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

Maybe...

But, when I got my 2010 Off Road I didn't know about A-TRAC or the traction controls on it... my 2005 had none other than the rear locker.

I am still amazed that Toyota doesn't hype up the A-TRAC at all... Perhaps those of us with it are doing a good enough job telling others???

The Off Road is the real deal... nothing fake or 'just for looks' on it...
If you need a truck that can go nearly anywhere, then get the Off Road TRD... If you get anything else, it is either for looks or for lower price... or you just didn't know the Off Road had 9 drive modes and can climb like a tractor!

 

Just curious - why would traction control not be superior in snow to non-traction control?

 

When you say "wheeling" I assume you are talking about driving through deep snow for fun. So I can see how wheel speed would clean the tires. If I am driving on fresh or packed snow on the road - I am assuming 4HI with TRAC on would give me better traction than 4HI with TRAC off. Correct?

 

I am no snow driving expert, but I have read of a need to spin tires to try and grab fresh snow to pull ahead. Toyota mentions that as being one purpose of AUTO LSD in 2WD.

Keep in mind, this is only if one tire per axle is spinning (open differential). Traction control does NOT slow down both drive tires... only the non-traction tire to divert torque to the traction tire.

I can tell you in beach sand, where all 4 tires have low traction, the TRAC in H4 is FAR and AWAY better than open differentials...

What happens with open differentials is if you hit a spot with softer sand on one side... then that side tire(s) will begin to spin more and dig you into a stuck (if you let it).

With traction control, that(those) faster spinning tires will be slowed down to keep torque going to the opposite tire(s).

4WD is better than 2WD and limited slip is better than open differentials to keep you moving.

I hope to see some snow driving experts with '09+ Off Road 4WD Tacomas try snow driving in H4 with TRAC (limited slip) and in the VSC OFF mode (open differentials) and tell us how they perform... I will do a test once I get into the snow this winter... I hope!

 

Thanks guys - great info. I gotta say I learned a hell of a lot more from you guys on these threads that reading my owners manual. When it comes to the 4WD system and the TRAC, A-TRAC, etc... the owners manual is useless. It describes 4LO as what you go into when you need "maximum power and traction". Neglects to tell you than TRAC automatically turns off when you switch into 4LO. Douche bags! I gotta say that Toyota going out of their way to purposely disable something that is already built into my truck kind of pisses me off. If A-TRAC is that much better then they should be able to sell it as such - not disable something that would be totally functional and is already there.

 

It was the owner's manual AND saleman's LACK of knowledge about the traction controls that brought me HERE to ask! It was a year ago I got my 3rd Tacoma, and that is when I statrted asking questions on TW... Then I went out and played with my truck to get the first hand knowledge of how it all worked. I still have a few tech questions, but I think I can get by in the meantime!

Why no TRAC in L4 is a great question... and again, maybe it is that way to help Off Road TRD sales, since it has A-TRAC which is even stronger than TRAC... I do think if A-TRAC was promoted better, more would pick that advantage over the 'cool looking' (but non-functional) hood scoop.

There should be some kind of Buyer Beware notice on all Sport TRDs: "Caution: No Traction Control* in Low Range, except Off Road TRDs (*Traction Control is a limited slip system that helps prevent a stuck condition, when off road)"

 

Yeah - I hear ya. Don't get me wrong - I was under no illusion that the TRD Sport was better, or as good as, the OR for off road situations. I drove both - liked the Sport better - mainly for looks - and decided it would suit my needs just fine. I knew the OR had A-TRAC, locker, etc... I decided I didn't need those things. BUT the truck I bought does have TRAC - and for Toyota to purposely make the TRAC not work - when everyhting is there for it to be totally functional is kind of skeevy to me. I guess I can do the yellow wire mod if I decided I needed it. If I ever get into something I can't get out of the way the truck is now (unlikely as I don't go looking to get stuck) maybe I'll do it. I'm driving the truck to St. Louis for Christmas at the relatives. It is supposed to snow - not much maybe 3-5 inches - but my brother andn sister-in-law live at the top of a big hill. If it is snow covered it would be very difficult to get up without 4WD - so we'll see how I do in 4HI with TRAC.

 

Have a nice drive to St. Louis and report back how you did in the snow! H4 + TRAC should be fine! Feliz Navidad!!

