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Toyota 4WD systems explained

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Comments

  • wwestwwest Member Posts: 10,706
    Torsen vs VC

    Most importantly, the torsen (center differential) does not lock or inhibit speed differences during braking, thus allowing all 4 wheels to rotate independently at their own speeds when no power is applied. The torsen diff'l only locks in a power application situation while the VC locks during acceleration OR BRAKING. The torsen has a torque sensing characteristic while the VC has a rotation sensing characteristic.

    The VC's rotational sensing characteristic initially caused lots of problems for the engineers. Electronic anti-lock braking systems, ABS, rely almost entirely on speed differences between the four wheels to detect a locking wheel. Thus, when the VC tries to force all 4 wheels to turn at the same rate, during moderately heavy, or severe braking, it creates serious difficulties for an electronically implemented ABS system, and since it would telegraph the front wheels' (slower) rolling rate to the rear wheels it might cause loss of control of the vehicle.

    The engineers had to use a variety of HACKS to get around this problem. Mitsubishi delayed ABS for awhile for its first generation GSX, then finally decided to make ABS and rear VC limited slip mutually exclusive options. The VW syncro system simply disconnected 4WD the moment the brake pedal was depressed via a secondary clutch. Most other vehicles using this implementation of VC have a very simular disengage feature. The very successful World Rally Championship Lancia Delta Integrale even went so far as to apply a bit of power (via the engine ECU) to reduce the drag of the VC when the brakes were applied! Some very crude (sophisticated?) VC systems used an overrun device (Chrysler T&C) conceptually simular to a bicycle crank. This meant that while 4WD was disengaged during braking it was also inoperative when reverse was engaged! (The T&C overcomes this VC implementation flaw by adding a dog-clutch to lock the over-running clutch in reverse).

    The easiest VC "HACK" was to

    REDUCE THE EFFECTIVE VISCOSITY

    of the fluid in the VC coupling, so that it never (NEVER{?}) "TELEGRAPHED" the front wheels' rolling rate to the rear wheels, possibly causing them to lock up and cause loss of vehicle control, and ABS could still perform its task, rather than have the more heavily braking front wheels "dictate" their rolling rate.

    This also meant that the VC's "normal, and overall locking effectiveness was reduced, in some cases significantly so, but that might be quite acceptable for a vehicle used primarily below the snowline and never off-road.

    The VC's "attraction" is its simplicity and cheapness, not it's sophistication.

    Lexus RX300 AWD.. CHEAP ??!! NON-SOPHISTICATED ??!!

    None of this tells us why the RX300, with an open center diff'l but with a FLACCID VC, still remains predominantly FWD.

    But...

    Any questions class?

    Original document prepared by Eliot Lim.
    Editing by WWEST
  • wwestwwest Member Posts: 10,706
    I have seen a site explaining the need for a viscous fluid for these applications, VCs) that more dramatically increases its volume with increasing temperatures, including graphs of the rate of volume increase of some fluids vs others. I think the conclusion was that silicon based fluids of various formulations had the most dramatic increases in volume.

    Sorry, I don't remember the specific site.
  • cliffy1cliffy1 Member Posts: 3,581
    We're about to get our first snow as well down here in VA. Let me know how it works out for you. I own a Tundra and am still hopeful the 2003 model will include the Active-Trac system. My lease expires in November and the timing would be perfect.
  • spdmtr5spdmtr5 Member Posts: 111
    I would like to have some of the viscous fluid,place it in a pan, heat it,then determine if it really does thicken.Fudge does but then when it cools it sure doesnt thin down.And we are glad of that.
  • wwestwwest Member Posts: 10,706
    The viscous fluid will thicken with heat in the same way does the fudge, boiling off some of the liquid content.

    Do you like yours with walnuts or pecans. I vastly prefer pecans.
  • spdmtr5spdmtr5 Member Posts: 111
    Pecans!The only way.Could it be that the system in my wife's Trailblazer is really more reactive than a VC? I've not driven on ice-she has- and said it worked great.She used the 4awd position on the selector.The TB also has a LSD.
  • drmpdrmp Member Posts: 187
    "None of this tells us why the RX300, with an open center diff'l but with a FLACCID VC, still remains predominantly FWD."

