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Toyota 4WD systems explained

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Comments

  • pschreckpschreck Member Posts: 524
    He has them. We'll find them. We'll win. He'll lose. The torture chambers will be closed and the people of Iraq will be free.
  • wwestwwest Member Posts: 10,706
    We'll find them all right. Now a political necessity.
  • intmed99intmed99 Member Posts: 485
    How do you know that i have not driven in snow before??? You know what they say about people who "ASSUME" things....
  • tidestertidester Member Posts: 10,059
    You know what they say about people who "ASSUME" things....

    You are assuming that the mysterious and ethereal "they" know what they are talking about. :-)

    tidester, host
  • cliffy1cliffy1 Member Posts: 3,581
    You crack me up.
  • pschreckpschreck Member Posts: 524
    Yeah, I keep forgetting that America is the bad guys in this war. I'm sure we'll plant some WMD in Iraq so we can say "Told ya so".

    Thank God Slick Willie isn't in charge.

    I can't help but notice that Hillary hasn't had much to say. I wonder why.
  • wwestwwest Member Posts: 10,706
    is in charge, Willie, Al, or Jr, the US looks bad enough to the rest of the world for us to have gone to war for no real reason. At this point I would advise ANYONE to "find" WMD!

    And speaking of gas/electric hybrid, they do make sense even if the bottom line gas mileage isn't stellar. Think of the NSX hybrid as an economical supercharger.
  • jmummeryjmummery Member Posts: 11
    Have you lived anywhere that has lots of snow during the lifetime of the vehicles that you said where not a problem in snow? Have you ever driven an RX or Highlander in snow?
    I merely stated that people from Texas should not comment on driving in snow because of their laughable level of knowledge and skill on this subject. The only thing laughable about my knowledge on snow driving is that I got more today. Yes, April six and more fresh snow.
  • intmed99intmed99 Member Posts: 485
    Congrats on getting snow again...do you want an award for that or something?? Have you noticed that ONLY WWEST complains of the RX300/Highlander's performance in snow?? Or wait, DO YOU OWN A HIGHLANDER OR RX300???? If not, then your knowledge is indeed VERY laughable!
  • pschreckpschreck Member Posts: 524
    wwest, I'm not sure what you mean by "find" WMD, but it appears that we did. You don't really believe that the US or the UK planted them, do you?
  • jaredmsdjaredmsd Member Posts: 127
    please.
  • jmummeryjmummery Member Posts: 11
    I have driven a Highlander in fairly bad snow. I do not, nor would I own a Highlander or any Lexus. I love Tacoma(and 4Runner for that matter). I have had both. There is a big difference between "automatic" 4WD and old fashioned 4WD, especially in snow where reactions are different than other mediums.
    I do not want an award for living in Siberia er. Saskatchewan and having to live with a very long winter.
    I do however think that my opinion on dealing with this kind of road condition should be revered over that of a Texan with nothing to back up anything he says. Seems to be a common trait among among Texans these days.
  • pschreckpschreck Member Posts: 524
    You are correct. Sorry guys.
  • wwestwwest Member Posts: 10,706
    jmummery,

    Can you hear the applause ??
  • steverstever Guest Posts: 52,454
    about Texans et. al. Anyone is welcome to post here, and it's not just snow that makes for slippery conditions. We just had a cricket warning in the paper here (I'm not making this up!).

    Steve, Host
  • idahodougidahodoug Member Posts: 537
    I'll thank you not to insult Texans, particularly given that current events lead me to believe that was also meant as a slight against our Texan President. The United States of America is doing our level best to assist the people of Iraq and it is no secret how our neighbors to the North feel about it (thanks for nothing, Canada). We're successfully doing something about the quality of life for people on this Planet while most want to sit on their hands. If you drive like you handle international relations then I would rather not share a road with you - snowy or dry.

    IdahoDoug
  • wwestwwest Member Posts: 10,706
    It would be best not to fan the flames regardless of which side you stand on. Please.
  • tidestertidester Member Posts: 10,059
    It would be best not to fan the flames regardless of which side you stand on. Please.

    Agreed!

    tidester, host
  • steverstever Guest Posts: 52,454
    This is more of a FWD vs RWD article, but I found it interesting:

    "Why did truck-based SUVs suddenly become popular just as Detroit shifted to front-wheel drive for its passenger cars? Was it (as anti-SUV activists claim) because the SUVs were exempt from various safety and economy standards -- or because the SUVs still had rear-wheel drive, with all its subtle satisfactions?"