 

Snow is inbound here in KC,MO. I promise to test mine to the fullest the first chance I get

I plan to report ASAP.

 

David K was kind enough to point out a misleading part of my Diagram. Previously, I had lumped both the VSC (press) and VSC (hold) as one section (by merging the cells) for the 4H column. However, this may be decieving as simply pressing the VSC button while in 4H will accomplish nothing. You must "Hold" the button for it to have an effect, the effect of open both front and rear differentials.

Below is the updated chart and I've also updated the link in general so that all previous charts are now updated as well, so as to not confuse any that only see the previous chart.

Thanks David for the astute observation.

 

Ok, let's get some conditions in there: The stock OR has horrid approach/departure/breakover angles and ground clearance is too low. The stock tires are not especially impressive for off road traction.

Most glaringly, there's no real armor of any kind on the stock truck.

ORs need plenty of mods to be ready for serious wheeling...I love mine none the less, but let's not pretend they can compete with Rubicons (when the Rubis are running, every now and again...) off the showroom floor.

Is it the most capable offroad pickup stock? With the exception of the limited quantity raptor, probably yes. But the simple fact is consumer vehicles these days that are ready for serious adventures from day 1 don't really exist. They need money dumped into them. The OR Tacoma is an excellent platform to start with.

 

Daved, Thanks for the write up! It was awesome. It realy helped me understand the VSC & TRAC systems. The facted that toyota put the off switch for the VSC is graet. I wonted to up grade to the 2nd. gen tacoma but almost scrapped the idea after hearing guys where having problems with the VSC after lifting there trucks.. But now with the off switch no more problems.. That means Iam back in the game!!!! Thanks again for all the great info. KEEP ON TRUCKEN ON !!

 

Yes, the off switch is there IF you need to spin the low traction tires only, to rock your truck out of a stuck (Toyota says)... instead of limited slip... Special circumstances... VSC works so well on the highway to keep the truck from rolling or doing a 180-360, don't be on the highway without it... IMO... It seems to me, it is always lurking as well, so it might come back on if the sensors feel you are about to wipe out!

Glad you found the post helpful!


HERE is something I posted elsewhere that may be of interest in this thread:

Traction: Better to have it and not need it
... than to need it and not have it!!!

The more traction your truck has the better!

First off, quality tires for YOUR conditions are the first step to gaining traction.

Next, add weight in an empty truck bed to increase traction over the rear drive wheels.

Third, up the level of traction (if you have the equipment to do so).

LEVELS OF TRACTION:

1) 2WD, open differntial. If one rear tire has LESS traction, it will get the torque from the engine... result, spinning tire and then stuck.

2) 2WD, limited slip (differential clutch pack* or TRAC and AUTO LSD). If one rear tire looses traction, the clutches in a limited slip differential or the rear brake on the low traction tire works to transfer torque over to the traction tire. TRAC has engine output regulation, AUTO LSD does not. While the transfer of torque isn't equal between the two rear tires, it does improve the ability to get unstuck. (*'05-'08 Sport TRD)

3) 2WD, rear locking differential*. When activated, torque is divided equally between the two tires. Both rotate at the same rate. Should only be used to get unstuck or cross a difficult surface. Steering ability affected as there is no longer any differntial action (allowing one tire to rotate more than the other, as needed in turns). (*2WD Off Road TRD)

4) 4WD, open differentials. Front and rear drive. The tires with less traction get the torque if traction is less than equal to the opposite tire on each axle. If both tires on the right side of the truck get on ice while the two left tires are on firm ground... the truck stops moving as the two low traction tires spin. Having front drive added to rear drive generally enhances the trucks ability over any 2WD only system. The weight of the engine over drive wheels is one part of the advantage.

5) 4WD, limited slip rear differential. This is one step better as the torque will be shared between both back tires should one lose traction. The torque transfer is not equal but anything is better than one tire spinning per axle.

6) 4WD, locking rear differntial. Both back tires have equal torque along with at least one front tire getting torque. Big improvement in off road ability and a very popular feature used by may companies. All 4WD Off Road TRD Tacomas have this.

7) 4WD, limited slip front and rear differential (TRAC in H4). A big improvement in that torque is shared across both axles. All 2009+ 4WD Tacomas have this.