    This is just a guess, I pressume the RX's traction control (part of VSC) is more agressive on applying the brakes to the rear thus quickly rerouting torque to the front. It is less agressive on braking the front since it affects steering and thus routing less torque to the rear on slippery situations.
  • spdmtr5spdmtr5 Member Posts: 111
    It may be that an increase in traction in the rear of a FWD car may cause more handling problems than increased traction to the front on a RWD;i.e. on the RWD if it's sideways additional traction to the front would tend to pull it straight,while adding traction to a front driver might skew the rear sideways.Pure FWD can be a handful on slick downhills.They want to rotate around the weight mass up front and you can't add any power with your right foot to control the slide.
  • wwestwwest Member Posts: 10,706
    In the past I have proposed that TRAC is only used right to left or vice versa, never front to back, etc. Lexus "HELPS" has so far not been willing to confirm either way.

    My reasons:

    TRAC is an electronically implemented system with the only mechanical "time delay" being the time needed to pressurize the brake calipers. Lexus says that TRAC will activate on detection of "impending" wheelspin. The VC on the other hand works on a fairly long time constant, it typically takes many milliseconds to heat the viscous fluid through the friction of the disparately rotationing VC clutch plates. Additionally the on-set of the VC activity must be designed for a fairly long delay to prevent its activation during turning manuvers and to prevent undue interference with the ABS.

    So the VC's incremental activation is totally dependent on sustained disparate rotational rates of the two sets of clutch plates and this would never happen if the instantly acting TRAC were to be used to allocate torque front to rear or rear to front.

    More...

    Anyone ever hear of a front axle LSD?

    Both of my Jeeps had rear LSD and a part-time 4WD mode with a locked center diff'l. The thought of having a front LSD had never enterd my mind and I don't remember any sales document offering it as an option.

    I doubt that TRAC can be designed to function very well as LSD on the front axle. It seems to me that any left to right, or VV, TRAC activity on the front axle would provide such a horrid level of jerking feedback to the steering wheel that it would be extremely discomforting to many drivers.

    If not forewarned might they react to a suddenly jerking steering wheel in basically the same way people who first encountered pulsing brake pedals reacted?
  • drmpdrmp Member Posts: 187
    Front LSD. Yes, they are used by nissan cars and infiniti FWD cars (SE and touring versions). These however are not the mechanical clutch type but (drums roll please!) the VC type. If you wonder how a VC could be attached in parallel with the diff, it is still similar to the link I showed earlier. The VC's one end is attached to the differential casing and the VC's other end is attached to one of the axles. VC is ideal for FWD since it has negligible initial binding and has gradual increase in coupling torque in relation to differential speed. In contrast, the mechanical LSD has significant initial bind (60 lb-ft) and non-linear torque increase which can easily be felt in the steering wheel.

    Traction control. This can be fine tuned to equalize wheel speed on both sides thus acting as electronic LSD. I believe this feature is used by Audis, VW's and Volos. I haven't heard complaints about unfavorable steering effect/feedback due to traction control activation but I theorize that it can.
  • wwestwwest Member Posts: 10,706
    I hadn't heard about VC's as an LSD in the front, but I agree that the VC's performance parameters are probably a perfect fit for this application.

    As far as I know there is no ABS/VSC/TRAC system that can moderate, modulate, the application of any of the brakes, the brake is either fully applied or it is off. The only modulation is that which is implemented through the rapidness of the on and off cycling.

    Absent some way to moderate the brake fluid pressure to the front, front LSD with TRAC would result in the steering wheel "pulsing" in the same manner as does the brake pedal on ABS application.
  • drmpdrmp Member Posts: 187
    Viscous LSD has been used by Nissan for a long long time already. Subaru has been using them also for the center diff and rear diff.

    About electronic front LSD, you might want to test drive a passat or jetta equipped with such thing and experience it for yourself. Technology has advanced so much that it is possible to modulate brake pressure and maintain a desired wheelspin. Pulsation is so rapid and mild that it can hardly be perceptible.
  • pschreckpschreck Member Posts: 524
    Had about five inches of snow by the time I went for a drive. The Tracs system worked flawlessly for the most part. The only time it had any problem was when I drove onto a paved parking lot that exited up a steep hill. This is my uphill test lot. The exit that I use is a hill that I would say is at a 45 degree angle. If you have been to southcentral Pennsylvania you know the rolling hill terrain that I'm talking about. I drove about half way up the hill and came to a complete stop and then started from a stand still. The first time was on virgin snow and I had no problem. The Tracs kicked in and I easily rolled up the hill. The next time I tried it the snow had been driven over a few times by others with the same intention as me so it was now much more slippery. The Tracs had to work harder but was still able to get me up the hill. The third time I used 4L with center diff locked and was able to get up a little easier than the second try. I know it's not very scientific but it sold me on this system. As for normal driving, no problem whatsoever. I drove on main roads and backroads. Paved and unpaved. Uphill and downhill. The sound of the Tracs system is a little unnerving at first but you quickly get used to it. I would recommend this system to anybody. I works just as well as old time 4wd with the added benefit of AWD when on road.
  • cliffy1cliffy1 Member Posts: 3,581
    Glad to hear it worked for you! I'm still hoping the Tundra will be available with this system by the time my lease is up next year.
  • wwestwwest Member Posts: 10,706
    pschreck's report:

