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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. Nov 1, 2014 at 1:51 PM
    #1401
    js312

    js312 Well-Known Member

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    My understanding:

    The yellow wire mod gives you TRAC in 4-Lo. TRAC is not A-TRAC, nor is it as good.

    A-TRAC is very aggressive and works great at very low crawling speeds. TRAC needs to see more loss of traction than that to work, so you'd need to give it more throttle than you would A-TRAC.
     
  2. Nov 1, 2014 at 2:11 PM
    #1402
    33yrsoftoys

    33yrsoftoys Well-Known Member

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    Thank you js312, your answer actually asks the same question that I did, only in a statement. If a trac only works at very slow speeds and disengages above 3mph then it leaves open diff's. If the yellow wire mod works at speeds above 3mph wouldn't it be another drive mode option?
     
  3. Nov 1, 2014 at 2:15 PM
    #1403
    js312

    js312 Well-Known Member

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    I believe the 3 MPH limit only applies when the rear diff is locked.

    You had a statement in your last post about the yellow wire mod being "as good" as A-TRAC, which isn't the case.

    So, no, no point in TRAC in 4-Lo if you have A-TRAC.
     
  4. Nov 1, 2014 at 2:21 PM
    #1404
    33yrsoftoys

    33yrsoftoys Well-Known Member

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    I guess to explain my question better it would help to go back to the beginning of David K's original post. I hope this clarifies my question.
     
  5. Nov 1, 2014 at 2:25 PM
    #1405
    33yrsoftoys

    33yrsoftoys Well-Known Member

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    And to clarify further, is wasn't my statement on trac vs a trac, it was isitahemi's statement. He is the original OP that discovered the yellow wire mod for TW.
     
  6. Nov 1, 2014 at 2:27 PM
    #1406
    js312

    js312 Well-Known Member

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    I don't think there is a 3 MPH limit when the rear diff isn't locked, so that would make TRAC in 4 Lo pointless on an Off-Road.
     
  7. Nov 1, 2014 at 3:38 PM
    #1407
    33yrsoftoys

    33yrsoftoys Well-Known Member

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    I guess I'm confused. You said a trac works very well at SLOW crawl speeds. Now its under 3mph when the rear diff is locked? IF the rear diff is locked, when used with a trac, limits speed to 3 mph, would the yellow wire mod, with diff locked, offer a 10th option? Would it also limit the speed to 3 mph? Or would trac work for the front axle without speed limitations? David K has explained drive modes to many Tacoma owners, myself included, that's why I asked him?
     
  8. Nov 1, 2014 at 8:23 PM
    #1408
    js312

    js312 Well-Known Member

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    My first post says A-Trac works well at slow crawling speeds while TRAC needs more throttle to do much of anything. That's why it's not as good. My truck does not have A-TRAC, just TRAC. You really need to step on it to get the LSD functionality to do anything...at least in comparison to trucks I've driven with A-TRAC.

    I'm fairly certain A-TRAC works at any speed in 4-Low, but is limited to 3 MPH or less with the rear diff lock on.

    I suppose that what you're saying would work, but I don't think it would make any sense to do that mod to a truck with A-TRAC. I just can't imagine a situation where that would be the difference between getting out of somewhere and not. It looks like you have a sport as well, so it sounds like you are looking for a hypothetical answer anyway :)
     
  9. Nov 1, 2014 at 9:00 PM
    #1409
    33yrsoftoys

    33yrsoftoys Well-Known Member

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    I also have an 01 TRD off road. It obviously doesn't have trac or a trac. I've owned it since it was new, and there have been times where I wished I had a(little more up front). Especially in mud. I've used it's locker at speed, which still functions flawlessly. That's why I asked the question, since a trac with a locked diff has the speed restriction. I don't think that qualifies as hypothetical.
     
  10. Nov 1, 2014 at 9:12 PM
    #1410
    TacoBrah

    TacoBrah Well-Known Member

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    Did some tests today in my 2010 TRD OR.

    First was a semi wet but not muddy steep/long hillclimb. Best way to describe terrain would be loose clay/shale on top with clay type earth underneath. Tried 3 times in 4lo with Atrac only, no locker, and could not get it. First attempt with Locker + Atrac I got up it. Friends who had rear lockers but no atrac got up first try as well.

