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

Well, A-TRAC (only on the Off Road TRD 4x4) is what is the big deal... NO SPIN but works all 4 tires that have traction with more brake pressure on a spinning wheel than TRAC can provide... Possible because of the hydraulic Brake Booster that only that model Tacoma has. All others have the vacuum brake booster which cannot halt a non-traction tire, but does slow it down so more power can go to the traction tires.

 

Not too sure about that part; don't get me wrong I love my Atrac but sometimes spinning both rear wheels helps. I.e., clearing all the crud that builds up in the treads. The Atrac does an EXCELLENT job at not digging in but at some point you got to spin the tires to clear them and keep moving forward.

Just my $.02, take it for what it's worth.

 

VERY interesting. I'll have to check this out when i get in the truck during lunch.

 

Lots of great info ... too bad my 3rd gen doesnt have ATrac - its the 6A transmission so it has the crawl and mts system instead. Now thats a lot more settings to figure out!

 

Made it super simple. Buying an ARB locker. On/Off. Simple

 

So, I like to think of myself as fairly intelligent, but maybe I am giving myself too much credit. There are a lot of options here and while I can read what has been written I am having a more difficult time translating what is written into real world use. My previous truck was a Mazda B4000 4X4 that has now been relegated to a dedicated plow truck. That truck has two choices in 4WD, high and low. Driving the Tacoma I do not use for rock crawling or serious off road fun. Living in Maine we do get snow so H4 is typically all I use unless I am helping pull someone out of the ditch or snowbank. This past Saturday I drove it to my parents house and promptly put the truck just in the snow bank just slightly along the edge of the driveway, with the passenger side edging towards the ditch. H4 would not allow me to move forward and I was concerned moving backwards might cause me to slide off the side of the driveway. I tried to put it in L4 but believe I was not engaging L4 correctly as I did not shift into neutral when I flipped the switch. The indicator light was blinking and the truck was beeping when it was in L4. Am I correct in thinking that I never put actually put it into L4 and that is what the blinking icon and beeping was telling me? Reading this thread as a means of doing my homework I am fairly certain I did not put the transmission in neutral to switch into L4 so it probably never did. I ended up "rocking" the truck by hitting the gas then lifting off the accelerator and repeating with the wheels pointing just slightly to the left, causing the truck to walk sideways a bit to the point I could back up safely without sliding over the edge of the driveway. Then I just drove out with not problems. Compounding my problems are that the stock tires have about 30K on them and the Toyota dealership insisted they have lots of tread left but I think the tech is on crack. I am picking up some Hankook Ipike W11 tires tonight to run during the winter.

In real world conditions I understand that for the vast majority of the time normal H4 will suffice for on road winter driving conditions.

Would I want to use normal L4 for situations like deeper snow or like when I was stuck on the edge of the driveway as I described above? How about if I was trying to pull someone else out who was stuck? Normal L4 or would it make more sense to select one of the other 8 different modes that we have to choose from.

Any and all insight is appreciated.

 

L4 should be tested before you need it... forgetting to put the tranny in neutral on automatics (or fully depressing the clutch on manual trannys) is common... The beeping is supposed to remind you! However, if you never have used it before and don't read any of the instructions in the manual (or on your sun visor card), then you have no clue, do you?

You use L4 when you need maximum power for climbing, pulling, crawling... not for speed.
Your road ahead is deeply rutted, full of rocks, deep in snow or mud: L4
If equipped, always engage the A-TRAC when in L4. A-TRAC (or MTS on automatics since 2016) makes sure power goes to the tires with traction rather than spinning non-traction tires the way open differentials normally do.

 

You do have the A-TRAC system. It is in the MTS, so think of it as an adjustable A-TRAC based on the soil conditions below your truck. Just dial to the type of ground conditions you are on... simple!

 

Thank you! Im heading out for snow wheeling tomorrow so ill put it to use.

 

Great... For fun and research, try all the various traction choices and report back your findings.
Here are (some of?) your traction options in 4WD:
H4 TRAC ON (normal mode)
H4 TRAC OFF (quick push of button, moving or stopped)
H4 VSC OFF (stop, press and hold in until light comes on)
L4 (normal mode)
L4 Rear Locker On
L4 MTS 'SNOW'
L4 MTS + Rear Locker

You also have CRAWL to play with!!!

 

Thanks for the info. And I expected to be chastised a bit. Deserved and I was opening myself up to it on purpose. When I purchased the truck I did read the manual and did understand what I needed to do. It has just been awhile since I had a need to operate in L4. I realized I could find out the information about the beeping by reading but the second part of your answer was more what I was looking for. I had actually forgotten about that sun visor card! Just confirmation that what I thought I understood I truly did understand.

 

I just bought a 2017 TRDOR 4x4 manual. I am trying to understand when exactly to use ATRAC and when to use the Rear Locker. Is there a time when I should use one instead of the other? Should I always use both? If so, why are there two seperate buttons? Looks like Toyota would have both come on by the press of one button instead of multiple buttons.

