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

That is great Paul!

I know that we can read instructions over and over, but when someone else says the same thing IN A DIFFERENT WAY, it sinks in!

Keep on four wheeling!

 

A follow up to the Memorial Day 2010 Mision Santa Maria trip test of A-TRAC:

My third time in with a 4WD Off Road Tacoma.

The previous two Tacomas ('01 and '05) required the REAR DIFFERENTIAL LOCKER to climb the Widowmaker and other grades with little difficulty.

The 2010 had A-TRAC activated when in L4, which was at least for 1/3 of the distance to/ from the mission.

The road was rougher and more difficult than any of the previous trips.

The A-TRAC performed perfectly and I NEVER needed or engaged the REAR DIFF. LOCKER!

Being that the road was worse, plus the 3 foot deep water/ mud bog was no problem either (an open diff. 4Runner required pulling through), I have to conclude that A-TRAC is a superior traction system to lockers (front and rear) in the conditions I have used it on: deep sand, steep climbs, deep water/ mud.

The vehicles on our trip with a front locker had to frequently un-lock it any time a sharp turn was required, which was constant on that road. A-TRAC has no effect on steering abilty.

If you don't have an '09 + Off Road 4WD Tacoma (yet) to experience A-TRAC (Active Traction Control), I just am reporting this so you can look forward to this technology and how well it has worked for me in the deserts of California and Baja California, Mexico. I have been four wheeling since the 1960's and A-TRAC is the most impressive traction system I have ever seen or driven.

See my Memorial Day 2010 trip report in the Off Roading forum.

 

I think it is time to modify my signature, so let me post the last version here (in case a change affects all the previous posts):

2010 TRD OFF-ROAD 4WD with Hydraulic Brake Booster and 9 drive modes:
1) 2WD: VSC and TRAC active, engine regulated ('Limited Slip Lite').
2) 2WD: 'AUTO LSD' ('TRAC OFF MODE'). No engine regulation for 'strong' limited slip.
3) 2WD: 'VSC OFF MODE' (TRAC is off for 'open differential').
4) 4WD-Hi: VSC and TRAC active. No engine regulation for 'strong' limited slip.
5) 4WD-Hi: 'VSC OFF MODE' (TRAC is off for 'open differentials').
6) 4WD-Lo: VSC and TRAC are both off in L4 ('open differentials').
7) 4WD-Lo: 'A-TRAC' on gives a 'locker-like, super strong' limited slip, front and rear.
8) 4WD-Lo: Rear Differential Locked and open front differential (A-TRAC off).
9) 4WD-Lo: RR DIFF LOCK + A-TRAC on, 3 MPH limit.

 

Love the way my prerunner didn't come with any of these...

 

Yah, four wheel drive is not for everyone... You have to want to be able to take your truck beyond the limit, into the unknown, away from the crowds.

 

My second trip onto a Sea of Cortez beach (south of San Felipe) was a bit of a surprise...

Last New Years (2010), was my first time on the beach in my 2010 Tacoma. I was amazed that the new TRAC (automatic limited slip) worked so well, that the normal deflating of my tires to 15 psi was not necessary (for the first time).

I turned off the TRAC and soon got stuck with the differentials in the open (VSC OFF) mode. The fantastic A-TRAC (automatic locking differentials) extracted me from the stuck, without clearing away sand or deflating tires... and I went back into H4 with TRAC back on, and continued driving easily.

Last Saturday (July 3), on a beach about 2 miles from the previous one I was on 7 months earlier, I needed to deflate my tires as the sand was so soft, the TRAC couldn't overcome the bottomless sand/ shell mix. A-TRAC in 4 low also struggled. Once I was aired down, the truck floated as usual...



Art, with his 4WD motorhome with ARB lockers on the front and rear also needed to air way down, as the high tide lapped at his tires!



See my trip report with all the photos, coming soon...

 

LSD= Limited Slip Differential (limits the slipping of the non-traction tire to transfer torque to the traction tire (so you can move). This can be done with clutches inside the differential or the brakes at the wheel... IT DOESN'T MATTER which, because the same effect will happen... and brakes are cheaper to fix than a blown differential.

Some pre-'09 Tacomas (Sport TRDs) had a LSD and no RR Locker.

RR Locker= Rear Differential Locker (locks both rear tires to spin equally no matter if one has less traction than the other)... locked vs. open differential... Helps climbing grades, pulling boats out of the water, getting through poor traction situations.

4WD= Four Wheel Drive (power will go to the front and rear differential equally... The tires with less traction will get the torque and spin (open differentials)... so that means one in front and one in the rear will spin. This is better than just one or two rear tires spinning, usually).

4WD + Rear Locker will give you three wheels with torque... the front wheel getting torque will be the one with the least traction (open differential).

