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Toyota 4WD systems explained

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Comments

  • llofgrenllofgren Member Posts: 129
    Thanks for the input! Yes, I did see that pic of the RX 300.
    I still don't quite get it though. Here is the explanation by Cliffy:

    "Highlander and RAV4 by cliffy1 May 16, 2001 (04:01 pm)
    These utilize a limited slip center differential and open front and rear differentials. It is a viscous coupling center differential. If one of the front wheels begins to spin faster than the rear, the heavy liquid in the center begins to firm up which routes more power to the rear. Once torque is equalized, the 50-50 power split is resumed. This system is always engaged and requires no driver input.

    It is possible to become stuck with this system. This is because of the open front and rear differentials. If both right tires were on ice, all power would be routed to these wheels."

    In the RX 300 situation (picture), the front wheels are slipping, so why doesn't the viscous coupling in the limited slip center diff kick in to power the rear wheels and send the SUV up the ramp? It (the center diff) does kick in under high torque transfer conditons while normally driving to split the power 50/50 front and rear. Starting from a stop on dry pavement is a high torque low speed transfer....why does IT work and the boat ramp thing fails? And what if I am parked with my front wheels on solid ice and my rear wheels on dry pavemnet on a slight upslope? It would seem to me that the limited slip center diff would engage the rear wheels to push the vehicle out. What am I missing here?

    You said that the center diff routes power to the least resistance....but isn't that the direct opposite of what everyone (else) says it does?
    That is, the slipping wheels transfer power to the viscous coupling which then powers the NON slipping (higher resistance) wheels(s).
  • drew_drew_ Member Posts: 3,382
    Remember the word "limited slip". This means that it has a certain limit, and is by no means a locking differential. As such, up to a certain limit will transfer the torque to the opposite driveshaft as required. However, once that limit is exceeded, the differential will act like a conventional open differential and send power to the path of least resistance. This is why off-roaders insist on mechanically locking centre and rear differentials, not the limited slip variety. This way, the wheels are mechanically bound to spin at the same rate and power won't be lost like it will with a LSD.

    The Lexus fails the roller test (representing snow or ice on the road) because when the front wheels slip on ice the unmanaged center differential allows all torque to get lost at the front wheels (path of least resistance) rather than making any torque available to the rear wheels. Since the RX has an open front differential, even if one front wheel doesn't have traction, all of the power will leak out to that wheel. I remember one owner complaining about his '99 RX getting stuck in a ski resort parking lot, with only one front wheel spinning and the rest stationary. All of the power was being leaked out to that wheel only.

    This is the reason why Lexus finally added stability control and traction control for the newer models. To help to combat this problem.
  • llofgrenllofgren Member Posts: 129
    I am getting it a little, I think. So why have I never noticed this problem before? I regularly drive my wife's '92 AWD Sub Legacy Wagon and have nave never gotten stuck in it, except once, when ground clearance did me in after 15" of snow. Otherwise it has gotten me through some pretty extreme winter conditions, on remote Minnesota roads.
    What about the Honda RT 4WD setup? Would that do better on the "ramp roller" test since the clutch pack would probably slip less than a viscous coupling?
    How does the Escape/Tribute system allow a continuous AWD system to be locked?
    Lastly, what determines "the limit" to which a limited slip viscous coupling will transfer power to the other axle (as opposed to letting it leak out the path of least resistance)?
    (sorry for all the questions)
    Les
  • cliffy1cliffy1 Member Posts: 3,581
    Your Subaru, like most other vehicles will never see a roller ramp and that is why you have never experienced something like this. That little demonstration was put on my Mercedes engineers for sales training. Those demonstrations are always set up to make the competition look as bad as possible. Toyota does these all the time as well, sans the pictures on the Internet.

