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

I hope you enjoy it as much as I... Remember with limited slip systems, even A-TRAC, that if you come to am obstacle that stops your forward movement: to give it the gas and turn your steering wheel from side to side if you wish to dive ahead (and it is safe to do so). It is like 'waking-up' the system when you put your foot into it... similar to loading up the torque converter in an automatic by stepping on the gas and brake simultaneously. The truck will crawl like a tank with all 4 tires powered. It is a beautiful thing!

 

I have a 2WD reg cab taco and want to be sure. Everything you have listed in 2WD is that applicable to 2WD models or is that only for 4WD's in the 2WD mode? Thanks

 

The 2WD modes apply to all. 2013 may have some changes but they seem to be only with the 4WDs.

 

is this normal?


I posted about this before and nobody knew WTF was up, to me it seems that with the 12s there is no option to turn TRAC ON and VSC OFF while in 4H. My v6 was bogging badly while towing a stuck car off a slick muddy road (think hard pack slippery mud where ya dont "dig" ya just fish tail the front and rear and spin on top). I tried hitting the VSC button once and nailed the gas and went no where, it fealt like I had open diffs at that moment. Thats when I didn what I should have done at first and shfted to 4L locked the rear with ATRAC on and gave er hell. Pulled the car like a champ untill the idiot steered himself into some deep ruts, I gave him a LIGHT yank and broke something on his car. I got outta there after that......

So ya, my 2012 does this too. Before all that happened, I thought that I could go from normal 2WD mode to 4H, and have my TRAC WITH OUT the VSC and engine regulation. But I hit the button, it turns TRAC OFF, I HOLD the button it turns TRAC OFF AND VSC OFF.

 

According to your signature/ vehicle info., you have a Sport...?

Let me know if you traded up to an Off Road 4x4 so you can relate to my answers on what my Tacoma does. I will come back and give data, but do let me know which model, and year of your 4x4 Tacoma so I can best help... Thank you!

Let me add that there may have been changes in the 2012 H4 TRAC system I have yet to see a tech sheet/ flow chart on... so until that comes out, just an educated guess that there now is TRAC and AUTO LSD with the same degree of engine regulation as they have in H2. 2009-2011 has TRAC in H4 that is the same as AUTO LSD in H2 (ie. no engine output regulation) in other words TRAC in H4 for us is like AUTO LSD, but on all 4 tires.

The no regulation feature makes the limited slip stronger, allowing the truck to climb out of a stuck if one tire spins. With regulation (TRAC in H2) there is a combination of brake force on the spinning tire and throttle reduction to reduce the chance of spinning. This is fine for street driving in slippery weather, but off road we want POWER!

 

thanx, no I have a sport.I am getting flak over engine regulation in 4h. My truck does not seem to curb the engine rpm in 4h, but I have read threads were others swear their truck bogs down with throttle controls in 4H. If they are turning the steering wheel left and then right, would that kick in the VSC to curb the throttle back? I dont practice the left/ right thing so I don't know. this is the only reason I can think of as to why the engine would be restricted when in 4H and spinning wheels. I thought you want some throttle to get the TRAC (ALSD) to work effectively.

 

here is what is being said about my comment about engine NOT being restricted in 4H


im not even arguing about just ATRAC. the incorrect thing stated by Leggo was that the engine doesn't limit throttle when in 4hi with trac and vsc on. which it does. anyone who has a truck with those features KNOWS it does, get stuck in the snow with everything on and in 4hi, it will NOT let you crank the fucking engine to the redline... I would call that LIMITING the throttle. idc how it does it, and Toyota can state in their manuals that ENGINE output is not regulated all they want, but the fact of the matter is that it DOES. anyone who's been stuck in snow/mud knows it.


I guess I am wondering why my truck still revs up when stuck in 4H

 

I understand your concerns and observations... not in snow, but when climbing steep grades, I have put my pedal down to spin (well to move ahead) and nothing happens, as if the engine is regulated... but, I did not quit.. I mashed the pedal, cranked my tires left and right (to grab fresh terrain), and the truck 'woke up' and pulled me to the top... best way I can describe it... and this was in low range with A-TRAC on (no rear locker engaged). You can see this happening in one You Tube clip taken of me, called One Tri Hill... I get to the steepest point and I stop moving for a few seconds (I am mashing the gas pedal and turning my tires left and right)... then the truck responds and I continue up. However, this is with A-TRAC... which you do not have... so, all I can suggest is to use Low Range (which for you has no traction controls so no regulation... just to spin the tires and turn your tires left and right.

