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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. Jan 30, 2016 at 8:15 PM
    #1301
    Metalnut

    Metalnut In My Kingdom Cold

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    Yes, your front diff remains "open" and the computer uses the brakes to create a tight LSD in the front when you use MTS. It does the same for the rear actually, but if you lock your rear diff, it's a physical locker and thus completely locked. So what you're describing there is #10 from the list above.
     
  2. Jan 30, 2016 at 8:19 PM
    #1302
    angry john

    angry john Well-Known Member

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    sweet i understand lockers from my time in a fj40 with my dad, but the new electronics are still a little fuzzy. Thanks for the help.
     
  3. Jan 31, 2016 at 10:14 AM
    #1303
    David K

    David K [OP] Well-Known Member

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    John, you have an AUTOMATIC... and in 2016, then automatic off road 4WDs DO have A-TRAC, but no button... it is incorporated into the MTS system (multi-terrain select).

    So, please go play with your new Toy and report back to us on the various terrain select operations.
    You should be able to notice that during loss of traction (when one or more tires spins) the spin will be halted as power is transferred to the opposite tire on that axle in a manner that BOTH will turn together... just like if a locker was on the axle.

    In A-TRAC, L4 driving, your truck feels like a Sherman Tank in that nothing stops it, not even if three of the four tires don't have traction! You should have the same feel in MTS or CRAWL... Just point the truck with the steering wheel and let it crawl over or up anything (that won't cause damage of course)!
     
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  4. Jan 31, 2016 at 10:21 AM
    #1304
    David K

    David K [OP] Well-Known Member

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    Right... so DO NOT use the Rear Locker as a first choice, as it will limit the traction features unless you are under 3 mph/ or stuck. The Rear Locker is for EMERGENCY unstuck (per Toyota) and yes, I know it works all the time in L4 if you turn it on. The point is, you should not need to... keep it as you ace in the hole IF the normal traction features (which do not hinder steering like a locker does) fail and you do get stuck. Since A-TRAC, I have never been stuck or needed the Rear Locker... I only use it to test it and see what it does differently than A-TRAC alone. Remember, I owned two other Rear Locker equipped Tacomas before the A-TRAC Tacoma, so I am very familiar with locker use.
     
  5. Mar 18, 2016 at 11:18 PM
    #1305
    tacogeorge

    tacogeorge Well-Known Member

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    Love it! About a week after I bought my truck I spotted a power line access path going up a decent sized hill. I was on my way to a friend's wedding and had a fresh hot coffee in hand but I couldn't resist my first off road opportunity in my shiny new taco. It was a slick stone base with 2-4 inch rocks covering it. My Inclinometer thing pegged at 30 going up. Wouldn't do it in 2wd in any mode. 4hi was getting me there and I think I could have made it but I wanted to play with all the modes. 4lo made it cake but would still slip a bit on the loose rocks. Crawl control was awkward. Pretty jerky (almost spilled my coffee!) and lots of noises, but effective. MTS was the magic maker though. I set it to loose rock and it crawled up and down the hill effortlessly. I didn't mess with the locker or the ect power but from what I understand the ect power just allows the engine to rev higher before it shifts. Love this truck! I'm going out to play all day tomorrow so I'll try to mess around with all the different modes. :burnrubber:
     
  6. Mar 19, 2016 at 8:45 AM
    #1306
    David K

    David K [OP] Well-Known Member

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    Thank you so much for your report! Would you please continue "testing" the new truck in a variety of traction modes as you did. I did all that back in 2010 with my (then) new Tacoma and it was appreciated by others not familiar with A-TRAC and the other traction gizmos. My truck is now 6 years old and still won't get stuck, lol!
    I would appreciate it if you could describe each MTS mode choice and after you try it, how it operated.
    Many thanks!
     
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  7. Mar 19, 2016 at 8:06 PM
    #1307
    tacogeorge

    tacogeorge Well-Known Member

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    No problem! Had a chance to try out mud/sand, rock, and loose rock MTS modes today and played with crawl mode some more. First time really getting her dirty. Had a blast!

    Mud/sand allowed quite a bit of wheel slip compared to the rock modes. I didn't have somone with me today in case I got stuck and I'm not quite ready to sink my shiny new toy up to the frame in mud anyway, so I stayed out of the deep slop. I probably didn't really need 4lo much less MTS for what I did go through today but I went ahead and tried it out at a fairly sloppy portion on the trail. It went through with ease. Allowed some wheel spin but didn't get sideways in the turn. I'll have to play with this one some more when I'm willing to risk getting stuck.

    Loose rock allowed just a little bit of slip occasionally. It was just enough to kick out some of the gravelly stuff and allow me to keep going. It was the most appropriate mode for the day. Lots of 20-40 foot tall climbs with a few maxing out the inclinometer on the dash (it goes to 30) and all on loose rocks from gravel sized up to about 4 inches. I only had to back down one hill today. It was well beyond 30 degrees, getting steeper, and I was just trying to crawl it up. I didn't try with any momentum and didn't try gunning it. I'd honestly be shocked to see anything less than a tube framed crawler make it over the top of that ridge. Even if I made it to the top i would have bottomed out trying to get over the ledge.