    Anyone have a report of this type for an RX or an HL?

    pschreck:

    Your Toyota is predominantly RWD right?

    Did your trac system act on brake, the front wheels at all, and if so what was the affect felt by the steering wheel?
  • wwestwwest Member Posts: 10,706
    Does anyone know of an aftermarket strut/coil spring assembly for the RX series (and HL?) that when installed allows enough clearance such that tire chains can be used on the rear?

    Is this something that an aftermarket supplier might be willing to custom fabricate?
  • hicairahicaira Member Posts: 276
    I'd think some cable-type chains would fit on the RX without a lift. You could always install temporary spring helpers if that's all you needed. Regardless, why would you want to put them on the rear if, as you have said again and again, etc., the RX is FWD biased? Strikes me that you would have much better traction (and steering control) if they were on the same wheels that most of the torque was going to. In fact, if you are correct, putting chains on the rear will only increase front wheel slippage. If you are going to go the route of chains at all, put 'em on all four wheels. Way I figure it, if I'm already out of the car crawling around in the dirty roadside snow, might as well chain all the wheels and fully take advantage of the AWD.

    Reading all this I am thankful that I have a simple AWD system: All open diffs with manual lockers.

    HiC
  • pschreckpschreck Member Posts: 524
    If I'm not mistaken the Sequoia is only RWD when the Tracs system is turned off. When turned on I believe the torque split is 50/50. Am I right about that cliffy? It sure feels that way. I can say that on wet or dry roads, on a windy day at highway speeds (70mph), the Sequoia handles better with the Tracs turned on.

    I think I recall feeling a slight thumping through the steering wheel, but I won't swear to it. I was very much caught up in the moment. I can tell you that the system is at least as effective as my old 97 K1500 pickups' old time 4WD system. I can't speak for the other Toyota systems but I can say that for my needs this is a choice system. You get 4WD with a low range that can be driven ANYTIME IN ANY CONDITIONS.

    I think that the best way to describe this type of system is to call it Part Time Rear Wheel Drive.
  • wwestwwest Member Posts: 10,706
    Even Lexus has now admitted that snow chains ONLY on the front of the RX can be extremely hazardous. In order to put on four chains two of those MUST be on the rear.

    The bottom coil spring support plate surrounds the strut and is within less than an inch of the tire tread surface. Even cable chains would have to be kept extremely tight so as not to strike this plate.

    And I can assure I will NOT be chancing that!
  • pschreckpschreck Member Posts: 524
    Sorry, but in my previous posts I should have said Active TRAC instead of Tracs. TRAC refers to the 2WD system. After consulting the Sequoia New Car Features manual I realized my mistake. I purchased this book some months ago after seeing it referenced on another site. It's really about as much as I need. At thirty-five dollars it's a deal compared to the price of shop manuals that I wouldn't understand or use to their full potential. It's unlikely that I'll be yanking out the engine or transmission in this truck. If anybody is interested, the publication number is NCF196U. Unfortunately, I don't have the phone number that I dialed to order it. Maybe cliffy can help with that.
  • wwestwwest Member Posts: 10,706
    Active TRAC

    Would I be correct in saying it has two distinct modes.

    1. Torque distribution, control, left to right or right to left.

    2. Traction control, exactly like conventional TRAC in this mode, applies brakes on wheels.

    Oh, forget it, cheaper to go buy the manuals.
  • pschreckpschreck Member Posts: 524
    This is the best way of saying it:

    cliffy1 May 16, 2001 2:59pm
  • wwestwwest Member Posts: 10,706
    I get every time I read that bit.

    If the sequoia has three open diff'ls, what is the need for pushing ANY button to engage 4WD, and then "waiting" for the gears to match up so it can "slip" into 4WD.