    Drew is correct about the limited slip center, but the chances of ever experiencing something as drastic as rollers on an incline are very remote. I have my doubts that ice could have the same impact. I played with this system last winter and was unable to duplicate the same effect. There was always enough traction to get moving, even on sheet ice.
  • llofgrenllofgren Member Posts: 129
    Thanks for the reassurance (my HL is "on order"). It supports my subjective sense that this (AWD) system is a good one but it was unsettling to see that roller ramp picture with the RX 300.
    I enjoyed reading your posts from this winter on the Highlander! I saw where the snow had shut down D.C. and you took the two AWD HL's (one with VSC and the other without) to the snow and floored them:)
    I am eagerly awaiting my HL!
    Les
  • eagle63eagle63 Member Posts: 599
    I've posted this question in another forum on edmunds with mixed answers. How does the rear-diff lock on the tacoma work? People have told me that you must be in 4-lo to engage it, others say it can engage anytime you press the button. Also, is there a speed limitation on the locker? -meaning, do you have to be going under a certain speed for it to work? thanks in advance!
  • cliffy1cliffy1 Member Posts: 3,581
    Until the PreRunner came out, I thought I knew the answer to this question. The training I went through told us you had to be in "low" before engaging the rear differential lock. I had assumed that this was a mechanical requirement. Since the PreRunner can also have the locker but has no low gear range, I now think this is more a suggestion than a requirement.

    I also know that there is no speed limiter. The warning label in the cab does tell you to keep it under 5MPH but I don't think you are restricted to this.

    Because my store isn't near any dirt roads, I just have not had opportunity to experiment with this.
  • eagle63eagle63 Member Posts: 599
    thanks for the response. I've talked to a handful of toyota dealers in my city and I got a different answer each time. (one of them didn't even know the difference between the Xtracab and the doublecab!) some told me you had to be in 4lo, others said 4hi or 4lo, and one said anything - it doesn't matter. But you bring up a good point about the prerunner. obviously if the prerunner has it, you can engage it in 2wd.
    hopfully I can test it on my next testdrive. thanks again!
  • vivian3vivian3 Member Posts: 8
    Thanks for the helpful explanation of 4WD systems. I live in Alabama, and I am looking to buy a Highlander. I am deciding between FWD and AWD. Either way I would get Traction control and VSC. We rarely get snow or ice here. And although I read your site reference to the advantages of 4WD on dry payment, I am a very conservative driver. I have never skidded a FWD or AWD vehicle on dry pavement (although I've done some spectacular skids in cold weather in Canada). Also, I am concerned that the additional weight of the AWD system will increase braking distance and hurt fuel economy. However, we do get heavy rain here. What advantage does a 4WD system give in heavy rain? Will it make the vehicle less likely to hydroplane, or will it just increase traction when making turns and sudden changes? Thanks!
  • cliffy1cliffy1 Member Posts: 3,581
    AWD will give some advantage in rain, but I don't think hydro planing will be affected. You will get better traction and handling. There really isn't much extra weight on the HL AWD system so I don't think braking distance will be affected much but gas mileage drops a little.

    One other thing to consider is resale. I really don't know the SUV market in AL, but in general, the AWD version will do much better down the road.

    I hope this helps. I don't think you can go seriously wrong either way.
  • hicairahicaira Member Posts: 276
    Maybe you can help me here but I am wondering if the transfer case on my Land Cruiser (98) is working correctly.

    A couple of weeks back I was decending a very steep road (in the White Mtns., CA). Due to the grade, I wanted to use engine braking and so I stopped the car, shifted it to Neutral, shifted the Transfer case to "low", and then shifted the gear selector to first. Started off and the car seemed to still be in "high". So, I applied the brakes to a near stop and the TC finally kicked into "low". All fine and well I assume. As I was going down the hill we saw a herd of Bighorn sheep. Wanted to take some pictures so I came to a stop, put it in park and set the brake. The TC was left in "low" When we resumed the decent I again noticed that the car was in "high". Again, I applied the brakes to a near stop and the TC automatically shifted to "low" - just as before. Just to test, I did the whole thing again (lower where the road was less steep) and got the same results.

    So, why was the TC automatically shifting itself to "high". Neither of my prior 4wd Toyota's did this. When they were in "low" they stayed there. Does the fact that it is an auto tranny make it want to try to outsmart me? A dealer service advisor seemed flumoxed by my question so I have to wait for my regular guy to get back from vacation to ask again. In the meantime, you have any ideas?

    Thanks,

    HiC
  • toadmantoadman Member Posts: 39
    I read the informative explanations regarding the different Toyota 4WD systems and have a question regarding the Tacoma High 4 Selctor switch.

