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Toyota 4WD systems explained

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Comments

  • wwestwwest Member Posts: 10,706
    Kumar...

     

    I think most of us refer to systems that actually lock the center diff'l as PART-TIME, because they cannot, should NEVER be driven on high traction surfaces with the diff'l LOCKED. Therefore PART-TIME, for use ONLY on adverse roadbed conditions rain, ice, packed snow, or off-road in poor traction conditions.

     

    Full-Time or Permanent 4WD systems simply run with the center diff'l open.

     

    AWD systems generally have some way of automatically locking, or "slightly" locking (viscous fluids) the center diff'l upon wheelspin.

     

    Many (most??) modern day AWD systems run with the center diff'l continuously open and use braking to prevent wheelspin and thereby maintain a high level of torque overall.
  • nedzelnedzel Member Posts: 787
    The 4Runner is full-time 4WD. The center diff is a Torsen diff. In shifts torque automatically. But you can also lock it in both 4hi and 4lo (only offroad or on slippery surfaces).
  • qualitynutqualitynut Member Posts: 36
    I have driven everything from part-time 4WD to AWD to full-time 4WD ('03 Cruiser) and my experience both driving and observing others driving on pavement is that:

     

     
    1) Most owners of part-time 4WD don't understand when NOT to be using the system. I have seen many crashes on freeway exit ramps, especially curved declines.

     

     
    2) Many AWD systems that utilize viscous fluids still bind while turning which is detrimental while on extremely slippery surfaces (ice). My '98 JGC w/QuadraTracII would still bind considerably while turning although not as bad as some others that have more forward bias. Unintentional resistance to rotation while on slippery surfaces can have extremly bad results!

     

     
    3) Open differentials w/stability and traction control is best in my opinion for the typical driver on paved roads (yes, I do understand that there may be better options for off-roading but that is not what I am addressing). The advantage of 25% torque to each wheel at time=0 is a huge benefit. I am always amazed at the difference and the fact that in many cases, I have to intentionally try to break a wheel free to even activate the traction control system.

     

    Why have a multi-wheel drive system when it isn't usable 99% of the time? The extremely limited benefits of part-time 4WD systems are being sold to the general public to their detriment. Varying quality of road surfaces makes these systems unsafe in most cases.

     

    - Eric
  • tlcmantlcman Member Posts: 220
    Im not sure what kind of 4WD systems you are seeing but a part time system that is turned on to 4WD will not jepordize a cars stability for example on a on ramp, Unless the center differential is locked which it usualy isnt, a Part time system engaged acts like a full time 4WD system except it can be turned off, and dont try telling me my full time 4WD jepordizes my driving, The thing about it is that you have power to all wheels when they all have traction, when one slips then all power goes to that wheel, close the center differnetial and you send power to one slipping rear and one slipping front tyre, add VSC and Trac control to the standard 4WD and it aplies a brake to that spinning wheel directing power to the others. I can give you a complete discription if you want it but somthing did not sound right about what you said. Manufactures are not otherized to sell equipment that is unsafe when used properly. And a 4WD system has been prefected to a point where that isnt an issue.

     

    If you GMC or what ever bravada was gripping in a turn somthing was wrong with it or they had the work peramiters, a Viscous coupler will not creat that, it works by spinning exesivly for front or back, and then gets tougher to create the "soft lock"
  • wwestwwest Member Posts: 10,706
    1. Equal engine torque delivered to all four wheels as long as a constant speed is maintained in a straight line.

     

    2. Engine torque is adjusted proportionally, increased, to the rear with stearing inputs, allowing the front tires' contact patch to be allocated to directional control.

     

    3. During startup or acceleration, as G-forces climb, proportionally more engine torque is routed rearward.

     

    4. During coastdown or braking, engine drag torque is routed only to the rear.

     

    Miss anything?
  • tlcmantlcman Member Posts: 220
    Thanks that was more simplistic than what I would have said! haha, If you all need me to explain though your probably going to be reading a very detailed book about it, that Im sure has been posted in this thread 3 or 4 times by now.
  • pschreckpschreck Member Posts: 524
    Maybe I'm not reading your post correctly, but all the Part Time systems I've owned locked the center differential when engaged. It wasn't until I got my 2001 Sequoia that I could be in 4WD without a locked center differential which means I can drive it on dry pavement, hence the Full Time classification.
  • tlcmantlcman Member Posts: 220
    First, What trucks automaticly lock their center diff in 4WD high?

