Edmunds dealer partner, Bayway Leasing, is now offering transparent lease deals via these forums. Click here to see the latest vehicles!

Toyota 4WD systems explained

1…3536384041…49

Comments

  • brightness04brightness04 Member Posts: 3,148
    Very much in agreement.
  • kdhspyderkdhspyder Member Posts: 7,160
    This is accurate.
  • wwestwwest Member Posts: 10,706
    Clutches, LSD, etc, that are used to apportion engine torque to non-slipping wheels will eventually wear out. But unless you live in a heavy use area, say MT or AK, they may very well outlast the usefulness of the overall vehicle.

    But in the meantime you will have a much more robust and reliable LSD, AWD or 4WD system wherein no engine dethrottling will be required to preserve the brake rotors.

    And please note that many of these brake apportioning AWD systems only allow AWD "activity" for about a minute or so of semi-continuous operation before disabling the ABS pumpmotor to prevent its failure from overheating.
  • nobody3nobody3 Member Posts: 27
    Hi,
    2006 RAV4's "On Demand 4wd" is basically 2WD with extended control traction like Honda CRV and Quadra TRAC II. True, the transfer clutch wear will be minimum since it will be very rarely used in most typical usage. (Unlike CRV, MDX engages the transfer clutch every time it accelerates (0-18MPH) thus having more wear). Highlander & MB MClass also use extended traction control but the difference is, they are AWD all time and hence the chance of slippage is reduced very much, unlike the new RAV4. In Highlander, the traction control is used just until traction is regained. Neither ABS nor TC is turned off because of heating. Highlander AWD system is simple and neat for most purposes. Of course, it is not necessarily meant for the Rubicon trail. Agreed, there are a few other true all terrain vehicles but they are more expensive and sometimes less reliable.
  • wwestwwest Member Posts: 10,706
    That many folks think the three open diff'l in the HL or Rx will provide any more get up and go traction than a simple RWD. With either one if ANY one wheel slips then all drive torque is instantly LOST.

    Both instances are commonly known and recognized by the public as being simple ONE-WHEEL DRIVE vehicles.
  • nobody3nobody3 Member Posts: 27
    Sorry that I have to disagree. As per one test, Mercedes M Class successfully passed the Rubicon Trail Test, but with some struggle. I guess, it is good enough test that counts. I doubt very much if any RWD (even with sporty wide tires) can make it. I think RWD, FWD, AWD and 4WD, all have their own place and purpose. Hope people will choose wisely based on their need.
  • morey000morey000 Member Posts: 384
    WWEST,
    point well taken. most of these AWD systems are not all that useful when conditions get rough. I'm amazed at how easily I can spin some wheels on my Passat 4motion in the snow. My 4X4 '99 Blazer, when locked into 4WD-hi does much better, and better still when I go into Low range and the center differential is locked.

    What can you tell us about the 4WD system and capabilities of the new Rav4 when put into 4WD mode?
  • wwestwwest Member Posts: 10,706
    I was seriously considering getting one for a MH TOAD until I discovered no "stick". Sounds like a good AWD concept and I would expect to see the same system in the RX, HL, and Sienna fairly soon.
  • jmayjmay Member Posts: 1
    is this the system that is 2WD and goes into 4WD when wheels slip? I am suppose to have this but owners manual says nothing of it. the back has an emblem that has 4WD. does anyone else know of this? and I say a post on snow ect. how does this work?
  • tlttlt Member Posts: 2
    Are larger wheels -- 17 inch -- a benefit or detriment to offroading and driving on pavement with a 2006 4wd 4Runner, v6?

    Thanks.

    TLT
  • russlarussla Member Posts: 74
    People think(or rather know) a full time 4wd system is better, than RWD alone because the 4wd car provides better traction, especially when accelerating.

    it's true that with open diffs the torque will go to the slipping wheel. Just as with the RWD with an open diff.