    Second spot was a rocky, rutted low angled hill climb where you are likely to have a tire in the air at some point. I used locker + atrac and got up it easily first try. Friend with locker no atrac had trouble and took multiple attempts/lines to get up. Then another truck with locker no atrac got it first try by better line/driving.
     
  11. Nov 2, 2014 at 6:59 AM
    #1411
    33yrsoftoys

    33yrsoftoys Well-Known Member

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    I think this helps clarify my original question. Again, not hypothetical.
     
  12. Nov 8, 2014 at 10:37 AM
    #1412
    David K

    David K [OP] Well-Known Member

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    Yes, great... please let me know if I can help... I have posted different ways to explain the process since we all read things differently.
     
  13. Nov 8, 2014 at 5:59 PM
    #1413
    33yrsoftoys

    33yrsoftoys Well-Known Member

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    Thank you David K, I live in mid Michigan. Lots of deep snow most of the winter and sometimes the only way to keep from getting stuck is lots of wheelspin, well in excess of 5mph. Getting all 4 to spin as close to even as possible makes all the difference. My 01 TRD offroad has the locker and there have been times when I sure could have used a little more out of the front tires working together. I'm entertaining an arb locker in my new TRD sport and was asking if the yellow wire mod, with a locker will work at wheelspin speeds well in excess of 3-5mph. I've understood that the TRD offroad with locker engaged with a trac on won't. That was why my question on another option. Thank you again for responding and I hope you can help.
     
  14. Nov 9, 2014 at 6:59 AM
    #1414
    David K

    David K [OP] Well-Known Member

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    With the rear locked, A-TRAC does NOT activate until you are UNDER 3 MPH... So, you will have three spinning tires until you get stuck (almost stopped) and then A-TRAC will 'lock' (match rotation) only the front tires so they rotate the same.

    Have you seen the You Tube of the FJ Cruiser in 'Sugar Sand' with A-TRAC on? All four tires are spinning together just as if it had front and rear lockers.
     
  15. Nov 10, 2014 at 6:53 AM
    #1415
    David K

    David K [OP] Well-Known Member

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    None that I am aware of. If you can drive highway speed, you probably don't need to be in H4. The VSC system is excellent at keeping the truck driving straight on slippery roads or if you make sudden steering changes. It feels like having 4WD on the way it corrects for over-steer.

    Do know that the Tacoma 4WD system is not "All Wheel Drive" as it has no third differential to allow for the difference in driveshaft rotation between the front and rear, when turning. So, IF you are in H4 on DRY pavement or hard surface, you may want or need to go back to H2 to turn the truck's steering wheel much.

    4WD is for traction when 2WD isn't enough to move you... off pavement or snowy/ icy pavement.
     
  16. Nov 10, 2014 at 7:02 AM
    #1416
    David K

    David K [OP] Well-Known Member

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    Yes it is... enjoy the added traction, security and safety of 4WD.

    H4 (4WD-HIGH) will do 90% of your off road/ slippery road needs. All 2012+ models will be in 'TRAC' mode normally in H4... this is 'light' limited slip (has engibne regulation).

    If you have tire spin in H4, then press the VSC button quickly (moving or stopped) to go to 'TRAC OFF' mode. This is the 'stronger' limited slip (no engine regulation)... and perhaps what to do if you are off road and not just slippery road driving.
     
  17. Nov 11, 2014 at 6:52 AM
    #1417
    outdoorgb

    outdoorgb (.)(.)

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    On my 2014, the owners manual states 62MPH max in 4H.
     
  18. Nov 11, 2014 at 4:58 PM
    #1418
    David K

    David K [OP] Well-Known Member

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    :bowdown:
     
  19. Nov 20, 2014 at 9:28 AM
    #1419
    jruba

    jruba Taco-N-Madre

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    I need to print this , great info thanks ..
     
  20. Nov 20, 2014 at 11:05 AM
    #1420
    David K

    David K [OP] Well-Known Member

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    Here is a condensed clean version, in a closed thread (so it would stay clean): http://www.tacomaworld.com/forum/2n...-controls-trac-auto-lsd-trac-rear-locker.html

    (link in my sig)


    HERE is one that includes the changes made in 2012:

     
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