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

Here is a condensed clean version, in a closed thread (so it would stay clean): http://www.tacomaworld.com/forum/2n...-controls-trac-auto-lsd-trac-rear-locker.html

(link in my sig)


HERE is one that includes the changes made in 2012:

 

Printed , thanks ..

 

Now just have fun, and Let's Go Places!

 

If the road is slippery there is no binding. H4 is aok, just not on hard, dry surfaces when turning.

 

mixed conditions means snow roads for a mile then a mile of dry roads. then 20 feet of compact snow and then 100 feet of dry roads. You can't use a part-time system in these (dangerous) conditions. It's better to use full-time 4wd like the 4runner or AWD system like the Subaru.

I had major binding issues on the ALCAN in my 2007 Tacoma. My truck has no TC or VSC so I'm sure if I had these systems it would have been safer.

 

We had exactly those conditions around here for the past couple of days. I'm new to Tacomas and have had to adjust my habits to suit the vehicle, which basically means switching in/out of 4wd quite a lot in mixed conditions.

 

The VSC does make the truck handle surprise slipping much like 4WD does... as in straightening it out if it begins to slide.

Yes, I am not saying a third differential wouldn't be a cool thing so you could stay in AWD. However, if going from snow to dry pavement frequently, leave it in H4 and only pop it out for sharp turns, parking, etc. The 4WD is for safety, after all. The binding has never been reported as breaking anything I have read, and is only an issue if you are trying to turn your steering wheel and it is too hard with it in 4WD.

 

I hear ya, those conditions are dangerous, in my case I was on the ALCAN which is a windy, curvy, snowy, mountain roads with no guard rails. I was also towing a 5x8 uhaul trailer and when my tires would hit dry pavement in 4H it would bind up and shake the truck and the trailer would start to sway and I had to disengage 4x4 immediately.

My truck would also not easily "pop out" of 4wd. The light would blink for a minute or two sometimes before disengaging. I have read since then that if you put it in neutral and tap the brake it will help to pop out. Perhaps my truck is just old too maybe the actuators are not in the best shape. I had since added winter tires, an alignment, changed diff and t-case fluids, and will give it a go here soon when we get our next snow storm and will report back. My next truck will have TC, VSC, and possibly a center diff! I am sure that if it had vsc it would have straightened me out the time I fishtailed in 2wd going down a steep curvy snowy grade!!

Here is a pic of the ALCAN closer to Alaska. British Columbia had steeper grades and about 4" of compacted snow/ice.

 

The 62mph limit is only for engaging or disengaging 4WD.

Once it is engaged, there is no maximum speed I'm aware of.

 

This is accurate.

I can't think anytime I would 'need' to be in 4WD at freeway speeds, however? Perhaps racing the Baja 500... but if you can drive that fast, you probably don't need the extra traction?

 

Awesome thread…..

 

I thought this was interesting.

http://toyotaia.com/intranet/misc/4wd%20simplified%20one%20page.pdf

 

This is from a Toyota dealer, and not the factory... so there are some questionable lines.

The part that applies to Tacomas:


Part-Time 4WD System
Tacoma, Tundra and FJCruiser automatic

Vehicle is mostly operated in 2WD
mode directing the power to the rear
wheels. When driver manually selects 4WD
mode power is directed to all 4 wheels.

This type of system typically consists
of front and rear differentials with a
center transfer case (no center
differential)

On-the-fly shifting
Toyota's part time 4wd system can be engaged
at the flick of a shifter or turn of a
knob below highway speeds (up to 50mph
on Tacoma, 2006 Tundra and FJCruiser and
up to 62mph on 2007 Tundra. There is no
need to stop the vehicle to engage the 4wd
system.

Benefits
The benefits of a part time system is the
ability to switch from2wd to 4wd.

Tundra, Tacoma and FJCruiser automatic
are extremely versatile because they are
able to use both 2 and 4 wheel drive modes
when needed providing excellent on road in
2wd mode and outstanding off-road capabilities
in 4wd.

Additional Benefits
2wd mode saves fuel and wear and tear on
the drivetrain with 4wd mode providing
additional traction when needed.

Drivetrain Binding on Dry Pavement
The way a part-time 4wd system is designed
both front and rear axles rotate at
the same speed when 4wd mode is engaged.
This splits power at 50% front and
50% rear. On dry pavement this will cause
the drivetrain to bind when vehicle is attempting
any type of turn. Drivetrain binding
causes severe strain on various 4wd
drive components. Therefore 4wd mode on
these vehicles should only be engaged in
slippery conditions such as off road driving
and poor road conditions.