    The 4wd fulltime advantage is that each tire now is driving the car, so the chance of breaking one of the drive wheels loose is greatly reduced. (by half)

    Think of it this way, with RWD only, the torque that needs to be transfered to the road must go thru only two tires, thus they need twice as much grip.

    With a full time system, the torque/friction requirement to accellerate per tire is 1/2 of the RWD set up,

    So, with the same tires, and the same slippery surface, the same car with 4wd, rather than rwd, could accelerate twice as fast. Or drive up a steeper hill, or up a more slippery hill.

    best regards
  • wwestwwest Member Posts: 10,706
    Your theory only applies if all four wheels have equal traction. The front wheels have the advantage(??) of engine weight bias and many Toyota/Lexus vehicles use a different final drive ratio at the front versus the rear such that virtually no engine torque is provided to the rear wheels.

    Be that as it may when it comes to my need for excersizing directional control or maintaining directional control I NEVER want my stearing, front, wheels to have ANY traction responsibility other than laterally.
  • pschreckpschreck Member Posts: 524
    "Be that as it may when it comes to my need for excersizing directional control or maintaining directional control I NEVER want my stearing, front, wheels to have ANY traction responsibility other than laterally."

    Maybe I'm stupid Willard, but what are you trying to say here? :confuse:
  • tidestertidester Member Posts: 10,059
    I may be wrong but I think he's just saying he prefers RWD. :)

    tidester, host
  • wwestwwest Member Posts: 10,706
    Both the new Lexus IS and GS AWD versions have a system wherein engine torque, leading and lagging, can be routed away from the front and primarily to the rear if directional control is threatened, freeing the front traction solely to lateral control.

    Great idea.
  • pschreckpschreck Member Posts: 524
    Oh. Thank you.
  • pschreckpschreck Member Posts: 524
    I get it now. Duh. :)
  • russlarussla Member Posts: 74
    I disagree, the wheels don't need equal traction, they each need the minimum requirement of traction to be met. As long as each tire has the min required to meet the accel requirements, it doesn't matter if one or two are on higher traction areas.

    Your preference may be for Rwd vehicles, and one might successfully argue that they are sufficient with the right tires and driver for most situations. For people in warmer climates it may definately be the case.

    But that doesn't erase the fact that 4wd just cars go better in slippery conditions regardless of the driver.

    Best regards
  • wwestwwest Member Posts: 10,706
    No, I stand firmly in favor of AWD or 4WD just as long as some way can be found to remove engine drive torque or engine compression braking at the front when the front traction is low enough that it can just barely provide enough lateral roadbed adhesion to keep me moving in a straight line or allow me to turn when necessary.

    Otherwise I'll stick with RWD, or rear biased AWD, and not put my life at risk, thank you.

    "...4Wd cars just go better in slippery conditions..."

    Granted, adsolutely!

    But now let's talk about operations at the very limits of roadbed adhesion...

    What about stopping? 4WD is no help there, and might even be detrimental if engine compression braking is high enough to make ABS non-functional.

    And what about turning? 4WD can actually be detrimental!
  • nobody3nobody3 Member Posts: 27
    Diverting the engine power or engine braking to just two wheels is not good. Based on one test by a car magazine, awds faired much better than fwds on under-steering and rwds on over-steering. And generally over-steering is worse than under-steering. The idea of braking is to dissipate the energy in the brake pads or as engine compression rather than slipping the tires. Once the tires start slipping, the traction goes down dramatically (just like initial inertia). Basically CRV and RAV4 are fwds until you start slipping the front. These cars just give the taste of an AWD. (Like a toy guns and sometimes people are fascinated). Yes, these are better than 2wds but not as good as real 4WD/AWDs.

    Coming to variable torque drives (VTM-4) they are good for fuel efficiency/good acceleration etc., (especially, with bias on the rear on dry pavements) but many times these cars also give the option of locking at 50:50 torque distribution for better traction in bad situations like ice.

    Sporty and safety are two different things. People have their own preference, I guess.
  • ustazzafustazzaf Member Posts: 311
    And what about turning? 4WD can actually be detrimental!