    I recently test drove a Tacoma Double Cab 4WD. The sales rep was new and it was just his 4th day on the job. I asked if there was any restrictions on engaging the High 4 slector. He said he wasn't sure. He then pushed the selector switch while we were on the test drive and at a speed of around 40 MPH on dry pavement. There was a slight jerking as if we had just hit the O/D button.

    Reading an earlier post it was mentioned that on dry pavement it should not be engaged over 50 MPH, if I remember correctly. Could this have damaged the transfer case or drive shaft or caused any other damage to the 4WD system? Seems kind of irresponsible to have engaged the High 4 Switch if the sales rep wasn't sure what might happen.
  • obrien30obrien30 Member Posts: 2
    have a 92 toyota surf(4runner) 3L V6 auto 90000k (56000 mls)imported from japan. why were we told to reverse 6metres (20 feet) after changing back to 2wd?
    we had dreamed about having a surf and test drove about 10 over 18 months, but it wasn't untill we purchased one that the dealer told us about this rule/trick? are we the butt of a joke? Great site!
  • cliffy1cliffy1 Member Posts: 3,581
    I've been away from the boards for a few days so I'll answer each of these. First to HiC. I too am flummoxed over this one. I have absolutely no idea why it would revert to the high gear range under the conditions you describe. It does sound like it is by design because of how repeatable it is. I would have your local dealership look into this to make sure.

    Toadman. The selector will not engage until you drop below 50 (or 62 if it is a push button option) but once engaged, you can drive at whatever speed you wish. The danger of using it on dry pavement relates to turning corners and since you described no problems there, I'll assume it is OK. It sounds like you have an ill-informed salesman, but under the conditions you describe, I doubt there was any harm done.

    Obrien. Back in the olden days, you did have to reverse 4WD vehicles to disengage the system. The 92 Runner had an "Automatic Disconnecting Differential" which means you don't have to do this. Your salesman was probably "old school" and made an honest mistake.
  • drew_drew_ Member Posts: 3,382
    Regarding the reversing, it was to disengage the automatic locking hubs. Many mid-'90s SUVs with auto locking front hubs still required this for the hubs to be disengaged completely. I seem to recall that the '92 4Runner did have auto hubs though!


    Drew
    Host
    Vans, SUVs, and Aftermarket & Accessories message boards
  • cliffy1cliffy1 Member Posts: 3,581
    While the 92 did have what many called "auto locking hubs", it was actually an automatic disengaging differential which did not require one to back up to disengage. At the time, most of the domestic manufacturers has auto hubs that did require backing up. This was probably the source of his salesman's confusion and misinformation.
  • drew_drew_ Member Posts: 3,382
    Yeah, the Ford Explorer was an example of this. A friend of mine had a '96 Isuzu Rodeo which did recommend backing up for several feet to disengage the auto locking hubs though. He never did and the truck still ran fine when he sold it. :-)
  • hicairahicaira Member Posts: 276
    As cliffy said, ADD was standard on this truck. I recall that when I bought mine the brochure touted the ADD as a "new" improvement.

    If I read correclty though, Obrien's 4Runner (Surf) was not a US import, but an AUS/N.Z import? It is possible that the ADD was not offered, or only offered as an option in that region. Quick question: does it have a live front axle or IFS?

    Cliffy, I'll be driving my LC with one of the better service reps at my next service visit. Funky thing is that I have done some steep hill decents before and do not recall it auto shifting the TC. I'll let you know what I find out (in another month or so).

    HiC
  • obrien30obrien30 Member Posts: 2
    the 4runner is ADD. what is IFS?
    Japan exports some 90 000 cars a year. at one stage New Zealand was importing 75% of them!!
    Check www.toyota.co.nz and look at "Signature Class" may also like to look at new cars/trucks as well -prices will amaze you guys.
    naturally these imports have killed off car assembly here - Aussie still has the major car companies producing cars etc.
    Also, these imported cars/trucks have warnings/instructions written in Japanese!!
  • hicairahicaira Member Posts: 276
    IFS: Independent Front Suspension

    Toyota makes available in Aus/N.Z multiple versions of vehicles that are simply not imported to the states.

