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Toyota 4WD systems explained

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  • I just got a used 99 Toyota 4Runner Limited. It has the push button on the side of the 4wheel drive lever and the ability to put it into 4H and 4L with locking center differentials and locking rear diffs button on the dash. Are you with me there? So I believe it is a full time and a part time system. I do understand why not to drive on dry pavement with LCD or the rear diff engaged. I am 23 years old and this is my first 4x4 or truck. I just wanted to make sure I know my system before I go backcountry driving in Colorado.

     

    Let me know if I am wrong:

    I am cloudy on a few things. I believe when I hit the button that just the front left and the back right wheel have power and if the rear loses traction the front keeps the truck moving and that this is called full time 4w drive. If I shift the lever into 4H with locking center differential, than the front and rear will move at the same speed and not allow the front or back to move faster and this is called part time. Does the 4H with LCD make all four wheels have power or is it just still one in the front and back? Whats the advantage with LCD over just the push button mode (full time)? I have a good idea what the locking rear diff does, it basically gives 50/50 power to both back wheels but I always wonder whats going on with the front at the same time. Do the 2 front wheels ever have power at the same time. For instance lets say that I am in 4L with LCD or 4H with LCD, what wheels truly have power?

     

    Thanks for the help. I am just getting started and I find it interesting but it can be confusing. I want to be confident in my ability to execute the right moves.
  • russlarussla Posts: 74
    Let me know if I am wrong:

    "I believe when I hit the button that just the front left and the back right wheel have power and if the rear loses traction the front keeps the truck moving and that this is called full time 4w drive."

     

    full time means that the center diff is unlocked, and if you have open diffs front and back, then only one wheel will spin, if it looses traction (or if two wheels should both lose traction simultaneously, it is possible to spin both one on the front and back) but if 3 wheels have traction and one doesn't, then only one will spin. and you lose forward propulsion. Left or right isn't a factor, it's the traction (or lack of )that determines which wheel spins first. usually if you're already moving, your momentum may carry you to a different spot where the traction is better and the spinning tire may actually start to get traction

     

    "If I shift the lever into 4H with locking center differential, than the front and rear will move at the same speed and not allow the front or back to move faster and this is called part time."

     

    Yes this is part time, the front driveshaft and rear drive shaft, are now locked together, in the a similiar situation to above, the fronts will keep pulling should you lose traction on one rear tire

     

    "Does the 4H with LCD make all four wheels have power or is it just still one in the front and back? "

     

    all wheels get power (torque) until one loses traction, in Part time, you have to lose traction on the front and on the rear to get stuck (one side, doesn't matter which - if you have open diffs)

     

    "Whats the advantage with LCD over just the push button mode (full time)? "

     

    it guarantees that torque gets to the front and the rear, (full time has an open center diff, so you can get stopped with one wheel slipping

     

    "I have a good idea what the locking rear diff does, it basically gives 50/50 power to both back wheels but I always wonder whats going on with the front at the same time."

     

    Yes, the locking rear diff ensures that both wheels turn at the same rate. They're not getting the same power, because one could be on ice and the other on the road, so the torque or power is applied to the one on the road

     

    "Do the 2 front wheels ever have power at the same time. For instance lets say that I am in 4L with LCD or 4H with LCD, what wheels truly have power? "

     

    in any 4wd setting,(full and part time) where all the tires have traction, the wheels "have power" to use your phrase, the problems arise when one wheel loses traction, a normal diff will send the power, to the wheel with no traction, and the wheel with traction doesn't get any.

     

    these days, there are several systems that deal with this issue, electric locking diffs, Limited slip diffs, viscious couplings (a sort of autolocking center diff) torsens, and wheel braking to create torque transfer (not so good for off road)
  • tlcmantlcman Posts: 220
    wheel braking to create torque transfer (not so good for off road)

     

    It works well off road, but the avid offroader should not rely on these, if you are gettting to a camp site 20 miles in on a dirt road that gets tough some times then you will be fine. But for people like me ARB air lockers are great, to get through mud you can not use te Trac system it will de-throttle the engine and you will get stuck, you need to keep the wheels spining a bit to get through it.
  • Anyone have an opinion whether to get a 1999 or 2000 year Landcruiser regarding the 4wd drivetrain. FYI: This will be used on and off-road; with the emphasis on off-road (gravel, dirt, mud, hills, general off-road travel...but not extreme off-road...not Rubicon!)
  • tlcmantlcman Posts: 220
    Drive train is exactly the same... the change did not come until 2003 when they put a 5 speed in. the drive train in the 1991-2002 is the same four speed. With that said, the only advantage is that the front differential splitter for the IFS is a 4 prong in the 00 rather than a 2 prong in the 98 and 99. It may make it a bit stronger, but i dont notice any differnaces. Any land Cruiser will do great off road, no suprises, theve been doing it for 50+ years

