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Toyota 4WD systems explained

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Comments

  • dididadidida Member Posts: 4
    Thank you very much. I will try. It has 2H,4H,N,4L and it's part time 4WD.
  • cliffy1cliffy1 Member Posts: 3,581
    Yes, the 96 was a part time system. Engage it on dry pavement and pull forward slowly while trying to turn a corner. The steering wheel will bind if the system is working.
  • pschreckpschreck Member Posts: 524
    Cliffy,

    As always, thank you for your efforts. My question is regarding the power split between the front and rear differentials when driving in 4wd high. Is it 50/50 or something else?

    Thanks
  • cliffy1cliffy1 Member Posts: 3,581
    Yes, it is my understanding that is it a 50/50 split if traction is equal at each side.
  • wwestwwest Member Posts: 10,706
    speaking of that..

    When I bought my first RX I seem to remember the salesman telling me the torque split was 70/30 front/rear, now Lexus seems to be saying 50/50. I know they haven't changed very much in the drive train becuase the same 1998 AWD transmission/differential/transfer case shop manual is used for all.

    I recently learned that the new highlander has a final drive ratio in the front of 3.xx/1 and rear of 2.9xx/1 (don't remember actual numbers) a difference of about 12%. Is this how they get the torque split?
  • pschreckpschreck Member Posts: 524
    Thanks cliffy and Happy Holidays!
  • leomortleomort Member Posts: 453
    Cliffy,

    I seen in Edmund's review that 1999 MY 4Runners also come with AWD. Is that only for the "Limit" edition?

    Thanks,

    Leo
  • rljslickrljslick Member Posts: 59
    Don't know about your 1999 4Runner, but all the new 4Runners come standard with ABS.
  • cliffy1cliffy1 Member Posts: 3,581
    The '99 Limited did have an AWD system, but it was not the same ActiveTrac system of today.
  • spdmtr5spdmtr5 Member Posts: 111
    That is what it says on the back of the HL.As I understand their system it is fwd with a viscous clutch that transfers power to the rear wheels when slippage occures.I don`t call that real 4WD.
  • cliffy1cliffy1 Member Posts: 3,581
    The HL is not a front wheel drive with on-demand rear power. Go back and read the first several posts in this topic. It is a 50-50 power split with a viscous coupling center differential.

    As to whether that is a "real 4WD", we are in a discussion of semantics.
  • wwestwwest Member Posts: 10,706
    All I can tell you is that with the 2001 RX's rear wheels elevated the front wheels will try to "drive" over a set of chocks while the rear wheels spin freely in thin air. In the reverse position the rear wheels don't seem top get any torque at all.

    The only disparity I can find that might cause this is the fact that the final drive ratio to the front is 3.2xx/1 vs 2.9xx/1 for the rear, the same for both the HL and the RX. But in my mind this ratio disaparity should help route torque to the rear.

    It is possible that the VC just simply doesn't have enough overall pre-load to get the job done except maybe under really severe or extreme conditions.

    No one has yet been able to get Lexus to weigh in on this matter, so the suspicion is that you are right, the RX and the HL AWD versions are both predominantly FWD.
  • cliffy1cliffy1 Member Posts: 3,581
    The center differential is a LIMITED slip. LSD's can be overcome if there is no traction. This situation causes all power to be routed to the slipping wheels. This is why the test video by Mercedes is a trick. They rigged it so the front tires had no traction. If they even had a little, power would have been sent to the rear.

    I assure you, the HL is not a front wheel drive if you have the AWD (AKA 4WD) model.
  • wwestwwest Member Posts: 10,706
    The RX300 AWD has an "open" center differential with a VC accross the two "output", front/rear, drives. With disparate turning rates between the two differential outputs the VC should tighten up and limit the amount of the disparate turning rate regardless of the cause.

    It didn't seem to "work" in my 2000 RX300 AWD so I traded up to the 2001 RX300 AWD with VSC and TRAC on the assumption that TRAC would force engine torque to the wheel(s) with traction.

    It doesn't seem to work and Bellevue Lexus says my VSC and Trac are fully operational. I'm sure that I have felt the VSC kick in a few times but so far not the TRAC function.

    Does anyone have an answer about the disparate final drive ratios?
  • wwestwwest Member Posts: 10,706
    So, if my front wheels happen to be setting on a patch of very slippery ice and my RX AWD won't move forward or backward that's simply a TRICK by mercedes?