    Ya, God forbid should you have wheels up front pulling you through the corner as opposed to being pushed straight ahead by the rear wheels!!!! The only time that 4wd is not goig to help in a corner is if the wheels are locked up because you have braked too hard and/or the anti-lock failed. Even then, the 4wd will not hinder.

    What about stopping? 4WD is no help there, and might even be detrimental if engine compression braking is high enough to make ABS non-functional

    What does anti-lock do? Keeps the wheels from locking up. What happens if the wheels get power? They continue to turn, allowing for control. I grew up in North Dakota, and anyone who has actually driven on ice to any extent knows that the constant compression slowing down is much better than intermittant braking for maintaining control. Of course if you want to go from 60 to zero in the lenght of your car, 4wd will not help, but about the only thing that will is a massive log chain wrapped around a solid structure or a couple JATO rockets pointed blasting forward.
  • wwestwwest Member Posts: 10,706
    "..pushed straight ahead by the rear wheels...."

    "...wheels up front pulling you through the corner..."

    Apples and Oranges comparison. If there is enough traction for the front wheels to "pull" the FWD vehicle around the corner then clearly there is an EXCESS of traction for lateral control at the front of a RWD vehicle.

    ABS cannot alleviate, moderate, engine compression braking at the front wheels of a FWD vehicle. The only way to do that is to release the clutch with a stick shift, shift into neutral with an automatic, or maybe have the DBW aspect of the engine/transaxle ECU match the engine RPM to the rate of rotation of the rear wheels.

    And yes, back when I lived in MT (before FWD) if engine compression braking at the rear didn't suffice then a slight application of the parking brake often helped.
  • ustazzafustazzaf Member Posts: 311
    I was comparing 4wd to RWD. Never mentioned FWD. It was mentioned that 4wd could be a hinderance in a turn. As long as the 4WD is engaged, the clutch out and the engine is running, the wheels will not lock, and will help with turning. Once you depress the clutch, you have no wheel drive. However, the front and rear will still be locked, so if the front is turning, the rear will be too. So if you are coming up on a turn and hit a ice patch with the front wheels, the rear wheels will keep the front tires turning to increase traction.
  • iqbaldhillon2iqbaldhillon2 Member Posts: 116
    I have a Prerunner its like a 4x4 but offers better gas milage and still same feel as 4x4 Tacoma.
  • chiefjojochiefjojo Member Posts: 39
    Does anyone have any info on the differences between the pre-2003 A-TRAC 4WD system in 4Runners and Sequioas (& TLCs?) versus the Torsen-based system implemented in 2003? I had heard that the improvements in the system were substantial. I have a 2002 4Runner with the older A-TRAC system, which seems to work very well as I've never gotten stuck offroad--but also haven't been on any dificult trails.
  • 2toyotas2toyotas Member Posts: 104
    The 4Runner was redesigned in 2003 and received a torsen center differential in the transfer case instead of an open differential. The power split front and rear is 40/60 under normal conditions. The torsen unit can send up to 53% to the front, and 71% to the rear instantly if it senses slip. Traction control now works separately on each axle, so even when the center diff is unlocked both axles always get power. That is the major difference, with the old system all the power could go to one wheel because A-TRAC controlled all 4 wheels together. The Sequoia got this setup on the 2005 model year, and the Land Cruiser still has the old system. Both systems are great, but with the new one you really never have to lock the center differential. When you lock the center diff both systems are identical, the split is 50/50.
  • kullenbergkullenberg Member Posts: 283
    The other thing about locking the center diff. on the current system, that is worth mentioning, is that it disables the engine cut back on the traction control. This is useful when going up a slippery grade, where you want to maintain momentum.
  • 2toyotas2toyotas Member Posts: 104
    Thought this was interesting. During our last snow storm, which was 18 inches my brother and I went to an unplowed lot which had a nice hill. He has a V6 4Runner and I had my Double Cab Tundra. Both had Blizzak snow tires on them. My Tundra does not have VSC or Trac, just a plain Limited Slip rear differential. We both tried the hill in 2WD, and both got stuck near the bottom. He switched to 4WD unlocked and continued with no problem at all. I switched to 4WD, and it still would not move. I had to switch to 4LOW, and it then walked up with no problem. My point is this, after getting stuck pretty good in 2WD, it was much easier to get unstuck with A-Trac. My Tundra has an open differential in the front, so it did not help much. I have a Sequoia, a 4Runner, and a Tundra, and when it snows the Sequoia and 4Runner are more sure footed than the Tundra. They plow through everything like a walk in the park.
  • chiefjojochiefjojo Member Posts: 39
    "Traction control now works separately on each axle, so even when the center diff is unlocked both axles always get power. That is the major difference, with the old system all the power could go to one wheel because A-TRAC controlled all 4 wheels together."