2009+ Tacomas have Traction Control or 'TRAC' in H4 ('AUTO LSD' in H2)... Automaic Limited Slip transfers torque away from wheel with little traction to wheels with more traction, using the brake system and spin sensors. Superior off road driving ability.

2009+ Tacoma Off Road TRD 4WDs have the 'TRAC' and 'AUTO LSD', PLUS they have A-TRAC "Active Traction Control" when in L4 which is best described as 'Automatic Lockers' on the front and rear differentials that nearly 'lock' wheel rotation across the axle for maximum torque to all 4 wheels. Unbelievable traction for a stock truck... They also still have the rear locker, but is is only there for backup. I have gone places with my 2010 that required the rear locker on my 2005 and 2001 Tacomas, and only used the A-TRAC... better than ever!

 

We returned to the same Baja beach 2 weeks later, and once again,the deep sand/crushed shell beach required the tires to be deflated for forward movement to be greater than 'downward' movement.

We had a heavy load in the bed and as we got close to the water on the steep beach, I did try A-TRAC. However, dropping all 4 tires to 15 PSI and getting back into High Range was the trick.

In the following photos you can see the point where I stopped to air down... As the truck 'floated' beyond that place!





Happy Taco on the beach!

 

Hi! We have a 2010 Taco with hill assist etc. The A TRAC light turns on by itself occasionally even without the button being depressed. I'll notice it even going 70 mph on the highway. Dealer says they can't find anything wrong with it though. Has this happened to anyone out there?
Thanks!

 

It will (should only) go on when you go into L4 (Low Range 4WD) if the button has been pushed at least once before in L4... In other words, once activated, you automatically will be in A-TRAC every time you go into Low Range... unless you push the button again.

Now, I know you are not in L4 doing 70 mph, so YOU HAVE a PROBLEM and Toyota MUST fix it... do not allow them to ignore it. Call corporate if you must...

 

Thanks for your input, David K! I will most likely be calling corporate on this one as dealer is not being helpful.

 

Good luck... and may the force be with you!

 

I am buying a new Tacoma soon...Was torn between the Sport and Off road...You have convinced Me,David..
It will be the Off Road.
Thank You.

 

Glad you made that choice... a Sport gives no advantage in driving ability, it is all about looks. The Off Road has enhanced traction with the A-TRAC. I find it amazing that Toyota doesn't do more promoting of it. I didn't know a thing about the new traction controls until after I got my 2010... I was amazed at how improved four wheeling was in a truck that looked identicle to my 2005! With just one front tire having traction, the A-TRAC will pull you out.

 

I'm glad I kept reading. Your write-ups are very thorough. However, I continued to have difficulty until I realized that the A-Trac button could 'only' be used with 4L, AND that in 2WD, you could either press the Trac button once quickly or press-n-hold. Until then, I was having great difficulty in keeping track of A-Trac vs Trac and how one was engage/disengaged vs. the other.

This all makes much more sense to me now and I think I no longer need to memorize the settings, since I can now logic it out. Thanks a ton.

 

With all the work you've done to help explain this, I thought I would do my best to contribute. Though I didn't use the exact same terminology as you (Strong vs. Lite vs. Super Strong etc...), I think the point remains the same. I hope this helps.

 

Great to hear... In the beginning, I thought it was way cool to have so many (9) driving/ traction modes. But, as reality checks in, we only really will use three. 2WD (TRAC on), H4 (TRAC on), L4 (A-TRAC on). Maybe one exception...

Using AUTO LSD in 2WD (quick push of VSC Off switch) is kind of fun on sandy desert roads (posi traction with both tires spinning out dirt in back).

I sure don't see any use for VSC Off mode (opens differentials only by holding the switch in for 3+ seconds while stopped, in H2 or H4)... that was so 2005! Perhaps for those who want to have off road fun in H4 without the VSC warning beeper going off (that is annoying)?

In L4, you want maximum traction... and that IS A-TRAC, so push that button and always be in A-TRAC in Low Range. People pay big bucks for front (and rear) lockers... A-TRAC is that kind of traction, only better!

 

Oh, and by the way. After reading your various posts and accounts of your use and how pleased you are with the Traction Control system, you've convinced me to hold off on doing the Anytime Read Diff lock mod. I'm not sure that it's really necessary. I can at the least hold off for now.

I'm sure my wife would also thank you if she new that your words restrained my hand from cutting more wires on our brand new truck

 

Hey, that is a neat chart... GOOD JOB!

Toyota does call it Active Traction Control... but I like 'Advanced' as well!

A-TRAC is much more than limited slip... it almost locks the two tires across the axle 100%, like a locker... but will allow enough slip for steering control.

 

Fixed