    I think your talking about low, but part time systems can engage 4wd High too, or atleast in my opinion the good ones should.

     

     

    Thats fine but when you said that you had seen many bad wrecks on highway onramps it means that the person driving that car was not using their brains in getting on the inersate with their center diff locked, A four wheel drive system with an unlocked center differential but power to all corners will not make going down a curved on ramp a strugle for life.
  • wwestwwest Member Posts: 10,706
    A 4WD with diff'ls unlocked but with u-joints on the front, as many are equipped, can readily bust your knuckles in an accelerating turn.

     

    CV joints are wonderful, but even my 85 Jeep equipped with them could be a serious threat to my knuckles at times.

     

    And I think, the idea of only locking the diff'l is low range is a fairly recent developement. Likely a result of too many inexperienced owners driving inappropriately in 4hi locked mode. I could run both of my Jeeps, an 85 and a 92, with the diff'l locked, hi or low.
  • tlcmantlcman Member Posts: 220
    Im not sure where that came from, ok you bring up a point, one that Lockers will severly dmage them selfs above 10mph on high traction surface. I too can run my Land cruiser with Center Diff locked, but its not meant to be on High traction surfaces, if you are going over 10 miles per hour there is no need to have your lockers locked, they are for slow moving and getting over large objects or going through mud. Your U- joints will have a horrible amount of pressure on them if you are locked and driving on the free way on ramp, thats not a smart choice, Because it is a high traction surface, thats why the strain is there, not all Part time 4WD will lock the Center diff, turthfully I cant name one will by default. 4WD high will just give power front and rear, when you do tell it to lock up then its a true 50% by 50% power spread. with it unlocked it changes constantly for example the curved highway on ramp will make all of the wheels turn at different speeds, If one does not use their brains and has the center locked, they are damaging their vehicle and could destroy their car by loosing control, because on a high traction surface you do not need it locked and with it locked you will be over powering two wheels and underpowering the others, this is what you are talking about, well i think it is. But the true is if that happens it shows you that you dont need to be locked and in 4WD mode.
  • pschreckpschreck Member Posts: 524
    I had no idea that a Part Time system even had a center diff. I know they have a transfer case, but that's not a center diff.

     

    A Full Time system will have a center diff and a transfer case, but I've never heard of a Part Time system with a center diff. That's why it's a Part Time system is it not?

     

    Of course I certainly DO NOT claim to be a expert of any kind.
  • wwestwwest Member Posts: 10,706
    but I think even most transfer cases, at least the ones that can run unlocked in 4-hi (fulltime 4WD), have a planetary gear set which serves the same function, functionality, as the spider gears in the standard diff'l.

     

    If the vehicle can be run without the potential for mechanical damage to the driveline on high traction surfaces with both front and rear driven, it must have something between the two with the functionality of an open diff'l.
  • tlcmantlcman Member Posts: 220
    Yes the planitary gear thing is right in most cases, there are many ways to set them up and they all work, you can have a center differential that turns rear bias all the time (part time systems 2WD) then you can change the whay the drive shaftes work and an acuator will push the front shaft on to the spider gears in the differential (Part Time 4WD high unlocked) some times this might require stopping and turning one of the hub locks on the front wheel to locked, leaving the other open. I could fill a book with different ways they are set up but thats themost common that I have seen with older Toyotas and dodges ect.
  • qualitynutqualitynut Member Posts: 36
    I will agree that there are various types of 4wd systems available and that the safety and appropriateness of their use is up to the user.

     

    So many definitions out there, but I was using and agreeing with wwest on his. Part-time to me is locking front and rear for limited situations. AWD uses some sort of clutch (viscous is popular) to link together when required. My 98 Jeep Grand Cherokee (and many others) use viscous clutch that will begin to bind simply by turning the wheels and moving in a parking lot. It is a noticible effect and not the ideal situation when on slippery surfaces; that was really my point. Many AWD vehicles (Jeep Liberty, Dodge Durangos, etc.) will bind to some degree when turning tight radiuses. My point is that zero binding is ideal.

