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Toyota 4WD systems explained

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Comments

  • fox6fox6 Member Posts: 3
    Is there anyway possible to tow an 04 Tacoma 4x4 with 4 wheels down. Have had several conflicting answers. foxo6
  • fox6fox6 Member Posts: 3
    I have anautomatic transmission Tacoma. Is there anyway possible to tow it behind motorhome with all 4 wheels down?I have been told I can put transfer case in neutral & transmission in park & stop every 2oo miles & run through the gears& this would work.Also been told will not work.Please help.Thanks fox06
  • cc124cc124 Member Posts: 1
    I am considering purchasing a RAV4 4WD and was wondering whether or not the 4WD feature will be enough to allow it to be drive in the sand/over sand dunes, such as ones in Carova Outerbanks North Carolina...If yes why? If no, why not? Thanks for your feedback.
  • ustazzafustazzaf Member Posts: 311
    I am a trailer man, so you can ignore me if you want, but throwing the truck on a trailer of a similar length will not add a whole lot of length while keeping miles off the truck and alot of piece of mind. If you put 20K on a $1200 trailer, you still have a $800 trailer that you need to spend $20 packing the wheel bearings. If you put 20K on the truck, you have to pay a whole lot more to pack the 4wd bearings, drop atleast a grand in value and you have to worry about something going wrong with something on the truck while towing, costing well over the $1200 you have invested in the trailer. An example is a wheel bearing going south. Worst case on a trailer is a new axle, hub and tire at around $300. The Toyota hub, tire and labor is going to see the better side of $1200, and that is the low side. Add a few grand and you can have an enclosed trailer that will protect the paint, windshield, and give you more secure storage.
    Just my 2 cents.
  • ccarofknowldgeccarofknowldge Member Posts: 19
    I have read the "Toyota 4WD Systems explained" thread in the Toyota 4Runner forum, but I am still a little confused about the differentials in the 4Runner and the RAV4.

    Here are my 4Runner questions...

    Does the 2006 / 2007 V8 4Runner have a Torsen rear differential, or a Viscous Coupling Limited Slip unit in the rear differential, or does the rear differential simply rely on the Traction Control system to accomplish slippery surface wheelspin control on the rear axle ???

    When the 2006 / 2007 V8 4Runner Torsen center differential is locked by the dashboard switch, is the Traction Control system disabled ???

    Does the Traction Control system wear out the brake pads / warp rotors at lower mileage than a vehicle without traction control ???

    How capable is the 2006 / 2007 4Runner V8 on ice and in snow ??? I have family members that often need emergent medical care. I have to be able to get to care providers regardless of weather.

    There was something mentioned about wanting to disable the traction control for situations like pulling onto a highway in the rain to avoid having it slow you down suddenly and put you at risk of getting rear-ended. Is this accomplished by a switch or pulling a fuse or some other modification ???

    Thanks in advance for any info.
  • 2toyotas2toyotas Member Posts: 104
    The rear has an open differential, which relies on traction control to limit wheel spin.

    When the center differential is locked the traction control system is still active.

    No. When a wheel is slipping, it doesn't take much force to brake it. My brother is pretty hard on is 04 4Runner,with 30,000 miles brakes have 75% pad left.

    Very capable. If you get really bad winters, put snow tires on in the winter and it will be unstoppable.

    I think this mainly happens on the V6 when in 2WD. It is very hard to slip a wheel in 4WD.
  • ccarofknowldgeccarofknowldge Member Posts: 19
    Thank you for your very detailed reply. It is very much appreciated.

    Another 3 questions, if you can answer:

    When the 4 Lo Range is activated does that automatically lock the center differential ???

    Does the Traction Control function on the front wheels also ???

    Does the Sport Model suspension hop around when driven on less than smooth highways ???

    Thanks again.
  • nedzelnedzel Member Posts: 787
    Note that locking the center diff turns off spin control. As previously noted, it does not turn off traction control. On road, even in moderate snow, there's no need to lock the center diff. Lock the center diff in extreme conditions. I doubt you will ever find such conditions on the road.