    Not a TRICK at all, it simply, and correctly, shows one of the short-comings of the RX AWD system versus the ML's.
  • spdmtr5spdmtr5 Member Posts: 111
    can a HL with it`s nose stuck in a snow bank and the rear wheels on dry or sanded pavement back out?
  • wwestwwest Member Posts: 10,706
  • bradfordl1bradfordl1 Member Posts: 18
    Dose anyone have the answer to this one? We know that the Sequoia 4wd system takes a while ( and what is a normal wait time for that?) to engage once the button is pushed........what if you are in 2wd, get stuck in a slippery situation, push the 4wd button and the light blinks........you are unable to move - will the system engage without moving the vehicle?? Not a very good situation for a 4wd vehicle if you can't enage it when you need it. Thanks..............
  • spdmtr5spdmtr5 Member Posts: 111
    It seems to me when you pay 30K for a "superior traction" vehicle you should have the option to lock it into a 50/50 split and have a low range.The option to purchase a LSD should also be offered.And........it should be RWD so you can steer with your right foot.
  • wwestwwest Member Posts: 10,706
    The problem is that neither the RX nor the HL is being sold as a superior traction vehicle, there are just different looking minivans.
  • aggiedogaggiedog Member Posts: 238
    Bradfordl1, I was told by a Toyota Service Manager that there are a couple of reasons why it may take a while for the 4wd to engage. 1) Cold weather. Apparently the differential fluid is not as "fluid" as in warmer weather. 2) Speed.

    His suggestions: Try to engage the 4wd when the truck is off. It's usually on when you start the truck. Also, if your truck is already running, just put it in reverse or drive and it should pop in. I've found this to work quite well.
  • wwestwwest Member Posts: 10,706
    After I put two brand new tires on the rear of my jeep it became hard to engage 4wd sometimes I had to back up slowly for a short distance before it would engage.
  • cliffy1cliffy1 Member Posts: 3,581
    The reason it sometimes takes longer to engage is that there is constant stress on the transfer case. Until this stress is let off, it can't engage the front wheels. If you are driving up hill and hit the button, let off the gas pedal and then hit it again. This will get it to engage immediately. Driving down hill is also easy and requires a quick tap on the brake.

    If you are already stuck, hit the button and then the gas pedal a time or two. It will jump right in.
  • bradfordl1bradfordl1 Member Posts: 18
    Thanks to cliffy1 and others who given advice.......so far it all makes and sense and I went and test drove one at the dealer and it works! Next question ( which I forgot to check out the first time ) is if you are in 4wd bring the vehicle to a stop to shift into 4wd low and shift the trans. into low.........is there a lag time for the center diff. to lock?? Or will that lock immediately? Thanks again!
  • cliffy1cliffy1 Member Posts: 3,581
    Hmmmm... I don't know. I've never tried it. I suspect it would go in as soon as you added torque, but I will not swear to it.
  • bradfordl1bradfordl1 Member Posts: 18
    Thanks for the thoughts...........maybe an owner out there might try it and let us know! I don't own a Sequoia but I am advising my dad ( 84 yrs old!) who does own one and lives in the hills or Vermont and faces some interesting weather!
  • cliffy1cliffy1 Member Posts: 3,581
    Were I you, I would instruct him to put it in 4WD and leave it there to avoid any confusion or problems.
  • bradfordl1bradfordl1 Member Posts: 18
    Yeah....that was pretty much what I figured too.......I still would like to know if the lock in of the center diff. is instant or lag......even though I don't think he will ever need it given the capability of the 4wd/active track system. Part of the problem for some people ( and older people in particular ) is that the system is so shophisticated and Toyota ( and other foreign car manufacturers ) have problems in the translation of their owner's manuals from the Japanese( in this case) to English.. Thats compounded by the fact that the manual writers and translators probably don't fully understand the systems either. At least that has been my experience.......
    Thanks for your advice!
  • sandman14sandman14 Member Posts: 6
    What is the top speed can you can drive in 4wd. I have heard it is 62 mph and I have heard there is not speed limit. I'm looking for the straight scoop.
  • wwestwwest Member Posts: 10,706
    Now there's a fundamentally non-bright question!

    If the conditions are such that you are able to drive over 45 you obviously don't need 4WD so why would you want to know the answer to this question...

    Sure, you maybe could still maybe go faster in 4WD, but why PUSH the performance envelope, the results can be much more expensive than "pushing" a Pentium.

