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A-TRAC/TRAC/AUTO LSD Explained (Easy to understand, I hope!)

Discussion in 'Technical Chat' started by David K, Jan 19, 2010.

  1. Mar 21, 2017 at 4:48 PM
    #1361
    David K

    David K [OP] Well-Known Member

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    Sorry I wasn't clear, I have never used the eBrake BECAUSE I have A-TRAC and it does the braking automatically and on just the tires that slip. I see no reason that it wouldn't help, it is an old trick.
     
  2. Mar 21, 2017 at 4:59 PM
    #1362
    sddarkman619

    sddarkman619 Well-Known Member

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    well if normally a-trac is turned off in 4LO then it shouldn't work. Right?

    but with the yellow wire mod it will work.

    what I'm trying to figure out is if it's really wokring when I am in 4LO and i put the brake on a little, if it's really doing anything or I think it's helping.
     
  3. Mar 21, 2017 at 5:08 PM
    #1363
    bski22

    bski22 Shaka Zulu \000/

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  4. Mar 21, 2017 at 5:20 PM
    #1364
    David K

    David K [OP] Well-Known Member

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    A-TRAC is selectable (on or off) and it only works if there is wheel spin (ie. only when you need it). I naturally always have the A-TRAC in the on mode when in L4. There is NO advantage to not use it. I don't want my tires spinning, because that would mean I have no traction.

    The yellow wire mod lets the TRAC system work in L4, that's all. Use the eBrake partially depressed to help slow tire spin, IF you don't have any of the fancy systems. Be warned, you are wearing the brake pads and shoes by using the brakes when there is no spin.
     
  5. Mar 21, 2017 at 5:23 PM
    #1365
    bski22

    bski22 Shaka Zulu \000/

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    I keep hearing about this yellow wire mod. Not sure if I'm going to drink the kool aid on that one. Running SR5 Model has its disadvantages until locker install
    And re-gearing. But I'll have to read all 68 pages to figure out if it's worth the hype.
     
  6. Mar 21, 2017 at 5:29 PM
    #1366
    David K

    David K [OP] Well-Known Member

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    This thread is not about that mod... Read the 4Lo Trac Mod thread.
    It is for the non-Off Road 4x4s that have nothing in L4.
     
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  7. Mar 21, 2017 at 5:32 PM
    #1367
    bski22

    bski22 Shaka Zulu \000/

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    It's all so confusing though o_O
     
  8. Mar 21, 2017 at 7:36 PM
    #1368
    sddarkman619

    sddarkman619 Well-Known Member

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    Again, I think you are missing my question. A-TRAC DOES NOT normally work in 4LO unless you have YWM correct?

    So Normally is no YWM there is no A-TRAC in 4LO correct?
    So if I don't have the YWM in my truck, trying the e-brake in 4LO will do nothing but slow me down correct?
     
  9. Mar 21, 2017 at 11:01 PM
    #1369
    sddarkman619

    sddarkman619 Well-Known Member

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    So does the Yellow wire mod enable VSC and A-TRAC?
    A-TRAC being it slows the wheel spinning and the engine output?
    or does it only do the wheel spinning adn A-TRAC is off.(engine output)?
     
  10. Mar 22, 2017 at 7:07 AM
    #1370
    Cold_Toad

    Cold_Toad Well-Known Member

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    The YWM has nothing to do with A-TRAC, A-TRAC is it's own separate thing and only available if you have an Off-Road.

    Without the YWM in 4lo you have open diffs, with the YWM it allows your truck to use limited slip in 4lo instead of just 4hi.

    https://www.tacomaworld.com/threads/4low-trac.51946/ Read this thread, has pretty much everything you need to know about the YWM and what it does.

    Using the e-brake with or without the YWM can help send power to the wheel that has traction at the cost of wearing out your e-brake.
     
  11. Mar 22, 2017 at 8:25 AM
    #1371
    David K

    David K [OP] Well-Known Member

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    What Cold_Toad said...

    A-TRAC is its own animal, it requires the hydraulic brake booster. All Tacomas (EXCEPT the Off Road TRD 4x4) have a vacuum break booster.

    TRAC is a limited slip system. A-TRAC is a no slip system that is more closely matched with front and rear locking differentials.

    The Yellow Wire (4-Lo Trac) Mod allows TRAC to work in L4, not A-TRAC.