    Why Front-Wheel-Drive Sucks (Slate)

    Steve, Host
  • wwestwwest Member Posts: 10,706
    Dear Sir,
     
    I think you missed an important point in your article, a very important point.
     
    Natural human instinct.
     
    Absent any training specific to the incident at hand, say like in an aircraft flight simulator, what does your mind tell you to do the very INSTANT things go wrong?
     
    Hesitate, think, ACT!
     
    In a RWD vehicle in adverse roadbed conditions when the rear end starts to come "about" (the most common circumstance in RWD) your natural instinct will cause you to lift your foot from the throttle. That, in turn, will result in the rear wheels going from being driven to providing drag on the vehicle, sort of like throwing an anchor out the rear of a boat floating downstream.
     
    Conversely, in a FWD vehicle on adverse roadbed conditions when it begins to understeer (the most common circumstance for FWD) your human instinct will still cause you to react in the same way, lift the throttle foot. Now you've just succeeded in throwing the anchor over the bow of the boat, applying front braking via engine drag, and you're likely to go from understeering to oversteering in a big hurry.
     
    Regardless of the result, as you can see, driving a RWD vehicle on adverse roadbed conditions will always be more benign than FWD. Again, absent specific situational training.
     
    Willard West
  • idahodougidahodoug Member Posts: 537
    Completely inaccurate.

    On a FWD vehicle at the limit of adhesion (thus it's sliding), stepping off the gas does not cause the rear end to break loose in a typical car (some racing exceptions). Why? The front contact patches were using X percent of their friction for the cornering force, and Y percent for the acceleration (forward or rearward) force before you let off the gas. After you let off the gas, they are still using X percent to corner, but now Y has diminished as the power from the engine is replaced by the much lesser amount from engine breaking. So, this is a relatively benign thing to do compared to a RWD car which we'll now look at.

    On a RWD car, the rears typically come loose into understeer at the limit (exceptions abound). Letting off the gas instantly transfers weight off the rear wheels, reducing available traction. If the car was already at the limit of the rear wheels, this will likely cause them to slide more and faster.

    I'm surprised you are not aware of this as you mentioned you are a Porsche owner. The Porsche 911 series - the signature vehicle of the corporation - has been synonymous with oversteer for over 20 years. The term "drop throttle oversteer" was coined for the 911 series, which had a nasty habit of oversteering rapidly and wickedly when the driver backed off the gas at the limit.

    So, RWD is far more dangerous when cornering at the limit. Having said that, it is also worth noting that my position is accurate in general, but it is possible to design a FWD vehicle that oversteers or a RWD vehicle that understeers.

    IdahoDoug (once a victim of 911 drop throttle oversteer myself, BTW)
  • wwestwwest Member Posts: 10,706
    It's rear engine AND rear wheel drive. Don't bring it into these discussions, it isn't comparable.

    And you're absolutely correct again, stepping off the gas does not cause the rear end to break loose, especially not in the FWD vehicle of your example.
  • steelcruisersteelcruiser Member Posts: 402
    go slower. Oh, and what about that polar moment of inertia thingy?
  • rorrrorr Member Posts: 3,630
    "Oh, and what about that polar moment of inertia thingy?"

    Okay, I'll bite......

    All cars (all objects for that matter) have a "center of gravity". Briefly, it might be described as a 3D balance point for the vehicle. The "polar moment of inertia" describes how the vehicles mass is distributed about the center of gravity.

    Example: Cars 'A' and 'B' both have perfect 50/50 weight distribution. The center of gravity would be located midway between the front and rear axles. But Car 'A' may have a larger portion of it's weight way out over both axles (large moment of inertia) while Car 'B' may have it's weight tucked in much closer to the actual center of gravity (small moment of inertia).

    Okay, now I'm gonna go out on a limb (I'll let idahodoug and wwest correct me when I stray); vehicles with large moments of inertia would tend to be more stable in a straight line and resist turning movements. Vehicles with a small moment of inertia, because the weight is tucked in close, tend to 'turn in' quicker. They are more responsive. They also may tend to swap ends quicker.

    FWD vehicles, in addition to the problem of poor weight distribution (typically around 60/40) have the majority of that up front weight over (or even in front of) the front axle. This tends to exacerbate the problem of understeer due to the large moment of inertia. On the other hand, a mid-engine car (Toyota's MR2 for example) typically has a fairly small moment of inertia which adds to the responsiveness of the car (and also a tendency to swap ends easily).