    Let the road conditions and safety determine the drive mode.
  • cliffy1cliffy1 Member Posts: 3,581
    Actually, your's is a good question and there is a good answer as well. While you must drop below 62 MPH to engage the 4WD system, once engaged, there is no specific limit to how fast you can drive. You only need to slow down to engage it.
  • wwestwwest Member Posts: 10,706
    Why would anyone, except in a racing venue, continue to run in 4WD above, say, 45MPH?

    4WD now, NOT AWD.

    Would that be anything but a waste of perfectly good gasoline?

    And if your excuse is that the roadbed is slippery.... and you're driving above 45MPH?
  • cliffy1cliffy1 Member Posts: 3,581
    You're combative attitude is mystifying. Had you read the previous posts in this thread, you would see that the Sequoia IS an AWD when the 4WD is engaged. Further, you would note that owners have reported no drop in fuel economy. The Sequoia 4WD system is designed to work best when engaged. There are plenty of times where AWD would be a benefit, even at higher speeds.
  • pschreckpschreck Member Posts: 524
    I agree with cliffy. I run my Sequoia in 4wd in the rain or on dry roads at speeds of 65 and higher all the time. It handles very well at speed. No, it's no Porsche, but then what good is a Porsche in the snow? The 4wd system in the Sequoia is the best of both worlds of 4wd and AWD. I recommend that anybody new to this page read the earlier posts about this system. It should clear up any dispute as to the difference between a bright and a non-bright question.
  • sandman14sandman14 Member Posts: 6
    Since this board is supposed to share knowledge, let me clarify something to you wwest.

    I was told by a Toyota Sales Rep. that if you are in 4wd and you go above 62 mph, you would damage the transfer case. I don't own the vehicle yet and do not have the owners manual. I guess by your condescending attitude you must own one.

    If someone were to drive the vehicle past the "4wd limit", not realizing that they were in 4wd drive, and there is no auto shut-off that would turn off 4wd at the 4wd max. speed limit, they would damage the vehicle. I don't plan to consciously be aware of whether or not it is in 4wd all the time.

    Maybe you like to buy the second vehicle after you have damaged the first one trying to figure out how it works. I don't. I'm sorry that Santa didn't give you what you wanted for Christmas, but take your frustrations out on someone else.
  • wwestwwest Member Posts: 10,706
    sandman14, I think I'm on your side.

    definitions first:

    AWD: drives all four wheels but in some manner that no damage will be done to the drive train on high traction pavement.

    4WD: For low traction surfaces only, damage to the driveline will likely occur if driven on high traction surfaces in this mode for very long regardless of speed.

    Ergo: Asking how fast one can drive a 4WD is a non-bright question. It shouldn't be driven in this mode at all at ANY speed on a high traction surface, and it would take an idiot to drive at high speed with 4WD engaged since it should only be engaged on a low traction surface!
  • bradfordl1bradfordl1 Member Posts: 18
    Since the Sequoia becomes an AWD when the 4wd button is pushed.......this whole speed question is irrelevant as far as "damage to the system," isn't it?
  • cliffy1cliffy1 Member Posts: 3,581
    In the old days, Wwest's definitions were correct. Part time systems could not be safely driven on dry pavement which meant that speed was limited by road conditions. The Sequoia (and 4Runner) defy the normal definitions. They are technically part time systems because they are not always engaged. When they are engaged, they behave like AWD systems. Sandman's question was not a stupid question in light of this. Wwest simply decided to abuse him by using an old definition of AWD and 4WD.

    Now the question is: Who asked or responded in a "non-bright" manner?
  • tidestertidester Member Posts: 10,059
    ... that's the topic here - not personalities! Thanks!

    tidester
    Host
    SUVs
  • wwestwwest Member Posts: 10,706
    don't die, and they don't even fade away...

    If you have another, newer, definition for AWD, then let's hear it. Same goes for 4WD.

    In the meantime "full time" "four" wheel drive is something relatively new to the marketplace, brought about primarily by the recent availibility and low expense of the viscous clutch. It seems to me that most manufacturer's have been long settled on the "MODERN" AWD term to distinguish these "full-time" automatic (no operator intervention required) 4 wheel drive systems.

    Now, the question was "when is it safe to "switch" in or out of 4WD mode?".

    If the system is "switchable" then it is clearly not intended to be truly an AWD (full-time, no operator intervention) system at least not as currently defined by the manufacturers themselves.

    My 1992 Jeep had RWD, AWD (full-time), and 4WD (part-time) modes.
  • wwestwwest Member Posts: 10,706
    It is my understanding that when a 4WD system is labeled "part-time" that means that portions of the drive train are susceptable to damage if the vehicle is driven in this mode on high traction surfaces or even intermittent snow/ice and high traction surfaces.

