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2005-2008 4X4 TRD Off Roads - VSC/TRAC/HAC/DAC/ALSD/ATRAC explained

Discussion in 'Technical Chat' started by GP3, Oct 27, 2011.

  1. GP3

    GP3 [OP] Well-Known Member

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    David K did a fantastic job explaining the traction control features on the 2009+ TRD Off Road models.


    This thread is for the other guys. 2005-2008 4X4 Off Road owners. I've noticed there is a lot of confusion on this forum regarding the 2005-2008 4X4 Off Road models. More specifically, the traction control systems.


    Updated 2006-2008 ATRAC information.




    For now, forget about the RR Locker as I explain the electronic traction control(s).

    2005-2006 4X4 Off Road trucks have an optional package that equips the truck with VSC/TRAC/DAC/HAC/ATRAC. This system includes the infamous Hydraulic Brake Booster that 2009+ 4X4 TRD Off Road trucks have.

    05-06 trucks do NOT have a button to turn on or off VSC/TRAC/ALSD/ATRAC. These systems are on full-time. DAC is the only traction system button to the left of the steering wheel (It is only used in 4WD Low)

    The Off Road models have open front and rear differentials. This is less than ideal when off road. If one tire in the front, and one tire in the rear lose traction, you will go nowhere. TRAC simulates a mechanical Limited Slip Differential by braking the tire that no longer has traction. By doing so, it sends the power to the tire that does have traction. This allows you to climb right out of the low-traction situation.

    TRAC works in 2WD, 4WD High (ATRAC), and 4WD Low (ATRAC). It does not work with the RR Locker engaged. (There is a modification to allow ATRAC + RR Locker in 4WD Low if anyone is interested).

    In 2WD, brake and throttle modulation are used on both rear wheels when the tires break the limit of traction. In both 4WD modes, only the brakes (no throttle modulation from the system) are used when the tires break the limit of traction.

    HAC is Hill Assist Control. When facing up a hill in a forward gear and when brakes are released, the HAC will activate and hold the truck still for a few seconds. This gives you time to move your foot to the throttle without moving backwards down the hill.

    DAC is Downhill Assist Control. When facing down a hill in 4WD Low, you press the DAC button to activate. It will then send brake force to the wheels. A downhill cruise-control. If I remember correctly, at a speed less than 5MPH. It is advised to be in 1st gear (L).

    VSC is Vehicle Stability Control. It uses ABS and TRAC to 'assist', and 'protect' you from situations it thinks is beyond a humans control.

    2WD
    • Default: VSC and TRAC are on - Brake assisted limited slip.

    4WD High
    • Default: VSC off and ATRAC on. Brake assisted front and rear limited slip.

    4WD Low
    • Default: VSC off and ATRAC on. Brake assisted front and rear limited slip.


    2007-2008 4X4 Off Road trucks have an optional package that equips the truck with VSC/TRAC/DAC/HAC/ALSD/ATRAC. Like the 2005-2006 trucks, this system includes the infamous Hydraulic Brake Booster that 2009+ trucks have.

    All of the above applies to 07-08 trucks. With one exception. 07-08 trucks have a VSC/TRAC/ALSD/ATRAC button.

    2WD
    • Default: VSC and TRAC are on - Brake assisted limited slip.
    • Press once: Auto LSD - Brake assisted limited slip.
    • Hold for 3 seconds: VSC and TRAC are off. ABS is the only thing on.

    4WD High
    • Default: VSC off and ATRAC on. Brake assisted front and rear limited slip.
    • Hold for 3 seconds: VSC off and ATRAC off. ABS is the only thing on.

    4WD Low
    • Default: VSC off and ATRAC on. Brake assisted front and rear limited slip.
    • Hold for 3 seconds: VSC off and ATRAC off.

    ______________________________________________

    [​IMG][​IMG][​IMG]

    Attached are 2005-2008 Options lists from Toyota.

    P66Hn.jpg
     

    Attached Files:

  2. whippersnapper02

    whippersnapper02 Well-Known Member

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    Nice post man.
     
  3. David K

    David K Well-Known Member

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    WELL DONE!

    Q: On the 2005/6 Tacos you say: "(There is a modification to allow TRAC in 4WD Low if anyone is interested)".

    Then below that you say this:

    "4WD Low
    • Default: VSC off and TRAC on. Brake assisted front and rear limited slip without throttle modulation"
    Is that only if you do a mod?

    (My 2005 Off Road, which I thought had everything, did not have this option)

     
  4. GP3

    GP3 [OP] Well-Known Member

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    No. There is no modification needed for TRAC to work in 4WD Low.

    I edited the original post to clarify. The 'modification' I mentioned would allow for 4WD Low + TRAC + RR Locker.