    It performs well in snow, but realize that the controlling factor in snow is your tires. The 4WD system will allow you to accelerate quite well in snow. But it doesn't improve braking and turning performance. The OEM Dunlops absolutely sucked in the snow -- acceleration was fine but braking and turning were completely horrible. I purchased a set of dedicated snow tires. I've driven through 1 1/2 feet of snow without a problem.

    Traction control functions on the front wheels as well.

    Concerning the ride quality, I strongly suggest that you take one on an extended test drive. The 4Runner is a truck. It drives pretty well, for a truck. It handles pretty well, for a truck. It rides pretty well, for a truck. But there is no mistaking it for anything other than a body-on-frame truck with a live rear axle. My 2003 4Runner does have a mild hobby-horsing motion on rough pavement. You can certainly feel that heavy rear axle moving around. It is not a sedan, minivan, or car-based SUV. It's big and heavy with a high center of gravity. It's cornering limits are low and when you reach them it will understeer mightily.

    I've never had a problem with the spin control kicking in prematurely on rain-slick pavement. The 4WD system provides plenty of traction in such situations. I do feel the spin control is a bit over-eager in snow. In those situations, the spin control can cut in a bit too quickly, shutting down the throttle. You can turn lock the center diff (thus defeating the spin control) in the snow, but then the truck gets a bit tail happy. These days, I only lock the center diff when I'm offroad. The true answer to this issue is to get snow tires. Once you do that, you'll have all the traction you'll ever need in the snow.
  • ccarofknowldgeccarofknowldge Member Posts: 19
    I am confused again. If traction control and spin control are different, what does each one do?

    I was not asking about the ability to prevent vehicle understeer, oversteer, and turnover. Instead I was asking about the ability to send power to wheels that have grip to pavement or tractionable snow or tractionable ice.

    Once I can get going, I usually can drive cautionsly enough with a good set of tires to stay in reasonable control. If I cannot get going at all I'm in big trouble.

    I know the importance of good tires. I do appreciate very much what you folks are saying about this. I have had some really bad all season tires that I threw away practically new at great replacement cost, but I felt my life and the lives of my passengers, (and everyones property too) was worth it.

    I have had to use center differential lock and lo range on some of my older full-time 4wd suv's to get off of ice. That's why I'd like to know if 4 Lo automatically locks the center diff and if locking the center diff disables the limited slip system on the rear (whatever it's called), and if the limited slip effect works on the front diff / wheels too.

    I've used limited slip clutch pack rear diffs and they stink on ice and snow. Vehicle fishtails dangerously.

    I've used viscous limited slip on rears and centers operating in conjunction with standard open diffs and they worked great for me. Always got me going and no fishtailing.

    I've used computerized electromechanical center diff systems in the center and they worked well, though not as well as viscous limited slip on top of standard diff.

    I've never used torsen diffs at all, but they have a good rep.

    I've never had computerized brake control limited slip (whatever Toyota calls it). I came here to get info.

    I appreciate all the help you folks are giving me.

    Looking to buy a new 4Runner V8 Sport Edition.

    Have driven truck / suv's before. Know they ride hard. Just wondering what degree of punishment Sport Edition will doll out. :-)

    Thanks again.
  • 2toyotas2toyotas Member Posts: 104
    I think when Nedzel says spin control he means VSC Vehicle Stability Control,which corrects oversteer and understeer around turns primarily. When you lock the Center Differential VSC turns off. Traction Control never turns off, and it works on all 4 wheels independently all the time. When the center diff is unlocked the torsen splits power front to back,normally 40% front and 60% rear. It can send up to 71% to the rear, and 53% to the front. Traction control send power side to side on the front and rear axle by braking the slipping wheel. When you lock the center diff both axles get 50% and traction control still does its job.

    When in low range the torsen still works, or you can manually lock the center diff. Traction control does the same thing in low range.

    The Sport uses XREAS suspension which I have on my Limited as an option. It links the front right shock to the left rear, and the left front shock to the right rear. It works great, and in my opinion makes the 4Runner one of the smoothest body on frame SUVs on the road.