    The fact is, your market generally takes off-roading a bit more seriously than than the US market. The Land Cruiser is a typical example.

    In the US we have one version: the 100 series with the V8 gas engine - all fully loaded with leather, sun roofs, etc.

    In Oz, you have: 100 series: 3 engine choices (inc. a diesel), IFS or solid live axle (not on the V8), one or two petrol tanks, and all the "standard" stuff here are really options there. You also have thr 90 series with the same array of configurations including two wheel bases. All in all, 9 distinctive Land Cruiser choices compared to our 1.

    Anyway, I would guess that in 1992, while in the US we had two choices (2wd or 4wd) and two engines (v6 or I4), all used the same chassis set up which included IFS. I am almost sure you had the option of a live axle front set up (same as on the pick-ups prior to 1989 here).

    Finally, if you do have ADD, then you do not need to back up to disengage 4wd but it does take a least one full wheel rotation (forward or reverse) to disengage the auto locks.

    enjoy,

    HiC
  • cliffy1cliffy1 Member Posts: 3,581
    I've been out with an ankle injury and have not been able to access this site much recently. I appreciate your input here. You have more technical knowledge than I in many respects.
  • abc246abc246 Member Posts: 305
    I bet your friend backed up sometimes during the time he had the SUV!
  • drew_drew_ Member Posts: 3,382
    Heh, no I mean backed up right after the transfer case was switched back from 4WD to 2WD to disengage the auto locking hubs.


    Drew
    Host
    Vans, SUVs, and Aftermarket & Accessories message boards
  • wkckwkck Member Posts: 2
    Hi, Cliffy
    Can VSC and TRAC be added to a 2000 4Runner Limited 4x4 equiped with rear locking diffrential? If yes, is it worth?
    I do some off roading, but not serious. I'm thinking of adding these two safety features for my wife driving the vehicle.
    Thanks!
  • cliffy1cliffy1 Member Posts: 3,581
    Sorry, but no it can not be retro fitted. Well, if you throw enough money at anything, you can get it to work, but it would not be cost effective. The VSC/TRACS is an integrated part of the vehicle. If this is really important to you, you are better off trading in for a 2002.

    FYI, if you live in the Central Atlantic Region, there is currently a $1000 rebate or 0% financing on the 2002 Runners.
  • wwestwwest Member Posts: 10,706
    Assuming the HL AWD is the same as the RX AWD, I'm setting here looking at the 2000 RX300 AWD shop manual. The RX300 has three open differentials and ONE viscous clutch from one output of the center differential to the rear drive shaft. I think with this arrangement the torque to the rear can NEVER exceed 50% (nominal might be as low as 5%) and with three open differentials the only thing that keeps it from being a OWD (one-wheel-drive) is TRAC, and that only exists on the 2001 model. LSD was available on 99 and 00 models.
  • loma1loma1 Member Posts: 32
    I recently purchased a new 4Runner and took it off-road about a week ago. Something I noticed was that even with the center differential locked traction control was still engaged. From what I knew about this system I didn't think it would be. Later when looking through the manual, and taking the dash light at face value, it would seem as though only the vehicle skid control is turned off, and the traction control remains on, diff locked or no.

    Gary
  • cliffy1cliffy1 Member Posts: 3,581
    I'm curious about your experience and have a couple of questions. First, are you positive the center differential was locked? Was the amber light lit solid when you were driving? I only ask this because if you don't engage this in the correct order, the light will be flashing and therefore, not engaged. The correct order to lock the center differential is to first engage the regular 4WD system and make sure it is fully engaged first. Then, while stopped, hit the center diff lock button on the left side of your dash.

    The next question I have is to ask how you know the TRACS system was still operational. Was the indicator light flashing and did you hear the ABS clicking?

    I am only asking this because I am curious. I'm not doubting you but I want to make sure I understand the conditions you were in. I would actually be happy to hear the TRACS works with the center locked as it would keep correct power left to right, but your description goes against my experiences and what I have been able to glean from the technical folks at Toyota.
  • loma1loma1 Member Posts: 32
    I was in a couple of different situations, both involving the low side of the transfer case. When you push the xfer case lever forward you will automatically go into 4wd open diff even if you were in 2wd to begin with. The first time I noticed it was a couple of days after I had gotten the truck I attempted a short climb at a fairly steep angle, it wouldn't go with the diff unlocked so I pushed the CDL button. I waited until the CDL amber light came on, putting the transmission in neutral helps this happen faster, and then made another attempt and I heard the TRACS system engaging and I might have seen the indicator come on, don't remember.