    TRAC (limited slip) is not as mighty as A-TRAC (no slip) but is better than no TRAC (all slip)!
     
  12. Mar 22, 2017 at 8:47 AM
    #1372
    David K

    David K [OP] Well-Known Member

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    Exactly... and Toyota used some poor name choices which does not help.

    Here are the levels of traction, in my opinion, from least to most. Only the Off Road TRD has a locking rear differential and only the 4WD Off Road TRD has A-TRAC (and MTS/Crawl in 3rd generation):

    1) 2WD VSC OFF = No traction control (stop, press and hold in VSC button 3+ seconds).
    2) 2WD TRAC = Limited slip through braking and engine regulation to reduce tire spin. [Standard Mode]
    3) 2WD AUTO LSD = 2WD limited slip through braking of non-traction tire (quick press of VSC button).
    4) 2WD Rear Locker = 2WD Off Road TRD only. Both rear tires get 50/50 power split, even if one has no traction.
    5) 4WD-HI, VSC OFF = No traction control (stop, press and hold in VSC button 3+ seconds).
    6) 4WD LOW RANGE = No Traction Control. [Standard Mode]
    7) 4WD-HI, TRAC = Limited slip through braking and engine regulation to reduce tire spin [2009-2011 had no engine regulation].
    8) 4WD-HI, TRAC OFF = Limited slip through braking of non-traction tire (quick press of VSC button). [2012+]
    9) 4WD LOW RANGE + Rear Locker
    10) 4WD LOW RANGE + A-TRAC
    11) 4WD LOW RANGE + A-TRAC & Rear Locker
     
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  13. Mar 22, 2017 at 2:26 PM
    #1373
    bnv

    bnv Boy I say, use CRAWL to sneak up on that dawg!

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    More info/addendum maybe:

    To engage A-TRAC (4WD Low Off Road TRD 2016+ Only) - Press the MTS button and use the selector knob to select the type of terrain.


    Disclaimer:

    I speak with the easy assurance of the unconsciously ignorant.
     
    Last edited: Mar 22, 2017
  14. Mar 22, 2017 at 4:20 PM
    #1374
    David K

    David K [OP] Well-Known Member

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    Yes! 2016+ automatic trans 4x4 Off Roads have MTS (Multi Terrain/ Multi-level A-TRAC) instead of one level A-TRAC.
     
  15. Mar 28, 2017 at 5:54 PM
    #1375
    bnv

    bnv Boy I say, use CRAWL to sneak up on that dawg!

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    David K - Guru of Tacoma traction modes,

    Thanks for all the great info in this thread.

    My question:

    When would "engine regulation and braking" be desired vs just "braking"? Seems like engine regulation would generally be undesirable.

    Where would I use engine regulation off road as an advantage in my 2016 4x4 Off-road TRD?
     
  16. Mar 28, 2017 at 6:29 PM
    #1376
    David K

    David K [OP] Well-Known Member

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    Not at all.

    My 2010 has no engine regulation in H4. They added the regulation in 2012 with a button push to get the traction control without regulation, called TRAC OFF.

    In preventing wheel spin, by controlling the throttle (backing off the gas) you reduce the spin caused by too aggressive driving.
     
  17. Apr 30, 2017 at 11:24 AM
    #1377
    kcox31Tx

    kcox31Tx Well-Known Member

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    Question for y'all.
    I'm driving in town a lot and have been messing with the LSD on/off (2WD Auto LSD, 2017 Gen 3) using the VSC switch. I find that my truck drives a lot smoother (it's not rough riding or anything) but overall feels better when it's on. Does it matter if I'm making my daily trips with it on?
     
  18. Apr 30, 2017 at 11:53 AM
    #1378
    David K

    David K [OP] Well-Known Member

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    The manual doesn't recommend it (fear of overheating the brakes) but in reality, if you are on dry pavement there will be no excessive braking for traction. I can't image why AUTO LSD mode changes how smooth the truck drives, weird?
     
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  19. Apr 30, 2017 at 11:58 AM
    #1379
    kcox31Tx

    kcox31Tx Well-Known Member

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    Thank you. I appreciate it.
    I know. Its weird. I can't explain it. Might mess around with it more this week.
     
  20. Apr 30, 2017 at 12:00 PM
    #1380
    David K

    David K [OP] Well-Known Member

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    In AUTO LSD, the VSC is turned off under 30 mph... but if a dangerous swerve occurs, it will come on automatically.
     
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