    As for traction on ice and snow, it will plow through anything, and start on ice with no problem. If you drive cautiously you will be fine stopping, but it will slip on hard stops. Snow tires change that, I put Blizzaks on my 4Runner, and the slipping stopped. It will stop on a dime on snow and ice. An All Terrain tire like Bridgestone AT Revo will do a pretty good job too.

    In my opinion you will not be dissapointed with this truck!!
  • ccarofknowldgeccarofknowldge Member Posts: 19
    Thank you very much. Now I understand clearly.

    Is there any kickback in the steering wheel when the brakes clamp down on a tractionless spinning tire on the front axle ???

    "No kickback" in steering was supposed to be one of the advantages of using either a viscous limited slip with standard differential on the front axle of 4wd's or a torsen type differential on the front axle of 4wd's. Clutch pack diffs tried on the front axles supposedly snapped the steering wheel hard when they locked for those who dared to try it.

    How does the Toyota traction control system behave as felt through the steering wheel when a front wheel gets locked down ???

    Thanks again.
  • wwestwwest Member Posts: 10,706
    The Toyota traction control system, as with most others, always brakes both front wheels even though only one may be slipping. And keep in mind that this isn't "full" braking ability by any means, moderate, on and off braking much like ABS "feel" and sound but with reverse duty cycle, more off that on.
  • 2toyotas2toyotas Member Posts: 104
    Wwest you are dead wrong. The Toyota system has a 4 Channel ABS system, it brakes all 4 wheels independently. If one front wheel is slipping it brakes just that wheel, and the open differential sends power to the other wheel. Where do you get your information?
  • wwestwwest Member Posts: 10,706
    Having 4 channel ABS capability doesn't mean the traction control firmware is (or should be) set up to bust knuckles or yank the stearing wheel from an unexpecting, inexperienced, driver's (John Q. Public) hands.

    Besides which doesn't the 4runner allocate engine torque 30/70 F/R in AWD (non-locked center diff'l) mode? That would make it unusual, rare, for a front wheel to break traction first.
  • friendly_jacekfriendly_jacek Member Posts: 96
    I have V6 4WD but was not brave enough to try. Still wondering myself.
  • chiefjojochiefjojo Member Posts: 39
    I have a 2002 4R. When I lock the center diff in 4WD, VSC (yaw control) is off--no argument there. There is some confusion about whether the TRAC function stays on or not. Toyota has used versions of this system since (I think) 1999 or at least 2001 with the 4Runner. With the new FJ, Toyota has clearly spelled out that there are two versions of the same traction system, TRAC and ATRAC. I believe this is a newer version (3rd generation system?)of the same system Toyota has been using for a number of years now, including the 4R and Sequoia.

    TRAC (traction control) works in 2WD-Hi or 4WD-Hi with open center diff (essentially AWD or full-time 4WD-Hi mode where you can drive an any surface). ATRAC works in 4WD-Hi or 4WD-Low with center diff locked (off-road mode if you will). I believe there is some difference in how it works based on whether you are on or off-road. In my experience, TRAC (on road) will brake all four wheels if slippage occurs, whereas ATRAC (off-road) I believe will allow continuous wheelspin to at least one wheel (while braking the opposing wheel across the axle) on the front and rear axles to allow the truck to regain traction in off-road conditions. IE, if the right-front and left-rear wheels are off the ground, ATRAC will apply braking force to those wheels, but allow the left-front and right-rear to spin freely in the dirt/mud/sand/rocks to gain traction.

    Oh, and BTW, the 4R up to 2000 and the current FJ Cruiser has a rear locked diff option. The old 4R had no VSC/TRAC/ATRAC though, whereas the new FJ does have that too. But, only the 6 speed FJ has the full-time 4WD (Hi, Hi w/ center diff locked, and Low w/ center diff locked) with center diff (rear diff lock is standard), whereas the 5-speed auto version has only a part-time 4WD with no center diff (2WD-Hi, and 4WD-Hi and 4WD-Low for off-road conditinos with the rear diff lock being optional).