    I'll go read the book.
  • cliffy1cliffy1 Member Posts: 3,581
    Because the center differential is only a differential when the 4WD system is engaged. At all other times, power is only routed to the rear. If you buy the book, you will note the center differential has something that looks like a very heavy duty motorcycle chain which is used to engage and disengage the differential.
  • pschreckpschreck Member Posts: 524
    Are there any viscous couplings in the Sequoia? Maybe that is where this confusion lies between the Highlander and the Sequoia. I can believe that the Active TRAC systems are the same, but surely there are major differences in the diffs and the transfer case. I really don't think one can compare the 4WD systems in these trucks beyont the Active TRAC system.
  • cliffy1cliffy1 Member Posts: 3,581
    No, there is no VC in the Sequoia. It is a mechanical, open differential/transfer case. You are correct in noting that you really can't compare the two systems.
  • loma1loma1 Member Posts: 32
    The Sequoia works much like your 92 Jeep.

    1. Selection for two wheel drive

    2. Selection for four wheel drive, center diff open.

    3. Selection for four wheel drive, center diff locked.(Like a conventional part time system)

    Two things are different

    1. The Sequoia has traction control that utilizes the brakes to stop a spinning wheel.

    2. The center diff only locks when the transfer case is in low and the transmission is in L.

    You need to wait for the four wheel drive to engage because the gears need to line up to mesh, like with a gear based locker for a rear diff.

    Gary
  • wwestwwest Member Posts: 10,706
    (first "3")

    "3. Selection for four wheel drive, center diff'l locked...."

    (Second "2")

    "2. The center diff'l only locks....."

    Isn't the first instance above a NO-OP?

    This is one of the problems I have with cliffys explanation, if the center diff'l doesn't lock then you are still in full-time (open diff'l)4WD as in "A" 2.

    "MY" 92 Jeep Cherokee Limited had RWD, Full-time 4WD (pretty useless), Part-time 4WD, and Part-time 4WD LOW (otherwise know as "grunt and groan", never went there) The Part-time modes were so "named" because they could not be used full time within incurring serious damage to the driveline, and your knuckles.
  • pschreckpschreck Member Posts: 524
    What's a NO-OP?
  • wwestwwest Member Posts: 10,706
    No operation, no functionality, doesn't do anything.
  • pschreckpschreck Member Posts: 524
    I'm not quite sure what you're trying to say or what question you're asking.
  • intmed99intmed99 Member Posts: 485
    Hi, I currently in the market for the 4Runner.
    Question: Does the current 4Runner with Active TRAC have a 4-channel ABS or 3-channel???

    I know the earlier versions before ATRAC have 3-channel. With the incorporation of ATRAC, don't you NEED 4-channel to INDIVIDUALLY control the rear drum brakes???

    Also, the REAR axle of the 4Runner is the same as the Tacoma's, right??? What size is it??

    What is the size of the Land Cruiser's rear axle??
    Thanks.
  • pschreckpschreck Member Posts: 524
    My guess is that the 4Runner would have a 4-channel ABS system. I'm lost as to answers to your other questions. Good luck.
  • loma1loma1 Member Posts: 32
    This is very informative as to diff sizes and a little bit less so on the axles.

    http://home.off-road.com/~bibelheimer/diffs/diff_info.html


    In short the ring and pinion sizes are different between the Tacoma and the Runner so one diff won't match up to the axle on the other. 8" for the Runner and 8.4" on the Tacoma.


    I'm fairly sure that it's is a four channel ABS. Is there something special you're planning on doing?


    Gary

  • intmed99intmed99 Member Posts: 485
    It is important b/c if the ABS is 4-channel, then the ATRAC will be more effective...limiting wheel spin in ONE wheel and transferring torque over to the other wheel. If you have ONLY ONE channel for the rear wheels, then ATRAC works mainly by cutting power to the rear AXLE as a whole! This is much less efficient. Therefore, it is very important to know if it is 4-channel (2 front, 2 rear) or 3-channel (2 front, ONE rear).
  • steevr1steevr1 Member Posts: 5
    My RX300 now has 2,200 miles on it. I've started to notice a whine from the drivetrain coming from the rear. It only happens at a contant 42-43 mph. Anyone else notice this? Thanks.
  • wwestwwest Member Posts: 10,706
    Just returned from testing...