    I tried crawl mode on the same climb. It got me maybe another 2 feet up but eventually lost traction and started digging a hole. I should add that although both modes eventually had me spinning out in place on probably a 40 degree slope, neither allowed the truck to move backwards or sideways. I always felt in control.

    I tried crawl mode at a couple other spots on the trail that I felt were above my experience level. Crawl mode on a steep hill is incredible going up or down. The braking noises are mildly terrifying coming downhill and it can be jerky and noisy if you tap the brakes yourself or use the mode on fairly level ground. The best crawl moment of the day was a steep hill up followed by an immediate drop off even steeper down the other side. It was like coming over the top of a roller coaster. Nothing but sky into nothing but ground in the windshield. There's a video on youtube somewhere that explains crawl mode as a great tool for people that have no clue what they're doing. Lol I'll agree with that. It got me through some stuff today that I wouldn't have been comfortable with being my first time out. Probably something I won't use often and someone with alot of experience may never need, but nice to have.

    I tried rock mode even though there were no solid rocks around. Maybe it was just the hills I tried it on but absolutely no wheel spin. It felt like I was on tank treads. Great day! Especially for bone stock! The pics dont do it justice
    20160319_163732.jpg FB_IMG_1458439014749.jpg
     
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  8. Mar 19, 2016 at 10:06 PM
    #1308
    David K

    David K [OP] Well-Known Member

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    Thank you! Great reporting.
    So tell me, how to you go from L4 to MTS? Do you push or turn something. Is it like A-TRAC in that L4 is pretty useless on loose surfaces without MTS on? In other words, is L4 normally just open diffs and wheels spinning if you lose traction and MTS must be selected to begin working?
     
  9. Mar 22, 2016 at 12:40 PM
    #1309
    dkg

    dkg New Member

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    This is for 2nd Gen Tacomas.

    Trying to put together a cheat sheet of all the driving modes to stick in the cab of the truck. Trying to understand what some typical uses of the various driving modes might be...can you help me fill in the blanks?

    upload_2016-3-22_12-40-9.jpg
     

    Attached Files:

    Last edited: Mar 22, 2016
  10. Mar 22, 2016 at 2:18 PM
    #1310
    tacogeorge

    tacogeorge Well-Known Member

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    There is a control on the overhead panel. None of it does anything unless you're in 4LO. Then, you just push whichever button you want to activate and use the wheel to select the mode for MTS or the speed for crawl, both of which are displayed on the multi-function display on your gauge cluster.

    [​IMG]

    I didn't drive much with 4LO engaged and nothing else active. I did try one hill with loose rocks going super slow and it slipped, so I threw on MTS and it went away. I guess if you wanted full control in some sloppy mud where your momentum and wheel spin to clear the treads is more important than constant traction and you don't want the computer putting the brakes on. I dunno. I haven't gotten into enough mud to give a good answer.

    @dkg Good idea! Not sure about those other modes though. The 2wd AUTO LSD might help someone without 4wd or with broken 4wd get through some sticky situations. VSC/TRAC OFF I'd imagine is just for doing burnouts and donuts. Don't know.

    I don't have much experience in the ice/snow and zero in this truck but I think I will probably use 4HI default mode the first time I do. I imagine that you want the traction and stability control to keep you moving in the right direction and minimize wheel spin.
     
  11. Mar 22, 2016 at 2:37 PM
    #1311
    dkg

    dkg New Member

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    I cobbled that info together from the beginning of this thread, but am still wondering about when you might want to use some of the various driving modes. I think it mostly pertains to 2nd gen tacomas. Looks like you have 3rd gen if you have crawl control. I'm not sure what driving modes the 3rd gen has.

    Regarding driving in ice/snow. If actually driving on ice or snow, then yes 4H is probably fine. The problem with 4HI on hard surfaces is that the default puts the truck into limited slip. So unless you are going in a perfectly straight line it is not recommended as it adds strain to the axels since the tires want to rotate at the same speed when you go around a corner. I haven't tried it yet, but I imagine turning off VSC which turns off TRAC and gives you an open differential will allow the wheels to spin at different rates while in 4-wheel drive. I'm thinking this is the mode you would want when you are on frozen roads where you might encounter black ice but are generally driving on a hard surface. I have a Jeep that I use for rock crawling and it has a full time 4WD (4HI) option that you can drive on hard surfaces with. I'm thinking 4HI w/ VSC OFF mode would be Toyota's equivalent.
     
  12. Mar 23, 2016 at 6:17 PM
    #1312
    David K

    David K [OP] Well-Known Member

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    Hi DKG!
    That is a cool chart. It applies to 2009-2011 Tacomas (Off Road 4WD).
    In 2012, a 10th drive mode was added. It is in H4, which now normally has TRAC with regulation (as it does in H2).
    A quick press of the button puts you into TRAC OFF (Traction Control with regulation turned OFF... as it is in H2 in AUTO LSD).
    I have a post somewhere for 2012+ modes.

    Now, we need that kind of chart for 2016+. I hope tacogeorge is up to the task!
     