    Unfortunately, your 2005 did not have everything like you thought. You were missing the VSC/TRAC/HAC/DAC package.
     
  5. GP3

    GP3 [OP] Well-Known Member

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    Added to the first post is a window sticker verifying the TRAC/DAC package (thanks BrettBretterson); hydraulic brake booster system from a 2007; buttons from a 2007. I'm working on getting a pick of a 05-06 button cluster.
     
  6. OffroadToy

    OffroadToy The dog did it...I swear!

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    Great post...Thankyou!! :)

    SSCN0217.JPG
    DSCN0341.jpg
    DSCN0344.jpg
     
  7. David K

    David K Well-Known Member

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    Yes, an excellent post... Now, watch out because if anyone prints it out and then gets stuck, Blue T will blame it on your ego! LOL
     
  8. GP3

    GP3 [OP] Well-Known Member

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    Thanks. It was a product of me having to know the ins and outs of everything I own :D. Also, your thread was a big help.
     
  9. David K

    David K Well-Known Member

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    I will double check your ABS with A-TRAC question... stay tuned!
     
  10. David K

    David K Well-Known Member

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    OKAY, just to confirm... ABS is off ONLY with the Rear Locked... Low Range only or A-TRAC only, there is no ABS Off light.
     
  11. GP3

    GP3 [OP] Well-Known Member

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    My thread title is too close to your thread! Those last two posts go in your thread.

    I'm going to change my title.
     
  12. David K

    David K Well-Known Member

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    Sorry, my bad! I posted it in my thread too, just now! LOL
     
  13. GP3

    GP3 [OP] Well-Known Member

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  14. GP3

    GP3 [OP] Well-Known Member

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    First post updated.

    2006-2008 Tacomas equipped with the TRAC/VSC package DO in fact have the extra special, oh so infamous ATRAC. Skip to the bottom half of this post to see.

    It's all in the name... Probably a marketing tactic from Toyota to make 2009+ trucks sell with an 'edge' over the previous models. We will never know.

    The only difference between the 2005-2008 (besides the VSC/AutoLSD button between 2006 and 2007) and 2009+ is that in 2009+ Toyota added a button that specifially turns on and off ATRAC. On 2007-2008 trucks, ATRAC is on by default when you switch to 4wd. ATRAC is turned off by holding the VSC/AutoLSD button (see first post). 2009 model also allowed ATRAC to run with the locker up to 3mph. Pre 2009 trucks need to perform a minor modification to allow ATRAC use with the locker.

    From the 2006 Factory Service Manual. Notice the explanation of ATRAC (Factory Service Manual now attached to the first post)(click to enlarge):

    [​IMG]

    You may ask how I know this is a 2006 Factory Service Manual. Note how this image (taken from the same 2006 Factory Service Manual) does not mention the VSC/AutoLSD button. Which the 2006 does not have (click to enlarge):

    [​IMG]

    Note how the 2007 FJ Cruiser Factory Service Manual does mention the VSC/AutoLSD button and ATRAC button. Which it does have. (click to enlarge):

    [​IMG]

    -Your friendly 2006-2008 knowledge base :D
     
  15. David K

    David K Well-Known Member

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    Awesome discovery!!
     
  16. GP3

    GP3 [OP] Well-Known Member

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    Here's another table showing ATRAC's availability. The table was intended to show the difference in braking systems between 08 and 09. The big change was the change to the base and Sr5 models (the addition of VSC, Auto LSD and TRAC).

    [​IMG]
     
  17. GP3

    GP3 [OP] Well-Known Member

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    I'm a little confused by that post, but we have discussed it before. Your 2005 truck was not equipped with the VSC package (like you mentioned), but it was indeed an option on 2005-2006. Check out this window sticker of a 2006.

    (click to enlarge)

    [​IMG]
     
  18. Crom

    Crom Time is precious; use it wisely

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    Great info GP3. It's nice to understand the history of things.
     
  19. GP3

    GP3 [OP] Well-Known Member

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    :thumbsup:

    It's still current info for those of us in 2005-2008 trucks. :)

    I'm just glad I can give a little back to the TW community.
     
  20. GP3

    GP3 [OP] Well-Known Member

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    Some more info I dug up for us 2005-2008 guys. More info to clear up the common misconception that ATRAC was only available to 2009 + 4x4 OR.

    As you can see, in 2009 an ATRAC switch was added, and an ATRAC light was added to the vehicle models with the hydraulic brake system. 2005-2008 OR models equipped with the VSC package have the hydraulic brake system; they have ATRAC.

    [​IMG]

    For the 2005-2008 OR 4x4's, ATRAC is on by default when in 4H or 4L. Holding the VSC switch (2007-2008) for 3 seconds will disable it. Why Toyota added a switch specifically for ATRAC when the VSC switch works just fine?... No idea. Guys like switches?
     
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