Question regarding 4WD

Is it best to drive in H4 or L4 while it's snowing really hard? Also if I put it in H4 can you use the A-trac or is that only available in L4? Also if it's not avaiable in H4 does the auto LSD still work or not?

Also when switching to H4 or L4 do I go into neutral first?

Thank you very much

 

I use 4 HI in the snow.

 

Can you use Atrac in 4hi?

 

Use 4 hi. You have to put it in neutral or be traveling < 3mph if you want to put it in 4Lo IIRC.

 

Okay thank you, so can you use A trac in 4Hi? If not when can you use it?

 

I searched and found this for you....

http://www.toyotanation.com/forum/showthread.php?t=281880&highlight=a+trac


A-TRAC works in L4 only. Press button, light comes on.

TRAC works in H4 and H2 only... nothing to press, automatic.

Here is the whole enchilada:

After figuring it out... I made some posts over at Tacoma World forums... This should help... The new traction choices are awesome...

I have posted here a lot of details, but I think it will help new Tacoma Off Road 4WD owners (2009+) a lot:
-----------------------------------------------------------------------

Have you wondered about your 2009 or newer Tacoma TRD Off Road 4WD's (USA) with its many drive options or switches/ buttons (VSC Off, A-TRAC) and what they do???

I sure did... and this is my THIRD 4WD Off Road Tacoma (2001 extra cab, 2005 double cab, 2010 double cab)...

The first two had standard 4WD with OPEN differentials (means when you are in stuck or almost in a stuck condition (mud, sand, snow) ONE tire in front and ONE tire in back get power and spins... often helping to bury you deeper! However, the first two also had the LOCKING REAR DIFFERNTIAL... which gave BOTH back tires equal power... This may not help get unstuck unless one of them has traction (on dry or solid ground). Mostly the Rear Locker greatly improved steep hill climbing on rocky roads... in my experience.

Limited Slip Differential (LSD) action means the normal spinning of a tire without traction is controlled or stopped so that the OTHER tire on that axle can get power... This is a great bonus to us off roaders because we need the tires that have traction to work and don't want the other tires (in loose sand/ snow/ mud) to spin and bury us.

LSD (limited slip differential) action can be done inside the differential (with clutches) or at the tires (with brakes). Brakes can be easily replaced as they wear out, but re-building a differential is a bigger issue! Toyota wisely went the brake route for their system.

The system is called 'TRAC' in 2WD* and 4WD High Range. It is called 'A-TRAC' in 4WD Low Range. In 2WD, both brakes and power regulation is utilized. In 4WD, engine output is not regulated.

*Also, in 2WD you can have 'enhanced' LSD with even heavier braking action to the spinning tire with a quick push of the VSC Off switch, which turns on 'AUTO LSD'.
Only in 2WD can you go into AUTO LSD. Since we have 4WD, I would think using it would be even better than AUTO LSD? Perhaps helpful for those with only 2WD.

Toyota also allowed us the CHOICE of having LSD or OPEN differentials... Just in case you want the tires to spin freely (rocking back and forth out of a stuck, or doing doughnuts in a wet field)!

To have open differential(s):

2WD: Normal is TRAC on... Hold the VSC Off switch (the one with the truck and wavey tire lines) down for 3+ seconds, while stopped. VSC, TRAC and AUTO LSD are all off.

H4 (4WD High Range): Normal mode is TRAC on... just like in 2WD. To open the differentials: Hold the VSC Off switch down while stopped for 3+ seconds and TRAC and VSC are turned off.

L4 (4WD Low Range): Normal mode is open differntials.*

*Many of us find it odd that L4 is normally in the open diff. mode... as you would typically only use L4 for the most severe traction situations where LSD would be a benefit.

To activate LSD in L4, push the A-TRAC switch next to the cigerette lighter. Once pushed, A-TRAC will always be on in L4, unless the switch is pushed again.

The Rear Differential Lock is also available in L4 with or without A-TRAC (LSD on the front axle) turned on. With A-TRAC on, one would have maximum traction, however when the rear is locked, A-TRAC only works when the truck is going less than 3 mph. Obviously, Toyota wants us only to use the rear locker for getting unstuck or very slow crawling. VSC, TRAC and ABS are all off in L4, as well.