    As far as vehicles on the freeway crashing, yes, that was probably due to a locked differential (Jeep CJ-7s are common).

     

    wwest, I agree with almost everything on your Ideal AWD post, other than on slippery surfaces while slowing or stopping, I would rather not have torque applied to any wheel and allow my smart braking system to slow me down, 100% without mechanical linkage to the drive system. Torque bias to any wheels will begin to turn the vehicle in an uncontrollable fashion and then the braking system is hampered in its task. Trick years ago on rear wheel drive cars was to put into neutral while stopping on slippery surfaces and starting to spin. Car would immediately straighten out.
  • tlcmantlcman Member Posts: 220
    Im not sure that you were dissagreeing with me or that I said it any differently because I agree with what you said... maybe I worded my responses funny. Or read somthing wrong
  • wwestwwest Member Posts: 10,706
    back many years ago I can remember occassions when I applied the parking brake ever so lightly when driving (sliding??) downhill on an icy section of roadbed.
  • wwestwwest Member Posts: 10,706
    AWD perfection:

     

    Can we have an anti-lock system for/when engine braking torque is responsible for "locking" the drive wheels on an icy, very slippery surface? That would likely prevent a lot of accidents, especially for FWD vehicles.
  • qualitynutqualitynut Member Posts: 36
    Not disagreeing w/you, just trying to clarify my position which is that I feel the manufacturers are marketing technology that most people don't understand how to use (to their detriment). While I fully believe that people need to take responsiblity for their own actions, many of them are ignorant to technology and "just want to drive to their destination." Maybe I am just reinforcing my belief that the Cruiser, along with others such as Benz, Audi and others are marketing the safest (maybe as close to idiot proof you can get) 4wd vehicles available and help within reason to protect their owners from their own ignorance.

     

    Restated: I don't want to HAVE to understand when to engage or disengage the 4wd system, I just want to drive in the most efficient and safe manner. True full-time 4wd vehicles allow this without any thought. Example: My wife is truly ignorant that the vehicle has 4wd and I feel 100% comfortable that she won't do anything stupid (just don't push THAT button and lock the center differential honey, and you will be OK - alright, maybe slight concern, but hopefully you get my point).

     

    Most of my concern regards part-time 4wd (or whatever you call the technology where you don't want to drive on dry pavement due to binding).

     
    I purchased an S-10 Blazer in 1988 that had a lever that you pulled to put into 4wd. Definately was part-time and didn't want to drive curved, dry pavement with it! There are still many vehicles on the road that have this "almost useless for driving on the pavement" technology. Only off-roaders can truly appreciate this type of system. I wouldn't even want to use it on wet roads and would question its use on varying road conditions. SO, what good is it for the typical consumer?

     
    I'm getting deeper into this than I intended; sorry.
  • qualitynutqualitynut Member Posts: 36
    I wonder how the CVT systems do on this front.

     

    I can remember many times over the years when my rear-drive manual transmission car would start to turn on me when I was in too low of a gear and the engine was braking the wheel. I suppose that the phenomenon would be different in the Cruiser with better distributed potential traction, but still think that the option of NO braking in icy conditions would be beneficial.

     

    We had some pretty nasty ice/snow mix in OH last week and I was "playing" with my Avalon and was travelling on a freeway at slow speeds and simply switched the transmission from OD to 3rd gear. I could immediately feel the front begin to slow and the rear end start to come around on the icy roadway! That is what I was thinking of when I responded to your post.
  • tlcmantlcman Member Posts: 220
    Avalon is FWD right? thats what would make the back come around, or RWD would do the same too, it would slow the front wheel (FWD) and the rear would loose weight contact and loose traction, RWD would slow the rear which on ice would cause tyres to break contact and spin slower. Thats the Avalon, I would not sugest down shifting in the TLC, you can make your tyres spin slower causing the rear to swing around or other slides. Trac control will normaly not pick up on this from what I have found at lover speeds ina iced over lots. If the wheels keep moving at relativly the same speed the trac system will not notice it that mutch... (atleast in my own fun in an iced over empty bis. parking lot)
  • wwestwwest Member Posts: 10,706
    should NEVER be downshifted if one suspects a slippery roadbed. Engine braking on FWD vehicles as a result of downshifting, or even lifting the throttle completely, can result in complete loss of roadbed traction at the drive wheels which just happen to also be the way you maintain directional control of the vehicle.