    Is that a good thing? I mean if you are going offroad you need to lock the center diff anyway to disengage the VSC and TRAC (not A-TRAC), to allow for more wheelspin. If three wheels are spinning due to ice or whatever the case may be, then isn't it an advantage to have A-TRAC send all the power to one wheel, instead of to one wheel on each axle?
  • 2toyotas2toyotas Member Posts: 104
    The Torsen center differential sends the power from front to rear. Lets say the two front wheels were on ice, and the left rear was on ice. The Torsen would instantly send 71% to the rear, A-Trac would brake the left rear, so the power would go to the right rear, and as long as the traction was the same on the two front wheels, they would split 29% of the power. It keeps good momentum. The big difference is on inclines. One wheel is sometimes not enough to pull a vehicle uphill. I had an 03 Sequoia, an on several instances I had to lock the center diff. to get up my driveway in heavy snow or ice. I now have an 05 and I never need to lock the center diff., because the Torsen always supplies some power to each axle. It helps keep momentum, and it saves A-Trac from always kicking in. If both wheels on the front were on ice, the Torsen would simply send more power to the rear without A-Trac ever kicking in. In my opinion it is one of the best systems available.
  • ustazzafustazzaf Member Posts: 311
    Thought this was interesting. During our last snow storm, which was 18 inches my brother and I went to an unplowed lot which had a nice hill. He has a V6 4Runner and I had my Double Cab Tundra. Both had Blizzak snow tires on them. My Tundra does not have VSC or Trac, just a plain Limited Slip rear differential. We both tried the hill in 2WD, and both got stuck near the bottom. He switched to 4WD unlocked and continued with no problem at all. I switched to 4WD, and it still would not move. I had to switch to 4LOW, and it then walked up with no problem. My point is this, after getting stuck pretty good in 2WD, it was much easier to get unstuck with A-Trac. My Tundra has an open differential in the front, so it did not help much. I have a Sequoia, a 4Runner, and a Tundra, and when it snows the Sequoia and 4Runner are more sure footed than the Tundra. They plow through everything like a walk in the park.

    I find that very interesting. For one thing, I never had any trouble in snow, mud or anything else with my Tundra in 4High. Also, switching to 4 low does nothing but increase power. It does nothing at all for traction. Infact, low range can be a disadvantage in snow and ice because of the added torque.
  • 2toyotas2toyotas Member Posts: 104
    My Tundra would have plowed through the lot and up the hill with no problem in 4High, but I wanted to see how far I could get in 2WD. It did OK until I started up the hill, the tires began to spin, and it would not move. I needed to go to 4Low to continue. You better do your homework on this one because 4Low adds torque, but with very little wheel spin. It absolutely gives better traction, and is a big advantage to move on snow and ice. It puts a lot of torque to the wheels to move the vehicle, while you creep along. Spinning the rear wheels in 2WD buried them and switching to 4High only added one front wheel, because of the open front diff. The vehicle still would not move. I could have spun the wheels to try to move it, but why heat up the limited slip diff, when 4Low moved me up the hill with no problem.
  • wwestwwest Member Posts: 10,706
    Sorry, I have to step in and disagree on this one. 4-low only allowed you to use your leadfoot a little more effectively. In 4-high you were being too agressive on the throttle. You didn't get more traction in 4-low, you just reduced the "gain" of the accelerator pedal, not as much potential for wheelspin.