For typical driving, H2 (TRAC on) and H4 (TRAC on) will do almost everything you would want. In L4, I think you would do better with A-TRAC on... would give you the same traction benefit as when in H4... So, that would be the only switch to activate when four wheeling slow in low range... unless you did get stuck (if that was possible now). In that case, you have the Rear Diff. Locker to activate in L4.

I had the opportunity to test the new truck in deep sand and hill climbs shortly after getting it and was amazed at the improvement over the previous Tacomas' open differentials. The truck in H4 would not get stuck in sand with the tires fully inflated. In the past, lowering pressure to 10-15 psi would have been required. After driving around in H4 (TRAC on), I opened the differentials (TRAC off) and the truck bogged down in the sand (got stuck). I then went into L4, A-TRAC and Locked the Rear Diff. I applied the gas and the truck pulled itself out of the sand! All without getting out of the cab to remove sand from in front of the tires or letting any air out. Once 'on top' of the sand, I switched back into H4 (TRAC on) and drove about easily.

In a nutshell:

2010 TRD OFF-ROAD 4WD DC with 9 drive modes (using VSC Off, A-TRAC & RR Diff Lock switches):

1) 2WD: VSC and TRAC active, 'Vehicle Stability Contro'l and 'Traction Control' (Limited Slip Diff.).
2) 2WD: Switch turns off 'TRAC' and 'VSC', and turns on 'AUTO LSD'. Gives maximum power to tire with traction by braking spinning tire, without cutting power.
3) 2WD: 3 second push of switch turns off VSC, TRAC & AUTO LSD for open differential.

4) 4WD-Hi: VSC and TRAC are both on. No engine power is cut in TRAC while in H4.
5) 4WD-Hi: 3 second push of switch turns off VSC and TRAC.

6) 4WD-Lo: VSC and TRAC are off (open differentials).
7) 4WD-Lo: Push of A-TRAC button activates A-TRAC (Locker-like limited slip).
8) 4WD-Lo: Push of RR DIFF LOCK switch to lock rear differential.
9) 4WD-Lo: RR DIFF LOCK and A-TRAC combined. 3 MPH limit.

================================================== ========

This from: http://www.sae.org/technical/papers/2000-01-1636

Active-TRAC (A-TRAC) is the system for off-road 4WD vehicles. This system consists of independent four wheel brake control system and engine torque control system.

This system applies the brake to any spinning wheel, and sends torque to the other wheels with grip. Therefore, the vehicle gets strong LSD(Limited Slip Differential) effect, and it has the same traction performance as a center and rear differential locked vehicle.

Because the vehicle with A- TRAC does not have a differential locking mechanism, it no longer has the phenomenon of tight corner braking, and it frees a driver from operating the differential locking system. Therefore anyone can easily enjoy off-road driving with A-TRAC.


Another... from: http://behindthewheelnews.toyota.com/


Over the past several years, driver assistance features have become commonplace. The functionality and convenience of these systems continue to help develop vehicle collision avoidance capabilities. By their very nature, driver assistance systems are designed to help detect, judge and react to anticipated collision scenarios.
Anti-lock braking system (ABS) is probably the best known driver assistance feature. ABS has evolved from simple lockup control only during braking to more advanced systems that control traction during acceleration, braking and cornering by braking wheels individually while integrating other vehicle operating factors such as engine power output.
Most new vehicles are equipped with ABS these days, but ABS is not a one-size-fits-all system. ABS can include a number of additional features, which are found on a number of Toyota vehicles:
Electronic Brake-force Distribution (EBD) -- modifies braking force at individual wheels to compensate both for changes in vehicle load (occupants and cargo) and to help increase braking efficiency during cornering.
Brake Assist (BA)1 -- monitors the force with which the driver depresses the brake pedal and provides additional brake fluid pressure when the system detects an emergency stop.
Traction Control (TRAC) -- helps reduce drive wheel spin during acceleration using ABS and control of engine power output.
Vehicle Stability Control (VSC)2 -- helps prevent skidding or spinning while cornering by controlling ABS and engine power output to help keep the vehicle traveling in the steered direction, even if the driver enters a turn too fast or steers the vehicle too sharply for road conditions.
Vehicle Dynamics Integration Management (VDIM)2 -- combines a range of vehicle stability control functions into a single, seamless process to help provide overall vehicle dynamic drivability.
SUVs and trucks, such as the Toyota Tundra and 4Runner, may be equipped with specialized ABS-based functions such as:
Active TRAC (A-TRAC) -- During 4-wheel-drive operation on a snow-covered road or in rugged off-road conditions, A-TRAC controls engine output and brake fluid pressure so that the drive force is distributed to the wheels that have traction. This enhances drivability in extreme road conditions, an effect that is similar to a Limited Slip Differential (LSD). Off-road drivability is equivalent to having the center differential locked and a Limited Slip Differential on both front and rear axles.
Auto Limited Slip Differential (Auto LSD) -- Auto LSD uses the TRAC system to achieve the capability of a Limited Slip Differential (LSD) when driving in 2WD mode. (On a 4WD vehicle, Auto LSD only operates when the vehicle is being driven in 2WD mode.) Because Auto LSD and Rear Differential Lock perform similar functions, vehicles may have one system or the other, but not both. While Auto LSD components are similar to those in the TRAC system, there are important differences.
Downhill Assist Control (DAC)3 -- DAC allows the vehicle to descend a steep hill in a stable manner without the wheels locking. It does this by controlling hydraulic brake pressure at all four wheels, helping to maintain a constant, low vehicle speed.
Hill-start Assist Control (HAC)3 -- The basic function of the HAC system is to help increase control on steep upgrades and stopping and starting on slippery surfaces. The HAC system is designed to help prevent the vehicle from rolling backward or slipping sideways during transition from a stopped position to climbing an upgrade.
================================================== ========

