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Toyota 4WD systems explained



  • wwestwwest Posts: 10,706
    Worn tire(s), differentially worn tires, will most definitely have an adverse effect on the ease with which you can engage the center diff'l lock.
  • I am writing to see if anyone else has had the same issues I have.

    1.Once the vehicle is engaged in 4hi, the differential axle screws up and causes the vehicle to spin out of control even at low speed when turning corners. Vehicle wont switch in to 4 low.

    2. The radio. I've had the radio replaced once already and the second one is on the fritz. There are major electrical problems with this truck. Turn the lights on and your radio turns on, turn a corner and your radio turns off. I think Toyota has issued a band aid fix, telling owners that the problem is a defective radio, when the electrical system is to blame.

    I think its time for people who have been ripped off by Toyota to band together before someone gets killed.
  • beachfish2beachfish2 Richmond VAPosts: 177
    "and causes the vehicle to spin out of control even at low speed when turning corners."

    How many wrecks have you had? That's sounds terrible - spinning out of control when turning corners at low speed. Have you rolled it over yet? How many times?

  • wwestwwest Posts: 10,706
    Center diff'l locked and turning....

    Bad news, the worse, tighter, you turn with the center diff'l locked the higher is the potential for lost of directional control.

    Nature of the "beast".
  • I am currently experiencing a problem with my 2000 TLC - it seems to be stuck in 4wd - I have had the vehicle since 03 and have driven it 200k miles - now when turning short radius or backing into driveway the front wheels feel like they are locked into low 4 - tires squeal, feels like tire is flat, power steering feels under load . . . Any ideas? Thx!
  • sparklandsparkland Posts: 119
    This video pretty much shows why the Toyota Highlander and the Honda CRV, Ridgeline are inferior to the Suburu Legacy with respect to traction in poor conditions. It will make you mad!

    Neither Toyota nor Honda told us about this.
  • pschreckpschreck Posts: 524
    Greetings all. I haven't posted here in years. Used to be around when we had an 01 Sequoia. That truck is long gone and now I'm considering a Tacoma.

    Can anybody tell me if the Tacoma can be driven on DRY roads with 4Hi engaged like the 01 Sequoia could? Does it have the center diff like the other Toyota products that allow the 4WD to be used as an AWD system in the rain or partially snow covered roads? I'm not fond of the old part-time systems that lack the center diff.

    Thanks for the help.
  • wwestwwest Posts: 10,706
    In a word...

  • wwestwwest Posts: 10,706
    edited April 2010
    "...I'm not fond of the old part-time systems.."

    But they're the only ones that work, for sure work.

    And as it happens most are RWD with the system off, not patently UNSAFE FWD or F/awd.

    Those with a simple open center differential are only "pretend" AWD (4WD.??). Simple, simply ONE-WHEEL DRIVE using the brakes to allocate/apportion engine torque but only AFTER traction is lost.
  • pschreckpschreck Posts: 524
    Wow, you're still here. How many years has it been?

    No offense, but I won't be drawn into an argument of circular logic with you.

    My Sequoia's 4WD was wonderful for me. What works for you is another issue.

    Can anybody else answer my questions?
  • canddmeyercanddmeyer Posts: 410
    No. Do not drive the vehicle in 4wd on dry roads. You can drive in 4wd on wet or especially snow covered roads if there is slippage. Just don't make a habit of it. Center diff is fantastic. I'm sure many 2010 4Runner owners miss it already.
  • agnostoagnosto Posts: 205
    edited April 2010
    That is the main reason I paid extra to get the 2010 4Runner 4WD Limited for the awesome full time 4WD feature (hopefully there is no recall for the 2010 4Runner so far...)
  • wwestwwest Posts: 10,706
    "..paid extra...for the awesome full time 4WD..."

    From the way I read the factory documentation the newer 4runner's full-time 4WD system may not be as awesome as one might think, or buyers have been lead to believe.

    Toyota stopped using the "torsen" term to describe their 4runner 4WD system some years ago now. In addition the transfer case differential drawings are no longer broken down to show the internal workings of the transfer case differential.

    All that leads me to believe the 4runner's full-time 4WD system, at least the 2010 one, is a simple ONE-WHEEL DRIVE SYSTEM, just as the Highlander is and the RX series was until recently.
  • pschreckpschreck Posts: 524
    "All that leads me to believe..."