    This is my understanding of the system. Everyone got all that? :D
  • ccarofknowldgeccarofknowldge Member Posts: 19
    I think we need to get the guy who designed these systems to give us a lecture by posting. :-)

    Okay, um, I know that 4Runner has two different transfer case options. In the V6 the transfer case can be set to rear wheel drive (2WD). Toyota for some bizarre reason calls this a part-time system. This is very confusing for the reason that older 4wd systems in many SUV's and pickups had no center differential at all and thus could only be used on slippery surfaces to avoid axle bind-up and tire scrubbing. That no center differential system was called part-time 4wd because it could only be used part of the time (snow days and mud festivals). Toyota's part time definition simply means that you can use rear wheel drive if you choose to, not because you have to. Toyota's part time system does have a center differential.

    The V8 4Runner has a full time system which toyota means to say that you cannot operate in rear wheel drive or front wheel drive alone. Everyone else in the industry calls this (AWD) All Wheel Drive.

    Now chiefjojo are you saying that Trac is for the "part time" transfer case and ATrac is for that "full time" transfer case ???
  • wwestwwest Member Posts: 10,706
    Anytime the center diff'l or transfer case is locked the vehicle should NEVER be driven on a tractive surface. That's where, and only where, the term "part-time" comes from.

    It gets really confusing when vehicles like the 4runner are equipped with both full-time AWD and part-time 4WD/4X4 modes.

    AWD systems seem to come in three "flavors" currently, a fully open center differential with the brakes being used to prevent wheelspin/slip and thereby apportion engine torque, ue of a VC to "partially" lock the center diff'l with wheelspin/slip, and of course the Torsen center differential.

    4WD/4X4 systems, in general, always use a locked center differential and therefore constitute Part-Time systems since they cannot be used, should NEVER be engaged, on tractive surfaces.

    My own personal differentiation of 4WD versus 4X4 is that the 4X4 uses a transfer case, planetary gearset, so a low gear range can be provided.

    ABS functionality is ALWAYS disabled in Part-time, locked center differential, mode. We all know that during braking the weight "shifts" toward the front and therefore the front brakes take on the "brunt" of any braking effort.

    That means that during braking the front wheels almost always turn slower than the front. If the center differtial is locked then ABS activity at the rear would result, by default, in the same activity on the front.

    Therefore I would be VERY surprised if traction control isn't also disabled in 4WD/4X4 mode. With the center differential locked traction control braking at the front would also result in braking control of the rear driveline.

    Insofar as VSC is involved some aspects may be disabled (rear braking to aid in recovering from understearing comes immediately to mind). While front differential braking, or "unbraking" to prevent over-stearing might remain enabled.
  • 2toyotas2toyotas Member Posts: 104
    Sequoia, 4Runner, and Land Cruiser all use ATrac and Highlander, and Rav4 use Trac. The only difference is Low Range. ATrac changes from gradual fluid pressure control for stability-priority in High Range on all 5 that I mentioned, to sudden fluid pressure control for drivability-priority in Low Range. The second mode is for rugged offroad driving. The Highlander and Rav4 do not have a Low Range so they get plain Trac. When the center differential is locked in either High or Low engine output is not reduced as it is in the unlocked mode. Also when in Low range and in 1st gear there is gradual fluid pressure to the front wheels to keep control going down hill.

    On the FJ Cruiser Trac operates in 2WD or 4WD high, but shuts off in Low Range. In Low Range you have an option of both ATrac and a locking rear differential, both are engaged by a switch. When you lock the rear differential, ABS and ATrac are disabled. Two interesting things, when you lock the rear diff. ATrac does not work, so the front has only an open differential. Second you can now shut off ATrac, will we see this on 4Runner, Sequoia, and Land Cruiser? The rear diff and ATrac are an option on the FJ, but come together. So you either have both or nothing.
  • 2toyotas2toyotas Member Posts: 104
    ABS always functions with the center differential locked on all Toyota vehicles. Traction Control also works when the center differential locked. VSC is disabled when locked. The only time ABS and Trac turn off is if the rear differential is locked, and that is only on the FJ Cruiser and the Tacoma.
  • ccarofknowldgeccarofknowldge Member Posts: 19
    2toyotas, you write about fluid pressure, but the center differential in the 4Runner is a Torsen type which is all mechanical with worm gears and worm wheels. There are no viscous limited slip units on any of the 4Runner differentials, nor are there any clutch-pak limited slip differentials on the 4Runner.