     

    With experience it can be done safely with RWD vehicles since loss of directional control will not be simultaneous with loss of traction at the driven wheels.

     

    The latter is also why RWD and/or rear torque biased AWD is inherently safer, MUCH safer, on adverse roadbed conditions than FWD or front torque biased AWD.
  • serranotserranot Member Posts: 113
    I have been reading the above discussion, and it is obvious that definitions are again getting in the way.

     

    Tlcman is using "part-time" as if there is a center differential that can be either locked or unlocked. That is not my definition of a part-time system. Part-time 4wd is a front and rear driveline powered by a transfer case. There is no center differential. This is like the systems on many pickups and Jeep Wrangler.

     

    The full-time 4wd and AWD systems have some type of system to account for differing driveline speeds, be it a viscous coupling, electromagnetic clutch, center differential, or electronic diff (like Acura).

     

    So all of the above comments seem correct from a certain point of view. I agree with Qualitynut's original assertion--the average Joe is unfamiliar when he/she may properly and safely use a part-time 4wd system because of a lack of understanding of the dynamics involved. Like Tlcman has said, though, put a center diff in there and it takes away the issues.

     

    Regards,

    Tom
  • tlcmantlcman Member Posts: 220
    right thats what I was getting to... in some wierd way... RWD is actualy more dangerous on Icy roads and this is proven by Michelen and other tyre companys, reason being that if your rear steps out due to down shift, rapid accel or what ever, if it steps out the average joe driving down the freeway does not have the responses to compensate and steer into the skid, and we all know that over steer is mutch harder to control than understeer. The Front wheel drive car will loose traction at the front not stepping out but ratehr pushng the tyres (turning situation) causing understeer, which is very easy to correct for. So in that sence i dissagree with you. Its the same with buying two new tyres, your local tyre shop will recoment putting them on the fron most likly for "better steering abilitys and traction" but this is wrong and is dnagerous, put new wheels on the back of any car and the older ones on the front. The newer tyres can shed water better and will stay in contact with the road more, and if on the rear this will keep your car from over steering if you are say on a curved Highway on-ramp. Now you might understeer but that is easy to correct, so It is mutch safer in winter in a FWD car and always put your 2 new tyres on the rear. Personaly, I like RWD on Ice, people think Im crazy but I know how to control my car and its fun to get a small power slide or a bit of a drift going when turning on to an unused iced over road. Its more fun in my opinion and I have not been in a situation that I could not control yet... knock on wood..
  • wwestwwest Member Posts: 10,706
    Now tell me just how you recover from understearing/plowing in a FWD vehicle.

     

    Assume the (inexperienced) driver has sensed a bit of understear, followed their natural instincts and lifted the throttle. The roadbed was/is very slippery and the front tires had obviously lost enough traction to significantly reduce lateral control.
  • nedzelnedzel Member Posts: 787
    Just how do you do that?

     

    I've driven many rear-wheel-drive cars. Countersteering is second nature to me. I can correct for that.

     