    Everything I can find indicates that the Sequoia is a part-time 4WD system with a locked center differential in 4Wd mode. That means it CAN be damaged by driving in 4WD mode on high traction surfaces.

    An explanation, Maybe.

    My thinking was/is if the 4WD mode can ONLY be used on "constantly" slippery surfaces then why would anyone want to go faster than say 45MPH on a constantly slippery (black ice?) surface?
  • pschreckpschreck Member Posts: 524
    Read the beginning of this forum or buy the vehicle and try it. The center diff is NOT locked unless you WANT it locked.
  • cliffy1cliffy1 Member Posts: 3,581
    This entire topic was started by me after answering this same question repeatedly in the Sequoia and Land Cruiser topics. I strongly suggest you go back and read the first three posts on this topic before inserting your foot farther into your mouth. You will discover that it is fairly difficult to lock the center differential on the Sequoia and the system was designed to run in 4WD. In fact, the Sequoia 4WD system is identical to the Land Cruiser except for the fact that it can run in 2WD.

    Until you actually read and comprehend this information, you need to relax a bit.
  • wwestwwest Member Posts: 10,706
    But I worry about someone asking these kind of questions. You and I have no way of knowing the person's (asking the question) background or experience level and most salesmen are more than willing to mislead them or let them mislead themselves.

    How many people buying 4WD vehicles are aware that part-time MEANS not even on partially slippery roadbeds? That's a really expensive lesson to learn the hard way.
  • cliffy1cliffy1 Member Posts: 3,581
    So... let's make sure I understand this. A participant asks a question about engaging the 4WD system on his Sequoia. The Sequoia is technically a part time system since it is selectable. Because other part time systems are hazardous to use on dry pavement, you called his question "non-bright."

    Now, even if the participant was asking about engaging the 4WD on a Tundra, your answer was rude. As it is, you answer was rude and wrong.
  • wwestwwest Member Posts: 10,706
    part was asking if it was okay to use 4WD mode at HIGH SPEEDS, 62 MPH was mentioned. My first mistake was assuming that everyone would know that a "part-time" system should NEVER be engaged on non-slippery surfaces.

    If (any) systems cannot be used on high traction surfaces, only on slipping surfaces, why would anyone be asking how fast can I drive my "system".

    And, by the way, did you mean to say the 4runner and the sequoia share the same 4WD setup?

    The Landcruiser has been around a long while and I doubt that Toyota would change its 4WD setup this radically.
  • wwestwwest Member Posts: 10,706
    "I was told by the Toyota saleman that if I drove above 62 MPH in 4WD I could DAMAGE the transfer case."

    "I don't plan to be consicously aware of whether or not its in 4WD all the time".

    Basically he's asking US to put the lie to what the saleman told him! Now I know the saleman likely, probably doesn't know what he's talking about, but if I were him I wouldn't trust any of us either. Obviously even we are of two opinions.

    So as I said, let the driving conditions and safety determine your maximum speed.
  • wwestwwest Member Posts: 10,706
    Now I think I see the problem.

    You apparently think that becuase you defined
    "part-time" drive setups earlier in this forum that your definition "holds".

    NOT!

    I wouldn't have any trouble abiding by your definition had not the industry long ago decided that Part-time meant a system that could not be used full-time (do you get that?), as on high traction surfaces.
  • cliffy1cliffy1 Member Posts: 3,581
    This is the last time... He owns a SEQUOIA. His salesman was wrong.

    Yes, the Land Cruiser, 4Runner and Sequoia share the same Active-Trac 4WD system with the caveat that the later two can be placed into 2WD if desired (ergo: part time). The Land Cruiser system changed in MY 2000.

    While I agree that driving conditions dictate driving speed, this has no impact on his 4WD system in the SEQUOIA.

    Finally, you are trying to weasel out of the fact that you have been giving bad information by using a semantic argument. "I wouldn't have any trouble abiding by your definition had not the industry long ago decided that Part-time meant a system that could not be used full-time (do you get that?), as on high traction surfaces." What "industry" decided this? The only definition of part time I have ever heard is one that can be selectively engaged and disengaged. The Sequoia fits this definition, yet is perfectly safe to use in any traction conditions.

    Now stop it.
  • wwestwwest Member Posts: 10,706
    Just where have you been for the last 20 years or so?
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