket"></a>

As far as I know, it's a safety thing - to keep people from flying around at high speed or on pavement with a locked rear diff. I know this mod has been around for years on Tacomas - it was known as the "grey wire" mod, and I've never heard of anyone that's had problems with it.

And this one will go down in the annals of 5th Gen history as the
"LWN Blue Wire TE Mod"
Wow.....Great job!! :thumb3:
Where did you get the wiring charts and manual references?
Don't answer if you have to hunt me down and kill me afterwards.

Thanks, but my mods are lightweight compared to yours Harper :boink:

But I got all the diagrams & schematics on https://techinfo.toyota.com. It cost $25 for a two day subscription, $75 for a month I believe, but anything and everything you could want is available there. It's fairly easy to search the database too, once you get the hang of it.

The one thing my mod doesn't do is let you use the locker in 2WD. Although I'm willing to bet that if I also switched the black wire [which signals 4wd to the 4wd ECU], it'd work in 2wd too. But I'm not pulling the glovebox back out just for that. Perhaps someone else can experiment with it.

So is it possible to simply ground the light blue wire and not use a switch at all?

do you get a 4Lo light on the dash when u engage your switch?