4LO speed
Only to be used in very poor traction conditions
and at very low speeds

 

sud

 

Well, I'm one more person that owes David K a big Thank You for the info in this thread.

I'm just glad to see that I'm not the only one who finds the way Toyota has termed (mainly this) and set up the drivetrain to be confusing. It's awesome but confusing to know what you are or are not doing when you select a givin button.

I'm a big fan of Toyota trucks having had a 88, 95, 01 OR TRD, 05 OR TRD, & now a 14 OR TRD.

I copy and pasted stuff form this thread to create a cheat sheet of sorts to keep folded up in the visor. This just is in a format that makes sense to me. While when I was younger I found my self off road all the time, as I've grown older I seem to do it less and less. So it might be months before I need to use the information I found in this thread again.

Although it has been done and redone in this thread I thought some of you may find this version handy also. This is meant for 2012+ Tacomas.

VSC= above 9 mph prevents skidding while in a turn
TRAC= (Medium) Brake controlled LSD + Engine regulation (H2 & H4)
A-TRAC= (Strong) Brake controlled LSD + Engine regulation (L4 only)
RR Differential Lock= Rear Differential locked (L4 only)
Note: Dash indication lights AUTO LSD in H2 & TRAC OFF in H4 Both mean Limited Slip Differential with no Engine Regulation.

Note: Have transmission in Neutral when turning knob from H2 or H4 to L4.



2012 + (10 Drivetrain Modes)


*Press Nothing...

1) H2= TRAC (Limited Slip with Engine Output Regulation)
2) H4= TRAC (Limited Slip with Engine Output Regulation, front and rear)
3) L4= No Traction Control
---------------------------------------------------------------------------------------
*Quick Press (VSC OFF SWITCH) moving or stopped...

4) H2= AUTO LSD (Limited Slip without Engine Output Regulation, VSC OFF to 30 mph)
5) H4= TRAC OFF (Limited Slip without Engine Output Regulation)
---------------------------------------------------------------------------------------
*Press (VSC OFF SWITCH) and Hold In 3-5 seconds while stopped...

6) H2= VSC OFF (No Traction Control)
7) H4= VSC OFF (No Traction Control)
---------------------------------------------------------------------------------------
*Press A-TRAC switch: (Switch stays in)…

8) L4=Front & Rear (Strong) Near no-slip traction control

*Press of RR Lock Switch (Must have transmission in Neutral)…

9) L4= Locks in Rear Differential (L4 only)

*Press (A-TRAC & RR Switches together)…

10) L4= A-TRAC works the front below 3mph while the rear locker is engaged.

 

Hi Skyboss, I am happy it was helpful. We all read or hear things differently, so I have posted many versions that all still provide the same basics (I hope). Like you, I came from a 2005 before getting the TRAC/ A-TRAC equipped model.

In your reply, I don't get this line: VSC= above 9 mph prevents skidding while in a turn (?)

Don't forget the AUTO LSD/TRAC OFF mode for more TRAC, as well! No engine regulation limited slip.

Have fun with the truck... and get out on the weekends to play with your TOY-OTA!

 

I read that 9mph thing somewhere. Just trying to grasp the difference in VSC, TRAC, A-TRAC. All basic discriptions I find for all 3 say (uses brakes and engine regulation). Only difference I'm getting is that VSC keeps you straight if you start to slid in a turn, & Trac is same a A-TRAC but not as strong/responsive.

I would love to see better discriptions seperating the 3 modes.

Also I diffenately get the AUTO LSD/TRAC OFF(or think I do) (Modes 4&5 on my list). I don't have a lot of appreciation for the engine regulation thing. Maybe I'm missing something.

Thanks again.

 

Think of TRAC as 'Limited Slip'... it will allow the tire to slip some but applies the brakes to slow or restrict the spin, and that transfers power over to the tire with traction. TRAC uses engine output regulation to keep you from over-'reving and making a useless spin, that alone may help you move... then brakes slow any continued spinning. This is the standard mode in H2 and H4.

AUTO LSD/TRAC OFF is stronger limited slip, because there is no engine regulation, only brake action on the spinning tire. Press button briefly to activate. (2009-2011 Tacomas in H4 have this as the standard mode, no button push, and it was called TRAC)

A-TRAC (Active TRACtion Control) is a whole level above TRAC or TRAC OFF. It requires the holding force of a hydraulic brake booster to match tire rotation across the axle, very had to see any difference between a differential locker and A-TRAC when it is active. There is some slip between obstacles, since it is an automatic locking or matching system, and as soon as it detects loss of traction, it goes active to move you ahead. By not staying locked, you can easily steer the truck on tight trails... something lockers don't permit (without turning them off).

 

Thanks again.