    -Mike
  • With part-time 4-wheel drive, is it advisable to run in 4-wheel mode when conditions are "merely" slippery? That is, on a highway where traffic is moving at, say, 30 mph in a snow or ice storm and the road is lightly covered, am I better or worse off in 4-wheel? Would I lose a modicum of control when lane changing because my front wheels are turning at the same speed?
  • wwestwwest Posts: 10,706
    Many of the newer 4WD systems only allow the diff'l to lock in low range. Good idea IMMHO.
  • Hello all- I realize Xreas is not a 4wd system but thought I would post here because of the other previous good posts. I am currently looking for a 2003 or 2004 4Runner- prefer the V-8 2WD version. I am not crazy about the two-tone plastic on the 03 model (the hood scoop is okay). I really want the Xreas suspension/shock system, and know for sure it is on all Sport models, and a stand-alone options on others. I have been looking at 4Runners on Autotrader and calling dealerships, but many of the salespeople have been clueless as to what X-Reas is, let alone how to tell if one of the vehicles on the lot have the system. To further confuse things, some of these same bright people are labelling 4Runners as SR5/Sport in their ads (ones that clearly don't have a hood scoop in the photos). Is there any other way to visually tell is the car has Xreas as an add-on option? I have noticed looking at the interiors that all Sports (and some non-sport models) have a leather shift knob and leather covered steering wheel and others have a hard plastic. Is this the clue I am looking for? Thanks for any input you may have!
  • Thanks russla for the detailed reply. The information is helpful and appreciated. Does anyone have anything to add for a newbie to the 4 wheel drive scene? Any kind of information is appreciated, either specific to my vehicle or knowledge to keep my out of trouble. This coming up summer I am going to do some backcountry driving in Colorado over some mountain passes, just to give you an idea of the terrain I will be cruising. See my first post for additional info.

     

    99 Toyota 4Runner Limited:

    center and rear diff locks and a push button full time mode

     

    Thanks
  • tlcmantlcman Posts: 220
    Hey where are you abouts in Colorado?! I love living there! Anywho, never go out alone, always bring buddys along in other SUVs bring recovery gear, snatch straps and hi lifts a re a good and cheap alternative to a wintch. there is no need to lock your lockers untill you need them or think that you will need them. Do not drive above 10 mph with any of your lockers locked. bring a 12 volt tyre pump in case you have to deflate your tyres for added traction somewhere along the trip.
  • There was a significant change in the '00 vs. the '99 though. A rear locker was an option in '99, but it was dropped in '00 when the electronic traction control was introduced.
  • tlcmantlcman Posts: 220
    true but i didnt mention that because he has a 99 so that info is not relavent to his case, i did not want to confuse him. No offense
  • None taken Mike, but as you can see from his post he's in the market for a '99 or an '00. He doesn''t have one yet

     

    "Anyone have an opinion whether to get a 1999 or 2000 year Landcruiser regarding the 4wd drivetrain. FYI: This will be used on and off-road; with the emphasis on off-road (gravel, dirt, mud, hills, general off-road travel...but not extreme off-road...not Rubicon!)"
  • Very impressed with the level of discussions in this group - hope someone can help me diagnose what I think is a problem. Recently purchased a 2000 SR5 V6 with Auto 4wd, 75K miles. Have noticed occasionally that, when almost stopped after gradual braking a slight rough feel to the brake pedal then a sudden lurch to a stop. When accelerating out of that stop, there's a slight hesitation, a release, then smooth driving.

     It's almost as if there's a clutch mechanism engaging. No pattern - just happens about 2% of the time. Any insight? Thanks for any help.
  • Quote = penobscot: With part-time 4-wheel drive, is it advisable to run in 4-wheel mode when conditions are "merely" slippery? That is, on a highway where traffic is moving at, say, 30 mph in a snow or ice storm and the road is lightly covered, am I better or worse off in 4-wheel?

     

    It is my habit to put my Tacoma 4WD into 4WD high range when there is ice and snow on the highway. In places where there is alternating icy/wet areas, I'll still keep it in 4WD, as long as there is more ice than areas free of ice.

     

    There will be no damage to the system as long as you are not turning sharply on pavement with a high cohesion (i.e. no ice), and that all four of your tires are the same size.