Yes, I am confused. Owners manual not completely clear....

 

1) A-TRAC always when in L4. There is no benefit to two tires spinning when you are trying to move.
2) Rear Locker is for emergency only (just as the sticker on your door says)... IF A-TRAC doesn't get you through (and I have yet to have that happen). A-TRAC is = the traction of having lockers on the front and rear but without the steering problems that lockers have.

The ONLY time to not have A-TRAC on is if you want the tires to spin freely. Per the manual to clean out mud/snow from your tires... I say get BETTER tires!

I have had the locker on with A-TRAC when pulling stuck Tacomas (non-A-TRAC model) up grades... The reason is with the locker on, A-TRAC only is active under 3 mph and there is no engine regulation, so momentum can be maintained in an emergency pull.

SEE:
http://www.youtube.com/watch?v=9m1u1pba4Ps

 

Results of testing modes in a foot-plus of snow. It was a balmy 8 out, so heated seats got a workout, too.

H4 TRAC ON (normal mode) - works fine, but on uphill or moguls it engaged and it made getting through a challenge.
H4 TRAC OFF (quick push of button, moving or stopped) - worked better than on, vsc prevented tail from kicking out allowing better control.
H4 VSC OFF (stop, press and hold in until light comes on) - let tail kick out, which is sometimes fun, making control harder on cambered terrain.
L4 (normal mode) - worked perfectly, good throttle response, no issues
L4 Rear Locker On - didnt try
L4 MTS 'SNOW' - mud setting worked really well, definately the best setup for hills rutted with moguls covered in snow. I had a lot of three wheel (and the occassional two wheel as it tipped balance) and it never felt unsure of keeping the line. Never got stuck, never bogged down.
L4 MTS + Rear Locker - never explicitly engaged locker as MTS mud mode did everything needed.
Crawl felt too slow for snow, like it was rerpeatedly getting stuck then clawing free. Not a good fit for deep snow. Maybe if it actually got stuck it would be good for getting out.

Overall, when in any 4L setup it performed so well that it was no challenge at all. Definately a beast.

 

Awesome... Thank you!
TRAC OFF in H4 is poorly named, because TRAC is not turned off... It is actually the higher level of TRAC because the engine output regulation is what is turned off. Maximum power and full limited slip action is what you have in TRAC OFF MODE.
Your research proves that TRAC OFF is the premier mode in High Range.

If the locker wasn't used because it is difficult to engage, try stopping, press the RR Locker button, turn the steering wheel all the way to one side (left or right), and then slowly move ahead.

With A-TRAC (MTS), the locker may never be needed, but it is fun to compare how it works or feels.

GOOD JOB!

 

@David K - this is a phenomenal write up. I have a 2012 TRD Off Road and have hardly ever used the 4x4. I too was confused by all of the options and drive modes. The mot necessity i have for 4x4 here in MA is snow and ice. Would you think that the most common mode i would need to use would be 4H with Trac and VSC engaged? If this is the case is it as simple as placing the truck in neutral and engaging the 4H option or are there any buttons that require application as well? I'm used to manual 4x4 systems so the operators drive control assist options are new to me and confusing. I placed my truck in 4x4 H the other day while on a mild grade covered in ice and it didnt go anywhere the trace light just blinked repeatedly and the tires spun, it didnt seem to be in 4x4 at all. Perhaps it ws just too icy?

Thanks for any help and guidance.

 

You can go into 4h while you are moving, don't have to be in neutral. I usually just let off the gas, turn the knob, then lightly get back on the gas.

 

Happy New Year!
drwx is correct, H4 is shift on-the-fly!

I would do the quick press of the VSC button for TRAC OFF (more traction control and the engine regulation is what is turned OFF), if you have any problem moving. 2012 was the first year that the button needed a press, 2009-2011 is normally in TRAC OFF in H4. However, in those years, it was simply called TRAC in H4 and no TRAC OFF light comes on.

IF you need your tires to spin without any limited slip control (to clear out snow or mud from the tires or to just not have any control on the tires spinning, then STOP moving and press and hold in the VSC button. In a few second the VSC OFF light will come on.

Anytime you press the VSC button again OR restart your truck, the automatic setting of TRAC ON is where you will be back to. Simply quick press (moving or stopped) for more traction control or hold in the button (stopped) for no traction control.

 

Thanks All,
Big storm here today so i had the chance to play around with some of the drive modes. 4h with normal mode was pretty decent, 4h with trac off - and 4h with trac and vsc off were all pretty similar, i got slowed down on an icy driveway, i placed the truck in N shifted to 4L and used ATrac for the first time - wow i didn't even touch the gas pedal, i simply let off the brake pedal and the truck pulled itself right up the hill - i was definitely impressed.

 

I cant believe there is no atrac hack or LSD in L4 for the newer Tacomas without a locking rear. atrac I can understand since its not equipped but why wouldnt LSD be able to work in 4L? I found this frustrating my last trip out, where I was getting tire spin climbing a steep slippery/rocky hill.