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Toyota 4WD systems explained

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Comments

  • wwestwwest Posts: 10,706
  • wwestwwest Posts: 10,706
    The HL is NOT a snow and ice SUV.

    All of my information is gained from owning an AWD RX300 but Toyota has assured me that the drive trains are basically the same.

    You cannot safely use snowchains on the HL or the RX. There is not enough suspension clearance in the rear for snowchains. Toyota or Lexus will tell you that an extraordinary level of traction (snowchains only on the front)on the front vesus the rear can be extremely hazardous.

    The AWD version of these vehicles is front wheel drive torque biased, about 90/10 ratio measured on a four wheel dynamometer. There is a viscous coupling mounted across the center open differential that in theory could route a substantial level of engine torque to the rear wheels once front wheelspin develops.

    In theory that is.

    In order to keep the design simple and the manufacting costs low the viscous fluid within the HL/RX viscous coupling is formulated to have a very slow reaction time and a fairly low coupling coefficient even after the time constant has elapsed.

    In our testing it took several seconds of front wheelspin for the torque distribution ratio to rise to the maximum of 75/25 front/rear.

    If you're considering the purchase of an HL or an RX then IMMHO the FWD version with the VSC option will give you just as good snow and ice service as would the AWD versions of these vehicles.

    And more (s)miles to the gallon.

    For snow and ice take a really serious look at any of the Chrysler AWD minivans or the 03 4runner.
  • intmed99intmed99 Posts: 485
    "In order to keep the design simple and the manufacting costs low the viscous fluid within the HL/RX viscous coupling is formulated to have a very slow reaction time and a fairly low coupling coefficient even after the time constant has elapsed.
    In OUR testing it took several seconds of front wheelspin for the torque distribution ratio to rise to the maximum of 75/25 front/rear."

    Are you Car & Driver, Consumer Reports, or something??? Can i subscribe to your preaching???

    There has not been ANY problems with RX or Highlander in snow...except for WWEST's constant whine. Many people are VERY happy with HL and RX's performance in snow.
  • wwestwwest Posts: 10,706
    that the clear majority of purchasers of AWD HL or RX are perfectly happy with the vehicle, even those north of the "snowline". Even so, that doesn't make what I have said untrue or of no value.

    Some of us tend to look under the skin of vehicles we are about to purchase, or have purchased, and I see no harm in advising others, certainly those that bother to ask, as to what we have found there.

    And by the by, this evening I discovered that the new RX330 has tighter rear suspension/tire clearance than the RX300.
  • wwestwwest Posts: 10,706
    Looks to me as if you already have, no subscription fees, please.
  • cliffy1cliffy1 Posts: 3,581
    If you go back over this topic, you will see that very few people's real world experiences agree with wwest's observations. There certainly are better vehicles for snow and ice but the HL is no slouch.
  • sirfilesirfile Posts: 42
    There are as many holes in wwest's awd theories as there are in Sadaam Hussein's palaces!
  • wwestwwest Posts: 10,706
    as hard to define or find as Saddam's WMD?
  • jmummeryjmummery Posts: 11
    First of all. Who from Texas knows anything about snow and ice? I have seen snow in Texas and I just hid and watched the carnage from my hotel.
    Why does chain fitment mean anything about S&I performance? I live in Saskatchewan and we Have over 7 months of snow a year with plenty of ice and I have never seen chains on a vehicle that wasn't plowing(not really a Lexus job).
    Mr. West does a reasonable job of conveying useful information in a limited space. I have not seen any posts bashing him with any technical value.
    If you want to do well(go too fast) in snow, buy a conventional 4X4 or a Subaru style(AWD) and some Nokians and LEARN TO DRIVE.
  • wwestwwest Posts: 10,706
    The most common need for snowchains in recent years has been that man in the strange flat brimmed hat telling me I cannot proceed absent installing chains, and for some reason they are never willing to accept snowchains ONLY on the front.

    I guess I could give up snow skiing or visiting relatives over the Pass at Thanksgiving or Christmas and then I wouldn't need to carry snowchains in the wintertime.

    Unless we get another winter like 90 or 95.
  • pschreckpschreck 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 Posts: 10,706
    We'll find them all right. Now a political necessity.
  • intmed99intmed99 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 Posts: 10,109
    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 Posts: 3,581
    You crack me up.
  • pschreckpschreck 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 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 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 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 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?
  • jmummeryjmummery 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 Posts: 524
    You are correct. Sorry guys.
  • wwestwwest Posts: 10,706
    jmummery,

    Can you hear the applause ??
  • steverstever Viva Las CrucesPosts: 41,884
    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

    Moderator
    Minivan fan. Feel free to message or email me - stever@edmunds.com.

  • idahodougidahodoug 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 Posts: 10,706
    It would be best not to fan the flames regardless of which side you stand on. Please.
  • tidestertidester Posts: 10,109
    It would be best not to fan the flames regardless of which side you stand on. Please.

    Agreed!

    tidester, host
  • steverstever Viva Las CrucesPosts: 41,884
    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

    Moderator
    Minivan fan. Feel free to message or email me - stever@edmunds.com.

  • wwestwwest 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
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