    So, are you writing about the brake fluid being pumped by the abs pump as controlled by the ATrac system ???

    Toyota should have just used Torsen diffs on the front and rear to minimize confusion on this forum :-)
  • 2toyotas2toyotas Member Posts: 104
    Yes brake fluid being pumped by the ABS.

    I had a Hummer H2 that I borrowed from a friend for a week, and it has Torsen diffs on the front and rear, and it was horrible on ice. I was driving it one night and it was slipping all over the place. When I got home I had a very hard time getting it up my steep driveway. When I finally did I was curious so I backed my 4Runner down and it went up with no problem at all. The traction control kicked in, did its thing and I didn't break stride. A torsen diff is good in the center because it keeps power going to both axles all the time without it being locked, but I prefer traction control controlling side to side traction especially for snow and ice. The Sequoia had all open diffs until 2005. I had an 03 and an 05, and the 05 with the Torsen center diff made a big difference. Also the Highlander had a Viscous center diff from 01 till 04. In 04 they took the Viscous out of the center and used an open diff with Trac. For 07 they are going back to a Viscous center diff, so it must be better to have a limited slip unit in the center, this way both axles are always getting power.
  • ccarofknowldgeccarofknowldge Member Posts: 19
    Thanks for the reply 2toyotas. Seems like Toyota does its homework well :-). During the time when I had a vehicle with a viscous slip limiter working in conjunction with the center diff and a viscous slip limiter working in conjunction with the rear, I drove in snow and ice and never got stuck or fish tailed. When I first got it I tried taking off hard on snow and ice in a deserted area (with nothing to hit :-) ) to see what would happen. Absolutely nothing other than the vehicle just went where I wanted it to. Safe to the point it seemed like I was on dry pavement.

    From what I have read, the "Trick" with the Hummer and other vehicles that have Torsen's on front and/or rear that are not "pre-loaded" (a designed in drag to compensate for one of the design anomolies during a zero traction event) is that when you are trying to get up an icy driveway or out of an icy parking spot, you have to two foot the brake and gas simultaneously. The drag of a small amount of braking action while accelerating causes the Torsens to avoid that zero traction anomoly and do their thing. I have never had the pleasure to try this personally with a Torsen diff, but I need to do it on one of my clutch pack diff vehicles and it does seem to work as described.

    Next time your friend gives you a turn at the wheel, give it a try and let us know if the theory from the Hummer instruction manual actually works in practice on the vehicle.

    Incidently in this month's Four Wheeler mag they put Torsens into a project vehicle for mud and dirt and their review was that it was better than a "locker" for those purposes.

    Thanks for all the helpful info.
  • wwestwwest Member Posts: 10,706
    For the aforementioned reasons NONE of the braking related functions, ABS, VSC, Atrac, Traction, etc, will be enabled with the center differential locked.

    I have now read almost all, if not actually all, owners manuals of related vehicles (4runner, Sequoia, GX470, etc,)and in no place did it relate that these functions would be active with the center diff'l locked.