    Think of the old analogy of a spinning ice skater: the CG doesn't move but with the arms out (larger moment of inertia), the skater spins slower. Tuck the arms in close (smaller moment of inertia) and the skater spins faster.
  • wwestwwest Member Posts: 10,706
    a rearward placed moment of inertia does...

    Too many 911's in the borrow pit.
  • pschreckpschreck Member Posts: 524
    The link posted by hondafreak is some kind of spam garbage. You may want to look into it. He also posted to the Audi TT board.
  • steverstever Guest Posts: 52,454
    Yeah, and my cable was down ~2 hours and I was going bonkers not being able to delete his junk in SUVs. The hosts are cleaning up now; not sure what legal's done about it yet ....

    Steve, Host
  • pschreckpschreck Member Posts: 524
    Flogging sounds too mild.
  • kinnmankinnman Member Posts: 52
    Still trying to understand this system. Today I was doing some light offroad driving. We had quite a bit of rain, so I put her in 4wd just in case. So I'm driving along and all of sudden the road gets real "mushy", I start sliding back and forth and I'm in 6-9" of mud. Both the traction control and VSC systems kick in. I felt like I was playing a pin ball machine....grrr...beep beep beep beep...grrr....grrrrrr!. The vehicle starts slowing down, I give it more gas, however as the traction control kicks in, the engine fails to respond, and the vehicle continues to slow.....it reminded me of that episode of star trek where the shuttle craft is entering the dooms day machine....I'm now slowly being sucked into a large puddle of mud. Mind you I'm now in about 12" of mud. Just before I come to a complete stop, the vehicle starts gaining traction and appears more reactive to the throttle, I'm out and home free. I look down to see both the VSC light and Trac Control lights permantley lit. Any explaining on this? Did the system recognize the dilemma I was in and disengage?
  • wwestwwest Member Posts: 10,706
    it exhausted its brake pressure regenerating capability and simply bailed. To prevent the ABS pump from over-heating there is a time limit on the amount of time it can run. Your indications should extinguish after you restart and then drive normally about a hundred yards.

    At least that was the case with my 01 AWD RX.
  • intmed99intmed99 Member Posts: 485
    Remember to LOCK YOUR CENTER DIFFERENTIAL!! This will turn OFF VSC and also PREVENTS the engine from dethrottling. This will save your butt in deep mud.
  • pschreckpschreck Member Posts: 524
    When I was in DEEP snow this year, I shutoff VSC on my Sequoia. Once I did that, I had less problem with dethrottling. I guess the Sequoia's VSC thought I was fishtailing too much (not true) and cut back on the gas to help me control it. What was actually happening was that I was losing too much momentum to get up the hill through the snow.
  • kinnmankinnman Member Posts: 52
    Correct me if I'm wrong, but I believe the only way to lock the differential on the Sequioa is to drop it into Low-4. In this case I wasn't about to lose my momentum and come to a complete stop to engage Low-4.

    Again, this was not a planned happening. I was driving down a dirt road going about 25, when the road got "mushy". Within seconds, I was down to 2mph and in 12" of mud.

    wwest...thanks for the explaination. Shortly afterwards I turned the vehicle off, and upon re-starting, the lights were off.
  • shek3shek3 Member Posts: 72
    you can lock the diff in 4wd high also
  • pschreckpschreck Member Posts: 524
    kinnman is correct about the Sequoia. At least on the 2001 MY you can only lock the center diff while in 4WD Low. To lock it, you must also be in first gear.
  • servo_fanservo_fan Member Posts: 15
    I was reading the Edmunds 2000 Mid Sized SUV comparison and the 4Runner had a clutch-start cancel button that Edmunds described as a "feature catered to hardcore off-roaders". Would this be for starting the vehicle without the clutch engaged so that you get it lurching forward to get you unstuck? Thanks.
  • toyotakentoyotaken Member Posts: 897
    There are two situations that you might use the clutch start cancel. One is, as the article says, for serious off-roading. The starter motor has lower gearing then 1st gear with the engine running, so you could just use the starter motor to crawl your way out of a VERY difficult situation rather than riding the clutch.

    The second and more common use is for those who don't like getting all the way into the truck to start it to let it run and warm up. MAKE SURE THE PARKING BRAKE IS ENGAGED BEFORE DOING THIS!!!
    Push the clutch-start-cancel button, reach in and turn the ignition on, walk away. For those who warm up their vehicles before driving, it saved climbing in and out to start it.

    HOpe this helps.