    The only thing you can do for understeering is wait it out and hope you get some grip before you hit something...
  • tlcmantlcman Member Posts: 220
    what my sistuation that I was refering to was a twisted highway on ramp, Nedzel you are not the average driver, you have had experiance with oversteer, I have driven many sportc cars FWD, AWD and RWD I like RWD for the added fun nd involvement that is needed on slipery surfaces, lets remove the icy sisuation on our highway on ramp for this analogy, say you just put two new tyres on the front of your car and the olderones are out back, accelerating and turning say while its raining, your back end steps out, the average driver does not compute or think about this happening, so their reaction time will be longer than that of yours or mine (in my sisters case it was unexistant, resuling in the roll over) you and I would steer into the slid and have a higher chance of regaining control depending on circumastances. An enexperianced driver who reacts slower and maybe hits the brakes or guns the engine (stupid to gun in oversteer unless your steering into it with FWD car, and even then its a last resort) has a lesser chance of a full safe recovery. vehicle moving sideways with velocity could result in a roll over, or a worse acident. Now say you put those new tyres out back, and you are going around the corner same situation but your front eng pushes, most average drivers and me (dono about you) would pull a little back on the accelerator and lighten up on the steerin angle, every time ive understeered in my honda that is what I did and i regained full control in less time and in a safer manner than oversteer step out. Say if you dont regain control on an understeer or oversteer, understeer is safer because your car or SUV is not sliding sideways, thus most cars and suvs are equiped with frontal airbags and only some are equiped with side and fewer with rolling airbags, so your chance of injury is less on understeer. Im not making this up, its taught standard in driving schools in Fort Collins as my son has told me, and I have read an article that Motor Trend has writen about Michlens tyre testing directly connected with this topic I would be glad to look for a link to the story if it exist online.
  • wwestwwest Member Posts: 10,706
    ..that while there is a recovery technique for RWD overstear, most folks don't know how anyway, so it simply doesn't matter that there is NO recovery technique for understearing.

     

    Did I get that right?

     

    So I guess that means that since I do know how to recover from overstearing I'm one of the lucky ones who can continue to purchase RWD only and possibly thereby extend my life duration.
  • tlcmantlcman Member Posts: 220
    I dont think you read how I and i believe most recover from understeer, it is a recovery technique for understeer, please read it again

     

    "around the corner same situation but your front eng pushes, most average drivers and me (dono about you) would pull a little back on the accelerator and lighten up on the steerin angle, every time ive understeered in my honda that is what I did and i regained full control in less time and in a safer manner than oversteer step out."

     

    The average driver is not thinking of all of the posibilities while on the highway on ramp so when the rear starts to slide or "step out" It takes them longer to realize what is going on, thus longer to recover and less of chance of a safe recovery. Oversteer causes the backend to swing out which is very dangerous on cars and SUV's which can roll pretty easily. Few cars are equiped with rolling airbags more but still not alot have side airbags, and almost every new car has front airbags now, so an understeer where it can be corrected by lessening the steering angle and not jumping out of, but rather giving less gas to the engine. Doing this I have regained control out of every understeer that I have ever got in with a front wheel drive car. and lest say that you dont recover from the understeer or the oversteer example. Not recovering from an over steer, means that your car/ SUV is sliding sideways, and if its an SUV can roll pretty easily, causing a more severe accident, if you cant regain control on a understeer, then you will hit somting from the front and most cars are designed to take frontal impact, and many have multi stage airbags, its safer than rolling your car, plus if you cant regane control and happen to go off the road, and there are no obsticals then you can still control your car as you play around in the mud trying to come to a stop. Do you understand me now?
  • russlarussla Member Posts: 74
    in my personal experience,

    it seems the natural response when something wrong happens, is to let up on the throttle,

     

    in an oversteer situation, this helps the car regain composure, as the rears stop spinning (from applied power) and regain traction and fall back in line.

     

    in an understeer situation,when accellerating around a corner, in some front wheel drive cars, letting off on the throttle, very often transfers weight back to the front wheels, giving them add'l traction, and at the same time unweighting the rear, which causes an oversteer situation.

     

    regards
  • tlcmantlcman Member Posts: 220
    Ive never seen oversteer resulting from corrected understeer, I see what you are saying but when you let up on the throttle you let it regane traction because when you are turning the front wheels already have a strain on them to move the car in that certain direction, when you want to accelerate and turn at the same time you put two forces on the tyre; directional changes, and acceleration. The combination of these and the ammount is what starts understeer, the tyres can not keep traction with the steering angle and the amount of torque that is being put to them, not transfering of weight.
  • neumie2000neumie2000 Member Posts: 133
    Hello everyone. I'm sure this question has already been answered in this forum, but I was unable to locate the answer during my brief search. I purchased the V8 4Runner SR5. I know that the V8 is in 4WD all the time; however, my question is whether the 4WD system on the V8 4Runner is still the same as the V6, just without the option of dis-engaging the 4WD. I know several other vehicles (like the Honda CR-V) are "all wheel drive all the time," but I know this means that only two wheels actually drive the vehicle until some slippage is detected and torque is transferred. I am hoping that the 4Runner is still a true 4WD vehicle, meaning that all four wheels are always engaged and driving the vehicle. Is my hope correct? Thanks in advance for any help.
  • tlcmantlcman Member Posts: 220
    correct, there is a center differential that you can lock, spliting power 50/50 but otherwise under normal driving yes all wheels are powered equaly.
  • canddmeyercanddmeyer Member Posts: 410
    Any of you 4Runner aficionado's know the crawl ratio of a 2003 V6 4Runner 4WD...thanks