    Being well aware that doesn't cover the issue well I did find one statement saying that if the traction control's engine dethrottling mode interfered with vehicle manuverablity then the driver could lock the center diff'l to avoid engine dethrottling.
  • 2toyotas2toyotas Member Posts: 104
    Wwest I don't want to go back and forth with you but I own an 05 4Runner, an 05 Sequoia, and an 05 Tundra and ABS works on all three with the center diff locked. The Tundra does not have Trac and VSC, it only has ABS. It also is only part time 4WD and ABS still worked in 4WD. On the other two VSC does not work, but ATrac and ABS definitely work. Toyota would never leave their SUVs with open diffs when the center is locked, that would be pretty dumb. When the front or rear diffs are locked on an axle then ABS can not operate, but Toyota doesn't offer that.
  • neensawneensaw Member Posts: 4
    My 1997 Rav4 was accidentally put in C. Diff Lock, while I wasn't driving, (therefore not beeping) Having NO idea what the differential lock actually was, I of course kept driving. (This being my first car, and me being a teenager with no idea what I'm doing.) Now, after trying to take the Differential lock off, it won't stop beeping. Is it unsafe to continue driving while my car beeps? (The beeping is supposed to indicate that the Differential lock is still unlocking, but usually only takes 1 minute at most)What have I done!!!! Please give me some insight! :sick:
  • chiefjojochiefjojo Member Posts: 39
    I have 4Runner and when I unlock the center diff, I make sure I am in neutral or park first. Then as it blinks, either wait a few seconds for it to unlock or a trick is (while stationary) to switch between neutral and drive until it kicks in and stops blinking. If the center diff lock is still on, you should have noticed a lot of binding in the drivetrain (vibrations and difficulty steering) when driving on pavement, which can cause damage to the vehicle. Do not drive it if at all possible until you can unlock the center diff. I would say if this trick doesn't work, call a mechanic.
  • fkozilfkozil Member Posts: 65
    I recently acquired a '98 tacoma 4x4. The 4x4 system is not working. I jacked up the rear about 2-3" with a floor jack and engaged the 4x4. No 4x4 light came on and the truck would not drive off of the jack. The only wheel turning was the right rear. I tried the rear differential lock as well but had no luck. The locking diff. light flashes on the dashboard. Then I put the truck into 4 low. The rear diff. lock was then working as both rear wheels were turning and the light for the locking rear diff. stayed on however the truck still did not drive off of the floor jack. The front hubs are automatic and self-engaging. Any suggestions/comments are welcome.
  • ccarofknowldgeccarofknowldge Member Posts: 19
    I am not knowledgeable in the '98 tacoma 4x4 in particular but I can tell you that it is my understanding that automatic and self-engaging front hubs need to be turning in order to lock in. I realize this sounds stupid because if you are stuck on ice or snow and the front wheels are stationary because the rear has no traction and is spinning wildly you're just stuck looking for someone to push or tow you out. :-(

    On many, but not all vehicles, 4 Lo locks the center diff. If yours has a separate center diff lock, you need to turn it on to complete your test.

    HOWEVER, I WOULD NOT RECOMMEND TRYING TO DRIVE OFF A JACK. YOU'RE RISKING INJURY AND/OR VEHICLE DAMAGE. If your transfer case is not working right, you need someone with a lift and the factory diagnostic steps to safely figure this out.

    Good luck and stay safe.
  • ccarofknowldgeccarofknowldge Member Posts: 19
    Hi wwest,

    I got a response from Toyota and they said that the Center Differential Lock and the ATRAC system can "both be engaged at the same time."

    I asked them specifically about the 2006 / 2007 V8 Sport 4Runner, so that vehicle is the one they referenced their answer to.

    If you wish to ask them about your vehicle go to Toyota's website. It takes a long time for them to respond, so don't expect an answer for a while.

    Hope this is helpful to you.
  • toyodavetoyodave Member Posts: 7
    I have a 3rd generation 4X4. Auto Trans. The smaller of the 2 shift levers has a button on the side which allows me to go into 4 wheel drive at just about any speed up to 60mph. When I am in 2 wheel drive and press this button in, the light flashes on the instrument cluster, until 4 wheel drive "kicks in" at which time there is a muffled clunk noise, and the four green lights come on indicating "You are now in 4 wheel drive". Here's the question. Sometimes it takes 5-10 seconds for this little process to occur, and other times it doesn't seem to want to work at all. Whats going on here? Is there a grease fitting that lubricates this process? Why will it not go into 4X4 or at least takes
    its sweet time. PS. I try to "exercise" this procedure every couple of weeks or so. Should I be doing this more regularly? Thanks for any help. As an aside.....I Love this machine, it is so solid, reliable, good looking, and tough. I will never, ever, ever buy another north american made domestic vehicle, GM, Ford, Chrysler....they are flashy, but underneath and inside, they are all crap. Thanks.
  • chiefjojochiefjojo Member Posts: 39
    Toyodave, you must have a 99 limited model, which has the same 4WD system as my 02 SR5 model (minus ATRAC and VSC). In my experience the process you speak of is normal. When I shift into AWD (ie, 4WD w/ center diff unlocked) the light on the dash usually blinks for a few seconds and then there is a "muffled clunk" as it engages, as you said.