    Do you have any REAL facts to back up the statement? Are you guessing?

    I'm not saying you're wrong, but how is a person supposed to make a purchase decision based on some internet guys guess?
  • wwestwwest Posts: 10,706
    " is a person.."

    First, be aware that the salesperson doesn't know BEANS about the vehicle you are planning to purchase.

    Even worse.

    The RX330 was marketed as having a VC, Viscous Clutch, to help apportion engine torque to the rear with loss of traction at the front. The factory manuals indicated otherwise so I asked corporate who acknowledged, after I persisted, that the manuals were correct. I never saw an ad retracting the falsity.

    The RX350 was advertised as having the VC but again the manuals differed. I was never able to get a corporate response on the true of the matter.

    In point of fact when the RX series adopted VSC and TC across the product line in '01 the VC became useless even if included. The VC P/N for my '01 RX300 and the one for previous years is different so I suspect mine to be an "empty" VC case.

    If the 4runner doesn't have the Torsen center differential, only a standard open differential, how would an owner ever know? Get stuck, lock the center differential, drive away.

    PS: My '01 RX300 once spent 4 hours in the dealer service bay with the technicians trying to determine if the VC was actually still functional. End known way to test and corporate could not advise.

    The only way to determine functionality is on a 4 wheel dyno.
  • kingfans1kingfans1 Posts: 137
    hi west,
    what kind of awd/4wd vehicles do you recommend in snow?
  • onoffroadonoffroad Posts: 17
    On the Outer Banks of N.C. ! Their's signs saying 4WD not for AWD ! Guess some AWD are getting stuck !!
  • wwestwwest Posts: 10,706
    "..Guess some AWD are getting stuck !!..."

    No kidding, and even some that are FALSELY labelled 4WD.

    Lots of sins created under the AWD "term". Most are simple FWD with some minor level of part time, "automatic" part time, rear drive augmentation. With the rising public awareness of the patently unsafe nature of FWD vehicles for wintertime adverse roadbed the manufacturers are attempting a "bait and switch", "find the pea", sales technique.

    Any "base" FWD vehicle, sideways mounted engine, that has some level of rear drive augmentation should NEVER be referred to as AWD, nor even 4WD as some manufacturers seem wont to do.

    F/awd, awd only in lower case, is the only appropreate marketing designation, label for these patently unsafe FWD vehicles.
  • wwestwwest Posts: 10,706
    "..Guess some AWD are getting stuck.."

    The sign could be more definitive, narrow the restriction, if F/awd vehicles were kept out that make use of TC braking to implement some form of F/awd, apportion some minor level of engine torque to the rear via the use of braking at the front.

    Slow to a virtual stop, get stuck, TC instantly dethrottles the engine, call for a tow.
  • wwestwwest Posts: 10,706
    I find myself perfectly happy in "snow" with my F/awd '01 RX300 even running summer only tires....

    EXCEPT on ice or packed down snow. At that point I immediately install rear tire chains and add the fronts if conditions(***) warrant.

    *** Conditions might involve surrounding traffic, INCOMPETENT driver traffic.
  • wwestwwest Posts: 10,706
    On the other hand should, when, the transaxle in my '01 RX300 finally fails, expected prior to 100k miles, now at 80K, I will be converting the RX to R/awd.

    The center differential front drive spider gears will be removed and the rear drive spider gears will get welded into place. Eliminating front mechanical drive and SOLIDIFYING the engine drive coupling to the rear. I will also be installing a new VC from the 99-00 RX series so that torque coupling will automatically be coupled to the front upon/with rear wheelspin/slip.

    So, my preference is quite clearly some sort of R/awd system such as is in my '94 Ford Aerostar. In the absence of R/awd availibility I would always choose RWD, tire chains on board, for travelling on wintertime adverse roadbeds.
  • beachfish2beachfish2 Richmond VAPosts: 177
    I've been surf fishing the Outer Banks since the early '70s and it's more about knowing how to drive on the beach than it is the vehicle. We started out using rear wheel drive trucks with large nearly bald tires. Tread only aids in digging you into the deep, soft sand when a wheel spins.

    I haven't taken my '10 HL Limited out yet, but there were a few older ones at Cape Hatteras 3 weeks ago and they were getting around. It's funny having 19" wheels now, after driving an '86 Subaru GL wagon with 13" wheels on the beach for 14 years. It's all about ground clearance and letting enough air out.

