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

There is a 4-Lo-Trac Mod for the non-Off Road TRD models... at least for the 2nd Gens.

 

David, yes the 4L lsd mod works on second gen TRD sports. I haven’t done it cause I just don’t want to mess with it. What I really like on my 2009 is when I’m in 4H I automatically have 4wd and limited slip front and rear. It’s amazing traction. I’ve gone places where guys with other trucks and open axles just spun their tires. And thank you David, I learned all this from your excellent posts. You made this shit understandable.

 

You are very kind, sir!

 

My 2015 2g OR has A-trac.

 

A-TRAC was made standard on all Off Road TRD 4x4s in 2009. In 2016, it was modified and made 'adjustable' for different terrain, if you had an automatic transmission... and they renamed it MTS (Multi-Terrain Select) with a 'cruise control' for slow crawling, called CRAWL. The manual transmission 3rd Gens still have the basic A-TRAC.

 

Just want to say that I always sit up straight and smile when I see an update to this post. Nothing recent, but just the same IMO it's on par with the: "4wd System Operation and Help Thread" started a few years ago by poster: DM93 [OP]. Before I came across that thread, the Tacoma 4WD system was just the equivalent of the black box in an aircraft as far as I was concerned. Excellent info and education.

This thread accomplishes the same. I have been asked a few times how the Toyota "Safety Sense" features work and what they do.... My answer was invariably: "Dunno... Nobody knows anything about those systems..." The info in the owner's manual is confusing and seemingly contradictory in some places. Not so once this thread came along. There is a video out there of the system moving a Tacoma sitting on on jack stands with only one wheel on the ground in 4WD-H and 4WD-L and one in real-world conditions on a trail in the same set-up using ruts on the trail.

The system manages to move the truck forward in every case. You can actually see the system search for the wheel with traction in the last test until it was successful.

If there is a "Tacomaworld Hall of Fame" in here somewhere, these two threads should be in it!

https://www.youtube.com/watch?v=BXYFxXUcdYA




Thank you

 

2012 sport 4wd
Explain what i actually have.
Great post!

 

The absolute expert on this is David K who originated this thread. Hopefully he will chime in. It’s my understanding that what you have is 4WD with limited slip in 4H. In 4L you have 4WD open axles with no limited slip.
The limited slip when in 4H increases traction way more than open axles. A Sport does not have an E locker. There is a fix or work around so that you have limited slip in 4L and has been posted here numerous times. If I’m wrong David will clarify.

 

Fantastic response,I assume it’s the yellow wire mod.
I have been reading a lot of post but wanted to verify.
My last rig(20004runner) was a lot simpler.
I would definitely do the mod if it’s worth it without issues.
Thanks

 

Yes. I have a 4wd sport but haven’t done the mod. I actually do a lot of off road for my hunting and fishing trips. No rock crawling but some rough rocky rutted roads and some 4wd trails. So far I’ve gotten along fine using 4H 98% of the time and very little 4L . My only hesitation is that Toyota must have a reason for not having limited slip in 4L but no one knows what that reason is. I assume the mod wouldn’t hurt anything but who knows in the long run.

 

You are so very kind!
Yes, I am still alive and still drive my 2010 Tacoma, although not as often as in the 2010s!
I think my original thinking and discoveries still apply...
Our differentials are OPEN and we simulate LSDs with the BRAKES and spin sensors at each wheel.
2009-2012 +/- are normally in the 'TRAC OFF' or stronger LSD mode anytime we are in H4. The only light is H4. No TRAC OFF light.
A button push option was added around 2012 so that when first in H4 we were in 'TRAC' (lighter LSD) and the quick push of the VSC button would put us into the stronger 'TRAC OFF' mode (as well as a new TRAC OFF light comes on saying so).
In L4, there is no limited slip choices other that ATRAC.
I have been posting a bit in the 60+ forum and still am happy to help with your planning Baja California travels! My book, about the Spanish missions in Baja California, is still in print. I enjoy solving mysteries or making confusion more clear!

 

Thanks David, you are the man.
I have a question for you (probably a dumb question). I have a 2009 TRD Sport 4x4. I understand the brake assisted type of limited slip I have. I assume it only applys to the rear wheels? Or when in 4wd do the front wheels also have the brake assisted lsd? (You explained all this to me somewhere previously in this lengthy thread but this old brain doesn’t retain things like I use to)

 

The Sport and the Off Road (and the SR5, etc.) share the 4WD system and as far as I know, the same spin sensors (for the TRAC and TRAC OFF modes). The MAJOR difference is that ONLY the OFF ROAD TRD has the Hydraulic Brake Booster. It is stronger than the Electronic Brake Booster of the Sport, all to make A-TRAC work. A-TRAC brakes the spinning tires so well that it really mimics a locking differential. The EBB (electronic brake booster) can only slow the spin, so a 'limited' slip vs. a no-slip action.
Your brain is fine or as fine (or fried) as mine!

 

Yellow wire mod
Makes me wonder if Toyota didn’t offer the extra traction in 4low on the sport model so they could claim that’s a plus off the off road?

 

Thanks David. What I really want to know is when in 4H does the front wheels have the same spin sensors/Trac /track off as the rear wheels . Does the ebb slow the front wheels or only the rear wheels.
Thanks my friend

 

On my truck, the traction controls operate on all 4 tires, in H4. Spin sensors are on all 4 tires and work all 4 brakes. I don't think it even matters if in H2 or H4, for safety on wet roads, etc. The benefit with the Off Road TRD is the hydraulic brake booster... which gives a stronger force than the electronic brake booster of all other models. Again, I am no expert nor a tech mechanic. It would be nice to hear from one. See the charts from Toyota I posted on the first page of this huge thread. I wish they made the same charts for the 2012 and newer models.

 

Thanks again David. It all makes sense to me. I’ve noticed when off road with guys with older 4x4’s that have open axles my truck way out performs theirs, much better traction. I noticed recently going up a steep rough rutted road in 4wd I did just fine almost no tire spin. Another guy in an older Chevy in 4wd was spinning tires all the way up. He asked me if I had a locker. I told him no, said it’s all about having a Tacoma. Our versions of “LSD” improve traction tremendously. I’ve also been on muddy roads and other trails where some trucks couldn’t make it like I did. May start calling you Professor David K

 

Too kind... I just like figuring out what's going on then trying to explain it in words we all can understand.
I wrote books on trying to explain irrigation systems, the roads and the missions of Baja California, and monthly articles about travel and history of Baja California. Keeps me occupied, lol! www.vivabaja.com