    If you are stationary, and want to shift in AWD, you can (1) press the 4WD button and shift the tranny into neutral and back to drive--this often helps engage and disengage the system quicker. If you are moving, you can either carefully follow step 1 or you can (2) blip the throttle on and off until it engages while driving in a straight line (I believe the manual recommends driving straight). The throttle blip technique has worked for me, but it can take 5-10 sec to engage.

    Just last night, I used step 1 (shifting in to neutral while parked), and it worked like a charm--took about 2-3 sec. I usually try to do that if I know I am going to be driving in the rain or snow, and leave the moving engagement of the system for the more rare occassions when weather conditions change while I am driving.

    Again, this is my own experience over the last 4 years of ownership. I hope it helps.
  • toyodavetoyodave Member Posts: 7
    Thanks for your reply. I will try this technique next time I drive my 99 4Runner. I discovered another thing last week that helps it get into 4 wheel drive, and that is if you turn the wheel like your going to turn a corner, either left or right, (while the yellow blip is flashing on the intsrument panel), it also helps the 4 wheel drive to "kick in". I wonder if some gear or spline has to align "just so" before it will engage. If you didn't use your 4 Wheel Drive for a year I wonder if it would ever work again or what? Happy Driving
  • curlewcurlew Member Posts: 5
    I couldn't find this particular system explained - everthing seems to revolve about the TRAC system...

    I have a 2000 4Runner Limited with the button on the 4WD lever that allows you to engage what I _think_ is an AWD mode. I _think_ this has the 3 open differentials (please correct me if I'm wrong - the manual is completely useless here), but this vehicle doesn't have the TRAC feature installed on LCs of that year and 4Runners starting in 2001.

    So...in 2WD mode, with an open rear differential (I don't have the locker anyway), in a low traction situation power goes to the wheel that's spinning, and you go nowhere. Now...putting it into this AWD mode, I extend this metaphor so that if either rear wheel slips, all of the power is transferred to the rear - and to the wheel that's slipping by the rear differential - and...well, you still go nowhere.

    If that's true, then it seems like the reverse would be true - if a front wheel were slipping, all the power would go there.

    And that's simply ridiculous - this system would seem to transfer all the power to the wheel that has no traction! Obviously, I'm missing something important here.

    Assuming someone can explain what my AWD system does (I think I've got a handle on the part-time 4WD part), I then have a followon question ...if one wheel is slipping (in snow, for example), what would be the effect of lightly applying the brake _and_ the accelerator? A light brake would stop that spinning wheel, right? Effectively a manual TRAC system?
  • toyodavetoyodave Member Posts: 7
    I think what you're missing is this. With 4WD engaged, the rear wheels are not linked together so they will spin. However, I beleive during this time the fronts are locked together, that is to say, left or right front can't just spin away without the other on the same axle, turning also. Where it starts to get really good is if you have rear "diff lock". Your press that button (usually on the dash) and it locks the two rear wheels together, and now you have drive to both front and back wheels, and the wheels on the same axle are locked together, and therefore, no wheel spin, and it will be mighty hard to get stuck. Does this answer it?
  • curlewcurlew Member Posts: 5
    Well, it answers it if that were true. But you're saying that the front is "locked" in AWD? That just can't be true either - locking the front would make it impossible to turn since the outer wheel would travel farther (same issue as locking the center differential on pavement and then turning). Unless the front were a LSD rather than an open differential, or there were some other spin sensing mechanism like the brake thing. And we're talking normal everyday driving here, not loose conditions - so there should be (and as far as I can tell there is) no detectable difference in "normal" conditions.
  • toyodavetoyodave Member Posts: 7
    You may be right about the front wheels not being "locked", and perhaps this is to enable you to steer......but, I know for a fact the rear wheels are "locked" because the manual says max 5mph, and not on dry pavement, and of course you can feel it. If as you say the front wheels cannot be locked together then.....how can you prevent the fronts from spinning on ice mud or snow? I still contend they are locked together, perhaps with an LSD. My original query to this discussion board was "why does it sometimes take so long for the 4WD to kick in when selected via the electronic push button on the 4WD stick?" Do you know the answer to that one? Thanks.
  • wwestwwest Member Posts: 10,706
    "..why does....."