  13. Mar 30, 2016 at 7:55 PM
    #1313
    RiverRat747

    RiverRat747 New Member

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    Hi everyone. Just got a 2016 long bed trd off road. I've been dreaming of getting a taco and finally got one. I tested it out in Moab just a bit to familiarize myself. The MTS was perfect.
    My one question is about the crawl control. It seemed fine in the medium and high modes, but the low mode bucked back and forth like a rodeo. Really unnerving on a ledge area. Is this supposed to buck like that? Is the low crawl only for when you've sunk it to the doors in sand?

    I was also getting the impression from the owners manual that the VSC (trac) should not be on all the time. Is that correct? Does the vsc affect mpg or wear and tear on the diff?

    Thanks everyone. This site and everyone's input is great.
     
  14. Mar 31, 2016 at 6:06 PM
    #1314
    David K

    David K [OP] Well-Known Member

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    Hi, since this is a thread I began I will respond... but suggest you re-ask this in the 3rd Gen Taco forum since I am unfamiliar with the Crawl and MTS other than what I read here.

    Since Crawl is really cruise control for off roading, I would not use it where you need to have full control, like along a cliff. MTS yes, CRAWL no. I think it is the setting for getting out of sand like in the video?

    VSC is Vehicle Stability Control and is a safety system to keep you going in the direction you intend should you begin to go into a spin, like when passing at highway speed on a slick road. VSC is a moving fast system, but it will beep-beep-beep at you off roading in H4 if your truck slides around. This can annoy you, and is often why some choose the VSC OFF MODE. Sadly, that also means TRAC is off with is beneficial at any speed, off road.

    TRAC is the limited slip or Posi-Traction system we have.
    TRY TRAC OFF MODE in H4, a quick push of the button. This is actually TRAC but with the engine regulation turned OFF for stronger limited slip action.

    In H2, this mode is called AUTO LSD and VSC is also OFF to 30 MPH. I am not sure if in H4 that VSC is also off to 30 mph in TRAC OFF?

    I wish someone with a 2012 or newer Taco would confirm. 2009-2011 has only the TRAC OFF mode available in H4, except it was called TRAC with no button touching.

    In L4, there is no VSC... you are going too slow to need it!

    Hope I helped a little!
     
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  15. Apr 8, 2016 at 11:37 AM
    #1315
    bnv

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

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    Just to be clear in the chart above, is it true that number 3, 5 and 6 have no wheel regulation at all. ie any or all wheels can spin, you can do a sand flinging donuts if legal, safe and appropriate?

    Also does number 5 say you can drive on hard drive roads in 4WD-Hi even though Toyota says not good idea?
     
  16. Apr 9, 2016 at 8:24 AM
    #1316
    David K

    David K [OP] Well-Known Member

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    I am not in total agreement with the chart and it has no recommendations for when to use some of the modes... so, I suggest you go to the top of this thread (page 1 and beyond). Nobody should use a $30,000 + vehicle for "donuts"... The truck is amazing fun just driving off road to places others cannot reach... or reach as easily as an A-TRAC equipped Tacoma! As for driving on pavement... of course you don't need 4WD then, but if you want to do the recommended 10 miles a month in 4WD, and you can't get off road or it isn't icy or wet on the pavement (when 4WD is okay), then do so while driving straight only. If you must turn, then rotate the dial to H2 when turning or parking... to avoid binding the driveline.
     
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  17. Apr 9, 2016 at 7:57 PM
    #1317
    bnv

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

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    David K,

    Thanks for the reply and advice above.

    I actually got the "donuts" idea from your first post in this thread Jan 2010:

    "Toyota also allowed us the CHOICE of having LSD or OPEN differentials... Just in case you want the tires to spin freely (rocking back and forth out of a stuck, or doing doughnuts in a wet field)!"

    My intention was to find out what modes had an open differential. Agreed do not want to tear up a near 40k vehicle.
     
  18. Apr 10, 2016 at 12:49 PM
    #1318
    David K

    David K [OP] Well-Known Member

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    LOL... yah, that was 5 years ago when I was younger!

    The Off Road TRD truck always has open differentials except when the rear one is locked. However, the term in this thread applies to when there is no limited slip traction control. In that case, it is when the truck is in the VSC OFF MODE (in H2 and H4) and when it is in L4 (without A-TRAC on and without the locker on).
     
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  19. Jun 22, 2016 at 5:03 AM
    #1319
    DayDay60249

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    For someone that is totally new to truck and all this, this helped a whole lot.. I think in some what understand it all now
     
    Last edited: Jun 24, 2016
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  20. Jun 22, 2016 at 8:42 AM
    #1320
    David K

    David K [OP] Well-Known Member

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    In 2012, a 10th drive mode was added...

    TRAC in H4 was renamed TRAC OFF and requires a quick push of the VSC button to activate (same as AUTO LSD in H2). The OFF part is that engine regulation is off. TRAC OFF is MORE TRAC not less, or none.

    TRAC in H4 from 2012 + now has engine regulation (same as TRAC in H2).

    There is another thread I made with all 10 modes for 2012+ Tacoma OFF ROAD 4x4s.
     
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