    4-low vs 4-high increases the level of torque available at the drive wheels, not the level of traction.

    You could have very likely accomplished the same thing in second or even third gear, and quite possibly even in 2WD. Next time try feathering the throttle just a bit to the point wherein the tires do not quite break traction with the surface.
  • 2toyotas2toyotas Member Posts: 104
    First of all I was not heavy on the throttle at all. Second , instead of trying all that, I put it in 4Low and it moved with no problem. Call it what you want! 4Low multiplies the torque applied to the wheels, in turn giving you the ability to move the vehicle! Sounds like more traction to me. I was trying to see how far it would go in 2WD before struggling. It dove through the lot, but struggled to go up the hill. I was not going to heat up the limited slip diff, when I could simply put it in 4Low and continue. How many RWD vehicles drive through 18 inches of unplowed snow, let alone a steep hill? My point was the 4Runner with A-Trac continued up simply by engaging 4High unlocked. He did not have to feather the throttle or try putting it in second or third gear. He pressed the gas, and continued on. The Tundra did not. In my opinion, I would rather have A-Trac then a Limited Slip rear Diff. in the snow.
  • harboharbo Member Posts: 136
    What wire did you pull to disconnect the Traction Control?
  • harboharbo Member Posts: 136
    How do I permanently disengage the Traction control so I the engine power is there to use in loose sand, mud etc.? The stepping on and off the emergency brake etc etc etc everytime is a pain.

    slvrfx :shades:
  • nobody3nobody3 Member Posts: 27
    Thanks for the interesting information.
    I agree, one would get high torque with 4LOW. But, I think it is the reduction in wheel rotation rate associated with 4LOW that helped to get better traction. Like taking baby steps when the surface is slippery.
    Concur in other deductions.
  • wwestwwest Member Posts: 10,706
    If you unplug the MAF/IAT module connection, just downstream of the engine air filter, while the engine is running the engine will die. Plug the connection back in and restart the engine.

    Except for an engine check light being on everything will now operate as normal except for VSC/Trac which remain disabled until the check engine light clears after about 4 drive cycles.

    Instruction given to me by the service manager at Lexus of Bellevue WA.
  • wwestwwest Member Posts: 10,706
    Yes, less wheel "speed" for a given level of accelerator pedal travel, making it a lot easier to "feather" the throttle.
  • harboharbo Member Posts: 136
    Thanks WWest, I wonder if the same may work on my 02 Lexus GS 300??
  • ustazzafustazzaf Member Posts: 311
    Atleast someone understands. The only way to increase traction by shifting from high to low is if a locker kicks in when you shift down. That is the case with my Tacoma. I have to be in low for the locker to kick in, so I DO get better traction in low. Aside from that, it is all in how much gas pedal you apply. The exact same wheels will get power in high or low.
  • wwestwwest Member Posts: 10,706
    "....understands..."

    No, all the traction you can use already exists as a function of things like stiction of the tire surface with the roadbed, weight of the vehicle, etc. The only ways I know of to INCREASE traction readily is to add weight, sand bags, and/or studs or chains.

    What this discussion is about is how to make the best use of the traction we already have, as in distribute the engine torque over a greater contact area (locker) and/or make it easier for the driver to modulate the torque, feather the throttle, at a much lower level (granny-grunt gear ratio).

    Not by any means saying the locker didn't engage in a shift to low range, but what I've been trying to point out if that the effective "gain" of the accelerator pedal was also reduced significantly.

    In many instances the best way to get going initially is to just "ease" the throttle open ever so gently and slowly. If you happen to be driving a new Corvette that might be really difficult. The Corvette engine has so much torque at the low end it is practically impossible to "soft" start it.