In H4 (High Range, 4WD), to get the tires to spin, turn OFF the TRAC by stopping the truck, press and hold down the VSC SWITCH for a few seconds... lights will come on to tell you VSC (and TRAC) is OFF. They will stay off until you press the button again or turn off and restart the truck, or drive in an unsafe manner at which time the VSC will come back on to keep you from rolling over!

 

Here is the video of the One Tri Hill climb on Oct.9, 2010. At about 30 seconds is where the truck stopped moving briefly before the A-TRAC kicked in.


http://www.youtube.com/watch?feature=player_embedded&v=CG3KhKR0NJk

 

And you still have your same ring and pinion as delivered from the factory, huh?

 

I have never tried a hill climb, but I have tried in the snow (pushing a plow) and I get no regulation like that. Seems counter to what makes the TRAC actually work to me.
So this chart is actually wrong? the part about 4H no regulation, trac on vsc on?

 

Paul: Yes indeed... that was over 2 years ago and not long after our epic Mission Santa Maria Baja adventure! Recently changed both differentials and transfer case fluids to Mobil 1 (75-140 in the rear diff and 75-90 in the other two cases). The rear looked fine, no metal pieces, the other two looked new, specially the transfer case oil... at 40,000 miles.

 

The hill climb was in Low Range with A-TRAC ON... the differentials are open and traction control only begins to brake a tire when the spin rate exceeds the opposite tire spin... to match the rotation speed (as a locker matches the rotation with gears instead of brake pressure).

You are in High Range and do not have the hydraulic brake booster... so braking action is less forceful... and while I don't ever say the chart is wrong, I can only say there isn't supposed to be any regulation in high range 4WD TRAC... any restriction must be coming from braking... if the chart is correct.

If you feel there is restriction, why don't you use low range, or turn TRAC/VSC OFF (as I mentioned before)? If you want some limited slip in low range, then perform the 4-low-trac mod.

 

Thanx david, I don't want to beat a dead horse here. I just want to verify whether or not engine regulation occurs when in 4H, TRAC on,VSC on. I have never experienced regulation but others are saying it does.

 

Let me know as you keep testing! The truck is an amazing off road machine... and while I have had 4x4s before with lockers on the back or center differentials, I have never felt as secure going into the sh*t off road as I have with this truck with A-TRAC.

Just use the heavy pedal anytime the truck stops, but you know it is safe to move on... wake up the A-TRAC (if equipped) or the TRAC, as in your case with a SPORT.... and do the yellow wire (4-low-trac) mod so you can go further in low range!

 

The 'regulation' we feel as VSC corrects spin-outs could very well be braking and perhaps (even though Toyota says no) when the brakes are applied, the engine power is reduced?

I would love to have TRAC in H4 without VSC... for the regulation as well as to kill the beep-beep-beep of the VSC alarm.

In H2, we have TRAC without VSC up to 30 MPH when we engage AUTO LSD (traction control without regulation)... over 30 mph, the VSC comes on automatically.

It would be sweet to figure out how to mod the system to give us 'AUTO LSD' in H4, even if only up to 30 mph! Maybe they did this for the 2012 model...?

 

But a straight push or pull, with wheel spin? Because Toyota defines VSC as corrective action during a turn condition. Could the TRAC be regulating the engine rpm during a straight pull, wheels spinning?

 

so you have open diff's when you hit the dirt? What is trac for then? I am so confused

 

Anyone know who to ask at Toyota WTF is the deal with TRAC and regulation? How can you spin the wheels in 4H if trac is regulating the engine, but you need wheel spin to allow trac to function? how do you get wheel spin with the engine governed down electronically?
I was in a snow bank a few years ago once and I put it in 4H and nailed it. I heard clanking ABS sounds and the truck just went thru like a dozer. I don't remember the engine bogging down or having to switch off the VSC or anything. I do remember being pretty impressed however. A man watching ready to laugh at me, was in shock after I pulled out as well.