    2001 AWD RX300

    Only conclusive test indicates maximum torque to the rear is approximately 25% and TRAC does NOT activate for F/R torque distribution.
  • drmpdrmp Member Posts: 187
    Good observation. Be careful with those dyno testing, you might burn out your center diff VC. You mentioned earlier that it would take a very short duration to burn out those VC's.
  • robncoloorobncoloo Member Posts: 1
    I am going from a 93 Range Rover to a 97 4-runner. I have really no understanding of the 4wd system on the 'runner, can someone please explain it to me. My rangie has rear traction control, viscous coupling, permanent 4wd. please help me to understand the Runner. is there any Traction control?
  • stickman3stickman3 Member Posts: 11
    The wife just picked up a 2000 LC. Live in midwest...probably never see off-road action...it is her minivan...am I correct that it is always in 4WD? If we get hit with 6 -14 inches of wet snow should she "do" anything with the system?
    1) To get out of driveway into street?
    2) Once she is in street?
    Thanks in advance...the manual doesn't help a non mechanical kindo of guy.
  • cliffy1cliffy1 Member Posts: 3,581
    With the LC, there is really nothing that one would have to do for the situations described. Unless you're doing something more harsh than a run to the grocery store with 12 inches of snow, don't touch the system. Let it work for you.
  • jcnew4whlrjcnew4whlr Member Posts: 18
    In the last midwest snow, I was driving on unplowed streets, about 4-5 inches of snow. Had no problem at all going uphill, straight, etc. However, I noticed that when I was going into a sharp turn at the bottom of a hill, my Sequoia 'snowplowed' like any other car/truck I've owned.

    I was moving very slowly because it was a narrow street with cars parked on the side, and brakes were lightly applied. My question is, should the VSC have acted to counter the snowplow effect? If so, what could have caused it to stay idle? If not, in what snow conditions would it act?
  • wwestwwest Member Posts: 10,706
    brakes were lightly applied...

    Would have over-ridden the VSC ecu.
  • cliffy1cliffy1 Member Posts: 3,581
    The VSC uses brakes at the corners that require it to prevent slides. By using the brakes, you prevented the system from operating. I would suggest finding a nice empty parking lot covered in snow to test out your system. Get the feel of what it will and will not do under controlled conditions.
  • mustangman3mustangman3 Member Posts: 10
    I am in the process of purchasing a 2002 base V6 HL. I want the added traction of AWD. I reading previous post, I think I have the following options:

    1.) Do not order the limited slip or skid control and have a vehicle with just 1 front and 1 rear wheel actually applying power to the ground.

    2.) Order the limited slip and at least if one wheel slips, either front or rear, then limited slip will kick in, and the opposite wheel on the axle that slipped, will then place power to the ground.

    3.) Order the Skid Control, and the brakes will be applied to a wheel when it slips and power will be transferred to the opposite wheel on the same axle like limited slip, and if the vehicle is sliding at any angle, more braking will be applied to straighten out the vehicle.

    If this is correct, then option 2 or 3 is my best bet for added traction, and if I was to make sure the vehicle is more stable, then option # 3 is my best choice.

    Thanks
  • wwestwwest Member Posts: 10,706
    The HL/RX has three OPEN differentials, front/center/rear. With this configuration ALONE if any ONE wheel slips ALL of the engine torque goes to just the one slipping wheel.

    Rear LSD would sent some torque to the wheel opposite the slippng rear wheel.

    The TRAC portion of VSC/TRAC is used to manage torque distribution left to right and vice versa NEVER front to back, that's the purpose of the VC, viscous clutch, across the center differential.

    Lexus TRAC implementation, traditionally, will first brake a slipping wheel or wheels, and then dethrottle the engine almost immediately if the driver isn't quick enough lifting the gas pedal.

    From the way the "01" shop manual reads I suspect that in the case of a single slipping front, primary drive wheel, dethrottling is used instead of differential braking. Differential braking might inadvertently break a few peoples thumbs or knuckles.

    VSC includes a yaw sensor and a steering wheel position sensor and these are used to determine if the vehicle is following the desired line of travel. if the vehicle is understeering both rear brakes are applied (so says the manual), if oversteering then the outside front brake is applied, sometimes so moderately all you hear is a strange noise coming from the frontal area.

    The VC.

    Most VC implementations of this type are designed to quickly "tighten" up and "lock" the center differential if slippage occurs front to rear or vice versa. The VC implementation in the HL and RX are referred to as a "simplistic HACK" by the AWD experts such as Eliot Lim.