    But reduce the final drive gear ratio to 100:1 and even full throttle wouldn't move the car forward fast enough for the TONS of torque now available to break traction.
  • frisinafrisina Member Posts: 1
    I have a 2006 Tacoma 4x4 double cab, with TRD Offroad package.

    In a previous 4wd SUV, I had several options with regard to 4wd. The first was a "Full Time" 4wd, which meant the center diff. was NOT locked, allowing to drive on dry pavement - without risk of damage.
    Next, there were the traditional 4hi and 4lo, that locked the center diff, and were only for slippery (off road) conditions.

    Now the question:
    On my Tacoma, when in 4hi, is the center differential locked? The manual indicates that it is for slippery, or wet pavement. But in my experience, wet pavement may not provide enough "slip" to operate a true 4wd system, where the center diff is locked, without risk of torquing the drive train too much.

    I hope I've explained my question well enough. Any info would be appreciated.
  • abbylouabbylou Member Posts: 33
    I was just wondering when operating the 4-wheel drive system, when should I dis-engage the traction button on the the left side of the dash? If I drive in occasional snow on the hwy or neighborhood, shouldn't I just push the four wheel drive button? I have heard some folks speak about dis=engaging that button?
  • benzy1benzy1 Member Posts: 11
    Frisina, you dont have a center differential (CD), you have a transfer case, which operates effectively like a permanently locked CD.

    Check out this very good summary.

    cliffy1, "Toyota 4WD systems explained" #4, 16 May 2001 4:00 pm

    You may want to check out the first 5 posts to this thread (authored by cliffy) to get a good understanding of the pros and cons of your (and my) tacoma 4wd system.
  • johnxyzjohnxyz Member Posts: 94
    Would someone please eplain or elaborate on the new FJ Cruiser with a manual tranny has full-time AWD vs. part-time AWD with an automatic transmission?

    Isn't the auto tran FJ the same as the auto tran 4Runner, which has a F/T AWD system?

    Is the FJ with auto the same as the new Rav4 with auto (so then these 2 models are different from the 4Runner with auto)? Confusing...

    Thanks alot.
  • wwestwwest Member Posts: 10,706
    Pardon me but....

    This does not address the Tacoma specifically but...

    No 4X4 can be operated on a high traction surface absent an "open" center diff'l of one type or another. The only difference between a "transfer case" and a center differential ("case") is that the transfer case contains both a CD and a low range gearset along with the ability to lock the center differential during times of operation on poor traction surfaces.

    There are, currently in the market, part time 4X4 systems without a "transfer case" and only an open differential that can be locked for part-time use on low traction surfaces.
  • benzy1benzy1 Member Posts: 11
    I have no idea of what you are tying to say here wwest...

    But yes. Since the Tacoma does not have an open center differential, then it would be detrimental to drive the car on dry pavement while 4wd is engaged.
  • 2toyotas2toyotas Member Posts: 104
    The FJ with a manual trans has the same transfer case as the V8 4Runner. The FJ with an auto trans has a different transfer case. It does not have a center differential in it, so it can not be used on dry pavement. It is the same transfer case used on the Tundra. Once you put it in 4WD both axles are locked together, so there will be binding around turns. The RAV4 uses a totally different type of system. For 06 it is now an On Demand AWD System. The RAV4 is primarily Front Wheel Drive until there is a need for extra traction, then a clutch near the rear differential engages the rear wheels. The major difference between the RAV4 and the FJ and 4Runner, is that the RAV4 does not have a 4LOW option.
  • ustazzafustazzaf Member Posts: 311
    If you are driving with the 4WD locked in while taking sharp turns on dry pavement, you may cause damage, but driving a couple miles down the highway is not going to hurt anything. I've known people to drive halfway across states in 4WD with no problem. My buddy did it with my jeep years ago, and it is still working. There was alot of snow and ice in places (Wyoming in January), but alot of dry pavement too. I would not drive more than a 1/2 mile locked in during normal driving, but in bad weather when ice MAY be present, I would not hesitate to use the 4wd I paid for.
Sign In or Register to comment.

Helpful Tools

Most popular vehicles