     

    Crawl ratio = rear end gear ratio X lowspeed transfer case gear ratio X 1st gear tranny gear ratio.

     

    P.S. I've always favored Toy's & Chevy's for this reason...never got them stuck like I got my Fords stuck & stuck & stuck...you get the idea.
  • tlcmantlcman Member Posts: 220
    stats are on toyotas specs sheet under 4Runner vehicle here

     

    http://www.toyota.com

     

    -Mike
  • wwestwwest Member Posts: 10,706
    Isn't the "new" 4runner's AWD system rear biased, 30/70 F/R, or does it go from 50/50 to 30/70 as lateral forces build (more need to dedicate front traction to directional control), as the literature seems to imply??

     

    And lifting the throttle for recovering from understear or plowing in a FWD vehicle does not always, or maybe even rarely, result in recovery.

     

    Cadillac actually installed an over-running clutch in their FWD vehicles with the high HP/Torque Northstar engine to help prevent loss of control resulting from your recommended recovery procedure.

     

    In many FWD vehicles lifting the throttle will oftentimes result in enough engine drag torque to the front wheels that when "added" to the lateral forces from stearing will still exceed the front tires' traction coefficient.

     

    I am extremely partial to vehicles that allocate the front tire contact patches to directional control and the rear to drive and drag.
  • tlcmantlcman Member Posts: 220
    which 4 Runner are you talking about V8 or V6

     

    and secondly

     

    when you want to accelerate and turn at the same time you put two forces on the tyre; directional changes, and acceleration. The combination of these and the ammount is what starts understeer, the tyres can not keep traction with the steering angle and the amount of torque that is being put to them. These two reasons are why the tyres break loose, so if you correct them, then you will correct the probblem, thats too simplistic but i could write a page on it if you would like.

     

    "over-running clutch"

     

    Im assuming this means that the changing of gears is mutch more smooth, this means that like the word implies, the clutch mechanism gives mroe slip so that there is less force applied to the front tyres right away which could cause them to break loose, and on a car not equiped witha over-running clutch you would correct that by lifting the throttle like I said.
  • wwestwwest Member Posts: 10,706
    Prevents the engine from being "driven" by the tires' roadbed traction. No engine braking, drag torque, fewer incidents of crashing due to loss of control on a curving downhill icy run.

     

    Get off the gas fully, front tire traction fully dedicated to maintaining directional control.
  • tlcmantlcman Member Posts: 220
    in the car equiped with that device yes you should but others without it, you would not want to jump out of the gas because you would put againa decel. force on the tyres. stay in the gas just with the right amount of foot and you will keep the tyres moving the speed of the ground. I've never driven a car with an over running clutch, so i can only go by what you say.
  • wwestwwest Member Posts: 10,706
    learning to feather the throttle, finding the sweet spot, such that the engine is neither driving nor dragging, is somehow easier to accomplish than learning to stear into the skid in a RWD vehicle?

     

    NOT!

     

    Just as the AAA is now suggesting for recovery from understearing FWD vehicles, slipping the transmission into neutral is somewhat cumbersome but will always work.
  • tlcmantlcman Member Posts: 220
    again that suport what I said... i dont think that you understood me. Understeer is easier to control, that also means that if you cant recover you can still have general control, oversteer if you cant regain control you can roll it or throw your pasenger or you into a light pole center divide, or what ever else might be aorund, Let up on the throttle slip it to and puting it in N is basicly the same you let the wheels keep their speed with the road, if you jump out of it and you car does not come with a ""overrunning clutch" then you are putting an engine break force on the tyres and defeating the purpous, N or less gas will work. Been driving for 35 years and half of my cars have been front wheel drive, born and raised in Colorado and have experianced my share of over and understeer, thank you. There is no sweet spot, infact its a pretty large area, You dont need a flight calculator by your side to calculate the throttle imput, All you need to do is not floor the throttle, or jump out of it, just let of a bit and decrease the steering angle, no calculators needed... Im sure you wanted to use one though.
  • pschreckpschreck Member Posts: 524
    Since when? AWD implies that the 4Runner doesn't have a two speed transfer case like a Subaru. The new 4Runner is Full-Time 4WD by my understanding.