    Ken
  • wwestwwest Member Posts: 10,706
    kinnman:

    Was that actually a Sequoia that you were driving when the VSC/Trac system shut down due to the ABS pump being over-taxed, or potentially over-taxed?
  • kinnmankinnman Member Posts: 52
    Yes, 2002 Sequioa 4x4. I was going for about 30-45 seconds where the traction control was kicking in.
  • wwestwwest Member Posts: 10,706
    That the Sequoia doesn't have a more robust ABS pump than the RX300. Now I worry about the RX330 using it for AWD implementation, the Sequoia has a "backup" AWD system once the ABS pump times out, the RX330 does not.
  • cliffy1cliffy1 Member Posts: 3,581
    I'm actually shocked. Toyotaken not only got it right, but also correctly described the most common use. The funny thing is, the "not getting all the way into the truck" use is not described by Toyota in any of our literature. It is one thing I have often described to my customers, and I may have described it years ago here at Edmunds, but I have never seen it in print. Good job. Are you sure you never took one of my truck training classes?
  • brightnessbrightness Member Posts: 40
    How does it compare to the Sequoia, Highlander, RX330, etc. Thanks
  • wwestwwest Member Posts: 10,706
    Seems to have the very same drivetrain and driveline setup as the RX330. "Virtual" AWD, using the brakes to apportion engine torque, like the ML and Sequoia.

    Trying to confirm with Lexus, but it appears there might be a 30 to 45 second limitation on brake modulation torque apportioning due to the need to protect the ABS pump from overheating.
  • steveb84steveb84 Member Posts: 187
    The "starting and warming up" use is how I explain it to my customers here in the upper Midwest also. (I learned it from my Toyota sales mgr when I started 7+ yrs ago)

    I guess great minds must think alike. Hehehe !!!
  • cliffy1cliffy1 Member Posts: 3,581
    I owned a 93 4x4 before I got into the car business. I learned that little trick myself. When a customer would ask me, "what's this do?" I would say, "Do you want the official answer or the most common use for it?"
  • idahodougidahodoug Member Posts: 537
    I've used this handy feature many times for its intended purpose - restarting a stalled manual in a hairy offroad situation. It works great and very smoothly to start the truck and is a favorite Toyota feature for hardcore offroaders.

    The starting when not in the car thing is not mentioned by Toyota because it is inherently dangerous. Either the customer left the car in neutral with the brake on and uses it this way (not the safest thing as it should be in gear for safety), or they may one day forget it's in gear and the truck will start and drive through the garage wall. Great feature, but one day it will disappear for this very reason thanks to some attorney somewhere. While I'm at it, another heartfelt "thanks" to the attorney who successfully forced Montana to eliminate their unlimited freeway speed limit (insert appropriate hand gesture here) a couple years ago. I used to make it across that 700 mile state in under 8 hours.

    IdahoDoug
  • wwestwwest Member Posts: 10,706
    Almost always, still do (in the daytime anyway), Great Falls to Lewistown in under an hour.

    Changing the law is one thing, forcing Montanans to abide by them and the law to enforce them is quite another.
  • steverstever Guest Posts: 52,454
    I thought Montana adopted limits to comply with federal regs so they wouldn't lose matching funds for highway construction. Or maybe that was back during the 70's gas crisis.

    Montana Autobahn

    Steve, Host
  • idahodougidahodoug Member Posts: 537
    You regularly cross Montana in 8 hours?? Are we talking about the same Montana? 700 miles-wide-Montana? You have to average just under 88mph including any stops! I did it several times using the cruise control at 94mph, stopping twice for gas. You might want to recheck your figures on that, because I don't think you're doing it these days.

    Steve - Montana indeed expressed their displeasure at the ludicrous 55mph speed limit in the 70s. They set the limit at 55 to remain eligible for the funds, but if caught you only got what was termed an energy resource fine of a few bucks. Then it was unlimited until a few years ago. Kinda fun, but you really had to pay attention at 94 as there are curves out there that even an Audi Quattro won't negotiate at that speed - so you really were not able to relax fully with the cruise on. One day, I missed a crucial gas stop in the LandCruiser and slowed to 55 for 20 miles to avoid running out of gas. I can therefore vouch that 55 would be incredibly frustrating in that state as a maximum.
  • mttownsend1mttownsend1 Member Posts: 2
    My '03 4 Runner shifts strange in 4 wheel low. The automatic shift between 1, 2 & 3 is very abrupt and in some situations off road could be dangerous. I've had 5 other SUV's and I've never had one that shifts with the abruptness and jerk that this one does. Have any of you experienced the same in yours?

    I have the V6 model, Sport Edition.

    Thanks
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