    The second time was about a week ago and I was climbing some ledges, once again in low, and was not able to get the rear wheels over the first ledge. I had decided the CDL wasn't very pertinent since the trac was on either way what would it matter? I wasn't getting up so I tried the CDL again, waited till the light came on, tried again and it pulled right up. Even after using the CDL switch I could still hear the tracs system engaging. I think I remember the trac indicator come on but I'm not sure.

    Looking at page 122 in the owners manual it says that the VSC uses traction control to prevent skidding and that the CDL button will turn VSC off, but it doesn't say that TRACS is turned off.

    I'm more than happy with my 4Runner. It's behavior is different than expected, but if the TRACS system is supposed to engage with the CDL, more power to me.

    Gary
  • wwestwwest Member Posts: 10,706
    If I understand Lexus very confusing response to my question on this matter, Trac is used left to right or right to left, not front to rear or vice versa. Now you don't need LSD front or rear, Trac takes its place. Not any real reason for it to be active unless the center diff. is locked.
  • kmhkmh Member Posts: 143
    Cliffy,

    I've got an '99 RX300 AWD but does not appear to have a limited slip differential. Could you please tell me what the differences (perceived or actual) are with and without the LSD? Thank you.
  • cliffy1cliffy1 Member Posts: 3,581
    On the '99 RX, the rear differential is "open" rather than limited slip, unless you got the option of the LSD. For all practical purposes, I don't think you'll notice much difference. If one of your rear wheels begins to slip, more power should move to the front axle. If you have the LSD, power would also be biased to the side with more traction. Because you have an AWD, your front axle should be able to compensate for the lack of rear traction in most situations.
  • kmhkmh Member Posts: 143
    First, many thanks for your reply. Your knowledge and helpfulness is appreciated!

    Now, I believe I understand what you posted. So, if the front wheels slip then will the power be diverted to to the rear wheels? If so, how much power percentage-wise? And since my RX doesn't have the LSD, then will power be distributed evenly to both wheels?

    Thanks again for all your help!
  • cliffy1cliffy1 Member Posts: 3,581
    I don't know the percentages other than when all wheels have equal traction. In this situation, it is an even 50-50 split.

    With as much as I have been able to learn, I am still a bit shaky on the LSD, both center and rear. I believe it is possible to exceed its ability to divert power perfectly. In theory, if the front axles are on sheet ice, most of the power would go to the rear. Once there, it would be split by an open differential that would bias power to the side with the least traction unless both had equal traction in which case you would have a 50-50 split.

    I hope this helps. Drew, the host, may be able to add some insight here.
  • tidestertidester Member Posts: 10,059
    Viscosity of some motor oils does decrease with temperature! The trick is to add just the right polymers to the oil so that they become non-Newtonian fluid which is just a fancy way of saying the viscosity goes down as the temperature goes up.


    Of course, if you make the oil too hot, the viscosity reverts to its "natural" behavior and falls like a rock. Then you're in serious trouble.


    Here's an article you might find interesting.


    tidester

    Host

    SUVs

  • cliffy1cliffy1 Member Posts: 3,581
    Ummmm.... The viscous coupling center differential has always been of the limited slip type. The center differential has always been of this type.
  • wwestwwest Member Posts: 10,706
    My 2000 AWD RX300 shop manual (have 2001 on order) clearly shows one output from the center "open" differential driving the front "open" differential and the other output from the center differential driving the input to a viscous clutch, the output of this clutch goes to the rear driveline.

    Maybe the 2001 is different, I don't think so, but will soon know the truth.
  • mhoff36100mhoff36100 Member Posts: 2
    Greatings! Thanks for all the useful information ...