    The Chrysler T&C AWD, for instance, has a VC implementation that will actually come into play very quickly and will truly "lock" the center differential if that is what is necessary to fully eliminate front to rear slippage.

    But, if the center differential is "locked" (it never is, just "stiffened") and you apply the brakes severely or moderate heavy the rotation rate of the rear wheels are "locked" to the rotational rate of the front wheels and the ABS could not do its job to help you stop quickly while maintaining directional control. Remember that the VC would have stiffened only if you were on a low traction surface and the lack of ABS capability in this circumstance could be disastrous.

    To prevent this from happening the T&C has an over-running clutch to de-couple the rear wheels rotational rate from the front in a forward motion braking circumstance. But what about reverse? The T&C has a dog-clutch which engages automatically in reverse so the T&C remains AWD even in reverse.

    The HL/RX has neither of these so the conclusion must be that the HL/VC VC implementation is so "slack" or "flaccid" that it never becomes stiff enough to rise to the occasion. And that actually proved to be the case in a test of the RX on a four wheel dyno, it can only route a maximum of 25% of the torque to the rear in the very worse of circumstances.

    Additionally due to poor suspension clearance snow chains cannot be installed on the rear and while recommending snow chains ONLY on the front in the owners manual Toyota/Lexus readily admits that this configuration can be extremely hazardous.

    Bottom line is that you will likely get just as good "service" from a FWD HL/RX as a "pretend" AWD version.
  • drmperaltadrmperalta Member Posts: 58
    Wwest, you mentioned, "The VC implementation in the HL and RX are referred to as a "simplistic HACK" by the AWD experts such as Eliot Lim."

    Wwest, Eliot Lim was siting the Chrysler T&C AWD an example of having the "simplistic HACK" , and no mention on Toyota/Lexus AWD.

    RX300 and Highlander has front and rear open diff and viscous limited slip center diff.

    Each of four wheels always receive 25% power and slightly more power on wheels with traction whenever wheelslip occurs due to the viscous limited slip center diff. Traction control further help by preventing leak of power from a slipping wheel.

    You also mentioned "The Chrysler T&C AWD, for instance, has a VC implementation that will actually come into play very quickly and will truly "lock" the center differential if that is what is necessary to fully eliminate front to rear slippage."

    The Chrysler T&C AWD has NO center differential, it is a misnomer. It only has an over-running VC that connects the front to the rear axle.

    The front is the primary drive and receives 100% power at all times. If the front slips, the VC limits rotational difference between front and rear and thus sending some power to the rear. Engineers play around with different axle gear ratios between front and rear to fool the VC to send trickle power to the rear when there is no front wheel slip.

    Hope Cliffy would come in and clear this out.
  • wwestwwest Member Posts: 10,706
    I have the shop manual for the 2000 Chrysler T&C and for the 2001 AWD RX300, if you would like to come by and have a look for yourself you are most welcome.

    On a four wheel dyno set to "limit" the speed of the rear wheels the front wheels "ran away". Seemingly, "braking" the rear wheels with "friction", had no adverse affect on the engine driving the front wheels, and it only took about 5HP to limit the rear wheels to 20MPH. Obviously didn't push this test too far for fear of damaging the poor VC.

    And, Eliot Lim refers to a VC HACK as being one that is designed to be so "flaccid" it cannot interfere with the ABS in its fully "tightened" mode, that description fits the RX/HL design to a "T".

    And speaking of differing final drive ratios why does the RX and HL have differing final drive ratios front vs rear?
  • cliffy1cliffy1 Member Posts: 3,581
    I'd love to clear it up, but wwest will continue to muddle it. Allow me to put it this way: If your needs are for very light duty off road use, light to moderate snow, ice, and wet conditions, I would select the AWD Highlander with VSC. Personally, I think the VSC is the best thing to come along since sliced bread. If I needed something more potent, I would buy the Sequoia or 4Runner (actually, on the Runner, I would wait a few months to get the new one with a V8 or larger V6). Both those models have a much more heavy duty and effective 4WD system, but is clearly overkill for many consumers.
  • wwestwwest Member Posts: 10,706
    with virtually everything cliffy said in #250, the exception being larger engines.

    Survival in most "normal" AWD conditions is more a function of finesse, not more HP. Now if you are going to take it off into the woods then cliffy is absolutely right, the only thing that will help you get unstuck deep in the woods is horsepower, normally somebody else's though.

    Like Dr Moore(torque) has said, the better traction your SUV has, the deeper into the woods you can get before becoming STUCK!
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