     

    You guys need to get your terms straight or you're going to confuse people that are reading this forum for the first time and have little knowledge of these systems.
  • steverstever Guest Posts: 52,454
    Unfortunately even the manufacturers don't seem to be consistent with the terminology. I would hope that Toyota is consistent within its model lines though. Cliffy has a good summary in the first dozen posts or so.

     

    Steve, Host
  • wwestwwest Member Posts: 10,706
    Is simply an add-on to 4WD capability. Other than being a common "accessory" to many 4WD systems (and virtually ALL of the older ones), having a 2-speed transfer case does not relate in any way to AWD or 4WD.
  • pschreckpschreck Member Posts: 524
    Then what IS the difference between AWD and 4WD?

     

    I believe that a CENTER DIFFERENTIAL is an accessory to a 4WD system while a TRANSFER CASE is fundamental to a 4WD system.

     

    AWD never (that I know of) has a TRANSFER CASE.
  • wwestwwest Member Posts: 10,706
    except for marketing differentiation...

     

    AWD systems are presumed to be FULLTIME, but many 4WD systems were, and are, fulltime. I think the "marketeers" wanted to differentiate AWD for 4WD for good reason. AWD is generally taken to mean fulltime 4WD with no driver intervention.

     

    Most traditional 4WD systems, even those with fulltime mode, have other drive modes, thereby require driver intervention.

     

    The new 4runner, for instance, has a RWD mode, an AWD/4WD mode, and a part-time 4WD mode wherein the center differtial is locked.

     

    Disregarding its off-road capability entirely, the 4runner's fulltime system is likely one of the best in the market today.

     

    Oh, sorry, almost forgot. Most transfer cases also have a differential in the form of a planetary gear set. I think, not sure, the term "transfer case" has come to mean a 2 speed gearbox, by default.
  • 4wd_newbie4wd_newbie Member Posts: 5
    Am putting together spec's for the '05 Tacoma we want to purchase(4WD, Auto., Off-Road #2, Impulse Pearl, Running Boards(RB), Bed Mat(CJ), JBL Stereo(EJ)...). Edmunds, and KBB list the below option:

     

    VEVSC w/DAC

    Includes Vehicle Stability Control (VSC) with Traction Control (TRAC), automatic limited slip differential, hill-start assist control (HAC) and downhill assist control (DAC). REQUIRES OG or PT or SJ or SN.

    But this is not listed as an option on the buyatoyota site. Does anyone have this option? Is this NOT an option with the vehicle I have described? I'll be doing in-town, occasional snow/ice, and some beach driving - is this package worth $800?
  • stove1stove1 Member Posts: 53
    It might help a little but I doubt it makes too much difference on snow and ice when you don't have traction. VSC operates by selective braking one of the wheels . What good that will do when you don't have traction on ice ?
  • hank14hank14 Member Posts: 133
    This thread and others like it should have a mandatory warning label that anyone who reads it should be prepared to become dazed and confused. If someone misuses their vehicle- from tire inflation to fluid type to how to use it's respective 4WD system, it's their own fault. Read your manual. Take a 4wd class. Practice in an empty parking lot, off road, or something. No wonder everyone is so confused. I only keep reading because it is comical. I think I'll stick to a Landcruiser specific forum from now on. Happy New Year.
  • wwestwwest Member Posts: 10,706
    The only time I can say for sure that my VSC kicked in was when I drove a bit too agressively through a water puddle as I turned left out of a driveway. Obviously the same thing could happen on a rain slicked street or even an oily spot.

     

    No ice or snow required.
  • buffalonickelbuffalonickel Member Posts: 113
    This discussion thread is like reading a script for Abbott and Costello's Who's on First!

     

    B
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