    I am replace my '92 Ford Explorer (4WD w/LSD rear axle) and am looking at '01 4WD 4Runners. My main off-road use would be on beach sand. Question is, would normal 4WD mode work fine (with the traction control keeping things going if one wheel lost traction), or what are the circumstances were it would be desirable to lock the center diff?? If this does turn the traction control off, then it seems as if the open front and rear axles could create a problem...

    Anyone have experience with a 01 or 02 4Runner on sand?

    Thanks!
    Mark
  • cliffy1cliffy1 Member Posts: 3,581
    When in 4WD, the rev limiting "feature" is not enabled so you may be able to get away without locking the center differential. You would still have the braking action and this may kill your momentum and the center lock is the only way to defeat this.

    Open diffs on sand is not the killer you may think it is. Take a look at the other vehicles out there and you will see plenty of Toyota trucks doing just fine and every one has this arrangement.
  • loma1loma1 Member Posts: 32
    If you are concerned about traction control being turned off when in 4wd, it has so far been my experience that locking the center diff on my 01 doesn't turn off the traction control.

    As for when you would need to lock the center diff I've found myself a couple of times in a cross-axle position where three of wheels have traction, but one has so little traction(nearly off the ground)that all power escapes to that wheel, even with the traction control. When I locked the center diff it forced the front to turn as well and it pulled on out.

    I've not had my 4runner on the sand but from what I've heard about traction control in the sand, it can hurt you on hill climbs where it impedes your forward movement.


    Try this bbs for more info. http://www.outdoorwire.com/cgi-bin/ultimatebb.cgi?ubb=forum&f=13


    Gary

  • brando69brando69 Member Posts: 47
    I have decided that I will be purchasing a Sequoia SR5 in the next few weeks or sooner.The only problem is deciding if I should spend the extra $$$ for the 4WD version.

    I do plan to travel to the mountains during the snow season with the wife and kids. I also plan doing some light off roading to go fishing and or hunting.

    The driving to the mountains and the light off roading can be easily handled by a 2WD but it would be nice to have the 4WD just in case. I used to have a Land Cruiser(got stolen) and that beast would go anywhere I wanted it to go.

    The Sequoia is just bigger, and roomier than the LC and wonder if I buy the SEQ 4x4 would it be just as good as my old Land Cruiser.

    I plan to keep this vehicle until it dies or I do. :) Any advice would be appreciated. Thanks.
  • cliffy1cliffy1 Member Posts: 3,581
    The Sequoia 4x4 will be better than your old LC unless the LC was a 2000 or newer. I realize that 2 wheel drive will handle most of what you want, I also know the peace of mind of knowing that you can push it is you need to. Since you're a long term owner, spend the extra money. In 7 or 8 years, you will not notice the difference in your bank account. If you get the 4x2, you'll always wonder if you made the right decision.
  • brando69brando69 Member Posts: 47
    Thanks for the infomation Cliff. Maybe you can answer my next question. What makes the Sequoia 4x4 of today better than a Land Cruiser 4x4 made before 2000?

    Is the Sequoia 4x4 better, the same or just behind a LC 4x4 made from 2000 and newer?

    Any information or articles on the Sequoia's offroad performance? I know that the LC is the benchmark for all other 4x4's.

    Thanks for any information.
  • cliffy1cliffy1 Member Posts: 3,581
    The pre-2000 LC had a limited slip center differential while the new ones have the open differential with the traction control to govern power shifts. The pre-2000 did have one advantage though in that you could lock the center and rear differentials (pre-98's could lock the front as well). You would have to be doing something pretty extreme for that to be engaged though.

    The only advantage the Sequoia has over the new LC is the ability to place it in 2WD if you wish. Other than that, they are the same.

    As for off road performance, the LC may still get the nod due to a shorter wheel base and more robust front suspension. There was a TH member who posted a long and detailed description of his Sequoia's off road adventures. His user ID was slickrock. He posted it several months ago and it would take a lot of back tracking in the Sequoia topic to find it. He was VERY enthusiastic about its performance.
  • stopmakingsensstopmakingsens Member Posts: 3
    OK…I THINK I understand…I have spent WAY too much time trying to figure this stuff out.

    I bought a 2001 Sequoia Limited in March 2001. (20K miles so far - Mexico, Canada, California)
    I think I understand the following:

    This is a "Full time 4wd" which means it has a high and low set of gears, but also has a 2wd mode.