I am happy to put stuff down in a way we can understand... Here is another way that may help to see the nine modes as being different:

Basically, we have:
1) 2WD with 'mild' LSD (Limited Slip Differntial called 'TRAC'),
2) 2WD with 'strong' LSD called "AUTO LSD", in the TRAC Off mode), and
3) 2WD with open differentials (VSC Off mode, for both TRAC and VSC off).

We have:
4) H4 with 'medium' LSD (TRAC with no engine output regulation), and
5) H4 with open differentials (VSC Off mode)

We have:
6) L4 with open differentials,
7) L4 with 'strong' LSD (A-TRAC)
8) L4 with rear locker and open front differential, and
9) L4 with rear locker and strong front LSD (A-TRAC).

As for when you use those 9 modes... well, whenever you need to! Seriously, the standard setting in H2 and H4 will work. I have never needed AUTO LSD because I have 4WD, so why put your truck through any stress?

H4 with TRAC is fantastic for most 4WD applications... I was amazed on how it took me over deep beach and arroyo sand without deflating the tires (as always necessary before).

L4... well this is the one mode that I say to push a button for, the A-TRAC button, and leave it that way. L4 is for slow crawling up and down grades or through deep snow/ mud... or if you do get stuck in sand. Amazing technology makes our Tacomas tractors (almost)!

Locking rear differential: Well, with A-TRAC I just don't know if this is important anymore. Better to have it and not need it, then to need it and not have it! Before A-TRAC, I used the locker many times for steep hill climbing... and it worked. Try a steep climb and if you are halted before you get to the top... try the locker and see if you get any further. My testing at Ocotillo Wells, didn't do anything more than wher A-TRAC got me... There is more 'testing' to do, however!

OPEN DIFFERENTALS? We have the option of making the differntial(s) open in all three drives (H2, H4, L4)... if you just gotta play in the snow or mud with one tire per drive axle spinning away, and the other doing nothing... like on the pre-2009 Tacomas.

So, you have traction opens galore! However, the standard mode in H2 and H4 will take care of you... and push the A-TRAC button once in L4 and leave it that way... making it the 'normal' mode in L4, will be the way to go IMO!

Have Fun Everyone!

 

4L under 5mph

 

All that on A-TRAC and the other drive modes was posted here on TW first by me... There were 'lost souls' on that other forum, so I shared there, too... See link below in my sig.

To answer your basic questions:

Use H4 (which has TRAC without regulation) when you no longer are on dry pavement if you feel a loss of traction. (AUTO LSD is for 2WD only and is basically the same TRAC without engine output regulation)

Use L4 with A-TRAC, if condition cause you to come to a stop and must go through very heavy/deep mud or snow, or steep terrain. Sand is better crossed in H4 with tire pressure dropped to 10-15 psi if TRAC alone doesn't stay on top.