8) 4WD Active Traction Control (A-TRAC). The ultimate stock traction system equiped on 2009+ 4WD Off Road TRD Tacomas. Provides the traction of front and rear lockers while in low range (L4) by automatically matching a non-traction tire's rotation speed to the opposite traction tire, when there is a difference. Steering control is not affected making A-TRAC superior for trail driving. The rear locking differential is also on the same model trucks should one wish to use it or both together. The A-TRAC will only be active with the rear locked up to 3 mph. A-TRAC used alone has no speed restriction.

9) 4WD with aftermarket front locker (and faxctory stock or aftermarket rear locker). For the true hard-core off roaders as nothing to them can beat front and rear lockers. Both wheels on each axle are gear-locked together for smooth equal torque to each tire. Steering is very difficult, so use of lockers is limited.

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The above is my understanding and experience with 4WD, and I tried to base it on the facts as I know them.

I hope it helps some with understanding how traction systems work, and how well Toyota has done at creating traction vehicles.

Toyota literature does fall short on explaining the traction workings, so I am inspired to write guides here on TW to our truck features, specially when off road!

 

With the bad weather... anyone have some A-TRAC, TRAC, AUTO LSD feedback in the mud or snow?

 

My a-trac slipped


and

I busted my butt

 

A Prerunner with 'a-trac'... incredible!

 

you the only one caught it LOL

 

I have the 2011 TRD but I did not see any A TRACK option? I only have the LSD off option and the Lock Rear Differentail option.

What is th ebest mode to be on the sand? I know on some older SUVs I had to turn off the Automatic Slip Control mode in sand when I aired down. I assume on the new Tacoma all I have to do air it down to about 18 and keep it in 4 HI. If I am in really soft sand or going uphill, or if I start to get stuck, I just Lock the Rear Differential and go to L4 and go Veeeeery Sloooooow so I do not dig in further?

BTW: WHat is your best tire choice for excellent highway driving, snow/rain and sand. That covers 95% of my driving.

 

That is the VSC OFF switch (use it to turn on 'AUTO LSD' in H2 or turn off VSC and TRAC in H2 & H4)

A-TRAC (Active Traction Control) is not an option, but standard on all 4WD Off Road TRD Tacomas from 2009+. The A-TRAC switch is down next to the power outlet/ cig. lighter. Turn it on once when you are in L4, and from then on it will always be on in L4 (as it should be).

Deep sand is my favorite off roading... have a look at some of my posts.

1) If your sand is firm, it may be possible to drive it in H4 (with TRAC on) and not air down... I did in the winter on the beach in Baja... I was amazed, first time I was on that kind of sand and didn't need to air down.
This is the beauty of limited slip 4WD.

2) If the sand is soft and your truck digs in or struggles to move ahead, stop and deflate the tires to ~15 psi... Continue on in H4.

Low Range just wants to dig in... and in sand, you need to float on top... It isn't a horsepower thing like with other kinds of off roading. The Rear Locker only works in Low Range... save it for steep hill climbs or just use the A-TRAC in L4.

Now, in a stuck... (and I turned off the limited slip 'TRAC OFF' and 'VSC OFF' by holding down the switch, while stopped for a few seconds) to see if it was TRAC that had me driving without deflating... and the truck dug in...) I went into L4 with A-TRAC on... gave it the gas... and the truck climbed out of the pit without letting any air out. I went back into H4 (TRAC ON) and continued to drive about.

When I returned in the summer, the heat changed the sand condition and I needed to deflate the tires... SEE the link below "32 PSI to 15 PSI"

As for all around good tire... of the ones I have used on my 3 Tacomas so far, I liked very much both the Toyo Open Country AT and the Cooper Discoverer ATR.

Now, I want a more aggressive looking tire but don't want the noise. I had the Cooper Discoverer STT and won't buy them again because of the noise and they were aweful in the sand (grave diggers). I am liking what I have seen and read on the Hankook DynoPro AT and if money was no object (and they were available) the General Grabber.

Have fun playing with your new truck!

 

Thanks for the writeup, this makes so much more sense now. Have been doing research on this since your post to me over on the "Hard to accelerate with wheel fully turned from park after switching to 4x4" thread. I started reading this and thought this what I have been looking for for an hour and a half and then saw it was your thread, had to laugh. So thanks again and now I am going to go test all this stuff out.