    Take a tire gauge, a shovel, a board and a snatch strap no matter what you drive.
  • 2toyotas2toyotas Posts: 104
    The new Sequoia, land Cruiser, FJ with a stick, and Limited 4runner, all use a torsen center diff that can be used on all surfaces. The Tundra, and tacoma still use a part time transfer case with no center diff. I have a 2006 tundra and it is really good in wet conditions in rear wheel drive. I know what you mean though. I keep saying if they put a full time transfer case in the tundra I would buy a new Crew Max. So I keep waiting and hoping. But yes the Torsen is still being used despite what "SOME PEOPLE" say.
  • Don't go through all those 2000+ post. Please forgive me if someone asked before.

    Could some explain what the 4WD/AWD systems are in recently Toyota models? Are they full-time 4WD, full-time AWD, or just part-time/auto AWD? I am specially looking for Sequoia, 4Runner, Highland, and Sienna. The first post of this thread is from 2001 and lots things have been changed. Thanks.
  • stateofmainestateofmaine Posts: 30
    edited December 2010
    this will help you get started:

    please note that it is dated 1/09, so not all the model information is entirely up to date.
  • shangydshangyd Posts: 25
    edited December 2010
    Nice Tutorial. Thanks.

    did a little search and found the updated version:

    4Runner: no multi-mode 4runner. limited would be full-time 4WD. other 4runner would be part-time 4WD.

    Sienna: on-demand AWD.

    all bad things for me.
  • thanks for posting the link to the updated version. sorry it wasn't happy news for you.
  • wwestwwest Posts: 10,706
    The thing to keep in mind, REMEMBER, is that there is NO such thing as a FULL-TIME 4WD or AWD system for, in the manner, for which you wish to make use of one.

    Yes, the Highlander, for instance, has a FULL-TIME 4WD system, right up until you reach the point of actually needing to make use of 4WD traction capability. At that point, wheelspin/slip, any one wheel or wheels, the HL reverts to it's true nature and becomes a ONE-WHEEL drive system.

    Absent TC, Traction Control, capability you would now be STUCK...!!

    But while TC might often be your savior in this situation in many instances it will operate to your detriment. Which is why most F/awd systems have a TC disable switch.

    So be very careful of any Base FWD vehicle, crosswise mounted engine, that makes claim to having FULL-TIME "4WD" or "AWD" capability/functionality. What they most likely mean is that the "AWD" system is ALWAYS enabled, but only activates REACTIVELY once/after wheelspin/slip is detected.

    The 2011 Porsche Cayenne, and likely its VW & Audi brotheren, are about the only R/awd systems available that I know of. These can be both pre-emptive and reactive, with SAFETY.

    Pre-emptive in that like the new Sienna, Vensa, and RX350, they can and will automatically engage the front drive torque under the driving conditions which are most likely to result in loss of drive traction, low speed acceleration. But UNLIKE the Sienna, Vensa, and RX350 they have no need to REDUCE the drive drive torque during tight turns or acclerating turns since it is the rear wheels that provide the primary drive forces.
  • Good post, WWest. Always enjoyed reading your insights on this awd stuff.

    Got a question for you: we recently got an accord crosstour with "on demand 4wd". The system works by using a hydraulic circuit to engage the rear wheels when there is a speed differential between front and rear wheels during slip.

    The issue centers on the use of snow tires on dedicated rims...something we have always done for our cars.

    In this case, however, we have a tire pressure monitoring system, and making it work with the snows on their own rims involves not only outfitting the rims with sensors, but also "re-registering" the different sets of sensors with the car's computer....something that costs about $70 at the dealer twice a year. Not very attractive.

    Alternatively, Tirerack says about half of their customers just forget about the sensors with the winter tires and live with the TPMS warning light during the season.

    Only problem is that in this car when the TPMS warning light is on you cannot disengage traction control. Am I correct that disengaging traction control might be exactly what I would need to do to get myself unstuck in the snow?

  • mdhuttonmdhutton Posts: 195
    OK wwest - I haven't always agreed with your posts, but I've come to respect them. If you owned a 2008 HL Limited 4WD (gas), how would you operate it in Chicago's snow to get the best performance from it? Based on your responses, you would engage the SNOW button and turn TC off. Yes/no?
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