    Because a "dog-clutch", spline type, coupling is used to lock the center diff'l. The splines must first line up perfectly in order for the shaft to slide into the lock position.

    SOP, nature of the beast.

    A slow creep will generally rsult in a quicker lock-up, and I sometimes had to put my Jeep in reverse.
  • toyodavetoyodave Member Posts: 7
    Oh Ok. You know more than you let on. That's the first decent explanation I have had of that question....Thanks !!!!
  • harboharbo Member Posts: 136
    So what is the easiest way to "switch off" the TCS to avoid having engine power cut back when in soft sand, mud etc, that effectively guarantees you will sink? 35 / 40 MPH in shot sand conditions allows you to stay on top and keep moving nicely with a bit of slippage, but not much. When the engine power cuts off the vehicle sinks and now you have a real mess. "Computer intelligence" is an oximoron when you know how to drive.

    THX for your advice.
  • curlewcurlew Member Posts: 5
    The manual cautions against the dry pavement only when the center differential is engaged (4HI and 4LOW), not when the AWD mode is engaged.

    I see you got a reasonable answer to your delay question, but I hope someone can pipe up with a reasonable explanation of ho this AWD mode operates in pre-1991 4Runners. And whether my question about lightly riding the brake would be somewhat analogous to what the TRAC system does.
  • wwestwwest Member Posts: 10,706
    TCS disable.

    Simply unplug the ABS pumpmotor, or remove the fuse.
  • curlewcurlew Member Posts: 5
    Egads - no response? Nobody knows how this AWD system works? I see I said "pre-1991 4Runner" in the previous message, but that actually should have been "pre-2001". Clearly that makes a difference...
  • harboharbo Member Posts: 136
    Anything else that gets cut off?
    THX
  • wwestwwest Member Posts: 10,706
    Yes, ALL the functions that require that the ABS pumpmotor be operational....
  • chiefjojochiefjojo Member Posts: 39
    So what is the easiest way to "switch off" the TCS to avoid having engine power cut back when in soft sand, mud etc, that effectively guarantees you will sink?

    Lock the center diff and the system will still allow some wheelspin (by wheels that have traction) in sand and mud... no need to pull any fuses. I have an '02 model with ATRAC and it gets through sand and mud just fine. A lot of FJ owners actually PREFER ATRAC to using their rear locker. :surprise:
  • harboharbo Member Posts: 136
    My 02 2WD Sequoia has the nuisance power cut back as soon as wheel spin is detected, causing the vehicle to sink in soft sand, mud, snow etc., just when you need to maintain momentum. What is the easiest way to "switch off" this idiot computer control?
  • wwestwwest Member Posts: 10,706
    Unplug the connector to the MAF/IAT module while the engine is running, plug it back in, restart the engine and now you will have a CEL and VSC/Trac failure indication that will extinguish after a few drive cycles. In the meantime VSC/Trac will remain disabled.
  • bmansfieldbmansfield Member Posts: 1
    2000 4Runner, 4WD but no buttons, just H2, H4, L4 on transfer case. This afternoon got stuck in deep snow, shifted to H4 ... right front wheel spun and rear wheels did nothing nor did the left front. I don't know what's going on here but it seems pretty useless to send all the power to one spinning wheel, leaving the other three with no power. For reference, the only "button" on my shifter is the overdrive switch on the main (auto) transmission shift lever. What am I missing?
  • dreasdaddreasdad Member Posts: 276
    Did you shfit down to L4? Thats what you would need in that type of road. Right front tire was proably higher than all the others so had less wieght on them.

    Can't rember if the 200 had a center diff loack or rear diff lock but button woul dbe on the dash not on the gear shift.
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