    3 open differentials (front/rear/center)
    Open differentials are reliable and relatively simple.
    In 2wd mode the rear wheels are doing the pushing.
    In 2wd mode if one of the rear wheels slip then all power goes to that spinning wheel BUT the computer applies the brake to that wheel to simulate a locked or limited slip differential (TRAC). In addition the engine is limited in RPM which can be annoying / dangerous depending on where you are, what you are trying to do, etc.
    In addition variable skid control (VSC) is active keeping you from doing doughnuts in the parking lot.

    In 4wd mode the TRAC braking is still active (to simulate locked or limited slip differential) but the engine is not limited in power or RPM, and VSC is still on. Because the TRAC engine rev limit is removed and the fact that 4 wheels are being driven, this is almost the preferred mode to be in, especially in anything than less than ideal conditions.

    4wd has 2 modes - low and high. High is "fine for almost anything"…

    4wd low - with more torque going to the wheels - if you are in deep mud/snow/etc.

    Question 1) Wouldn't 4wd low just get you into deeper trouble if you are stuck?
    I am originally from the Midwest and the only time I can imagine using it is if there was a snow blade on the front of it and you want to push some snow…any other situation?

    4wd Locked - locks center differential so equal power goes to front and back (makes it into a transfer case). This is the only mode in which the TRAC braking is disabled. VSC is also off. Guaranteed to get equal power to front and back. But with the open differentials in the front and back it is POSSIBLE that if a wheel in the front is spinning, AND a wheel in the back is spinning, then all power will be to those spinning wheels and you are not moving. In fact keeping the 4wd unlocked may be preferred depending on which wheel(s) do not have traction.

    In fact - assuming 4wd Locked would (presumably) only be used in extreme circumstances (at least some of the tires in the air). Then it would actually make the Sequoia into a front wheel drive if a rear wheel were spinning and a rear wheel drive if a front wheel was spinning.

    I have noticed that it is possible to change the differential to an after market Locked differential if that was desired.

    Question - would 4wd high be the first choice for a wet / slippery boat ramp? This would have lower torque to the wheels and hopefully not spin the tires as easily. If more torque was needed then 4wd low could be used(?)

    If my understanding of the Sequioa is incorrect let me know, I really want to understand...

    Thanks in advance!

    Dean
  • cliffy1cliffy1 Member Posts: 3,581
    Perfect summary and perfect comprehension of the systems. I couldn't have said it better myself.

    As to your question of when to use the low gear range, it really would take something fairly extreme. Pulling another car out of a ditch, extricating yourself from a snow bank or a real problem at a boat ramp (such as a short steep ramp and your trailer tires dropped off the end) are about the only situations that the low gear range may need to be employed. I know you can imagine others scenarios, but you get the picture.

    I can see little use for the center lock mode myself. About the only thing I can imagine is if you want to drift and slide in corners on dirt.
  • gpm5gpm5 Member Posts: 785
    Definitely go with the 4x4. I have a SR5 sequoia 4x4 and we keep it in 4x4 mode essentially all the time. The gas mileage on the hgy at 65-70 mph is ~20 mpg (give or take 0.1 to 0.2). The stability on the hgy is improved in 4x4 mode. I notice better handling on bumpy highways (almost all highways now-a-days) in 4x4 mode even at high speeds, possibly because a rear wheel can bounce, and torque is transferred to the front.
  • brando69brando69 Member Posts: 47
    Thanks for the advice and information. I have decided that I'll be buying a Seq.SR5 4x4 in the next few days and have my eye on a red one I saw a few days ago.
  • dididadidida Member Posts: 4
    I am going to buy a 96 4 Runner this weekend and I am not sure if the 4WD system is working. Anyone have ideas to tell? Thanks.
  • wwestwwest Member Posts: 10,706
    If its a part-time system, should only be used on low traction surfaces, you can put it into this mode, drive VERY carefully and slowly on a high traction surface in an ever tightening circle.

    The steering wheel will kick back at you and you will hear the driveline windup and the tires scrubbing more and more as you tighten the circle.

    Don't have any body parts, fingers, inside or through the steering wheel.
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