     

    I've lived in snowy areas for more than 30 years and have never encountered drivetrain damage from this practice with any of my 4WD vehicles.
  • wwestwwest Posts: 10,706
    Please realize that isn't likely to happen so don't drive over too many dry spots in part time mode.

     

    Four brand new tires and equally inflatted, maybe.
  • The Sequoia has traction control to help get you going in slippery conditions and VSC to help straighten you out when your going sideways. The Sequoia has an open diff, the traction control applies brakes to the spinning wheel to send torque to the other. I was out playing on some steeper snowy/icy hills in 2wd to see how effective it all is. I had the system extremely freaked out to where it pretty much cut all my throttle and I was sliding backwards, trying to go forward. Yeah I got myself out with no issue in 4wd but wasn't happy. I tried the same exact hill and spot in my Dads Chevy Express Van that has an LSD and was able to make it up with just some spinning and a little side to side slide action (You know the fun fish tale kind). Having power delivered to both wheels instead of brake to one and power to other is always a better choice in my opinion in those real slippery conditions (yes I know the disadvantages of accelerating in a turn in slippery conditions also).

     

    My question is what effect will adding a rear LSD have on the VSC system? VSC is disabled when you put in 4WD and lock the center diff since it can't apply brakes independently with power to at least one wheel on each axle (front and back). But If I have the center diff unlocked or I'm in 2WD what will happen? I'm stepping on the gas in 2WD and hit some gravel/mud/snow/ice and rear starts to swing out. The yaw sensors and everything else VSC etc. say HEY apply right rear brake only to make him straight. The new "mechanical" lsd says YO one wheel is spinning and the other is slowing down make those clutches grab tighter to put more power to that wheel that's going too slow. What will this do to the whole system? Clutch packs in LSD burn up? Brakes heat up and wear? ABS pump over heats? Throttle shuts off making spinning wheels null and void?

     

    I know all the positive aspects of VSC and Trac and VSC will probably save MANY lives from stupidity accidents. I just HATE when I lose control over giving the truck throttle. Yes I know all of wwest's posts about letting off the throttle right away but off road/mud/snow/gravel/ice/steep hill are not always the best time to lose momentum or power to the drive wheels. A little extra spin of the tires to clear the sticky mud or snow from tread provides a new "clean" biting surface.
  • wwestwwest Posts: 10,706
    the best system allows the (4WD experienced/educated) driver to switch off VSC/Trac.

     

    I have educated myself as to where, exactly, the ABS pumpmotor fuse is on my 2001 AWD RX300 just in case.

     

    You can switch the Porsche PSM system off but it will come back on automatically if you get on the brakes, seems as close to a perfect VSC system as one can get.
  • 2toyotas2toyotas Posts: 104
    I don't think the two could work together. Traction control never turns off. When the Sequoia is in 4wd the traction control only brakes the spinning wheels, it does not cut power like in 2wd. I think the best way to tackle that incline would have been with light throttle so it would not cut engine power. I think the system works more like a LSD when in 4wd. I had an 03 and now have an 05, Toyota added a Torsen center differential for 05, and I can definitely tell the difference. The traction control does not engage as much, and only works side to side on each axle not front to back which makes front to back power changes more seamless and smooth. I do think that both systems are pretty amazing though. I had a Hummer H2 for a week last winter and it was all over the road in slippery conditions. I could not wait to bring it back, it did not come close to my Sequoia or 4Runner in bad weather.
  • joharajohara Posts: 1
    Russla,

     

    Great explanation on the 4WD drive system.

     

    I have a question for you re rear locking differentials. I have a 2005 SR5 4Runner with the V6. I only have a CDL, do you know if it's possible to install a rear locking differential? I don't plan on putting one up front, so I'd like to go the Toyota route instead of the ARB.

     

    Incidentally, the new 4Runner replaces a Land Rover Discovery II (maintenance money pit). The Disco allowed you to lock the center diff without disabling ETC, (their version of the ABS torque-transferring technology) In an unplowed parking lot with about 8" of snow in it, I found that the 4Runner does better with VSC enabled than the Discovery did with ETC only. But that the Discovery did better with ETC and the CDL that the 4Runner did with the CDL, probably because VSC is disabled at that point.

     

    My ideal setup would be VSC for most of the time while offroading (NJ Pine Barrens, mostly sand & mud) with the ability to lock up the center and rear differentials before hitting the rough spots. (3-wheel drive, essentially)

     

    Thanks in advance for any information you can offer.

     

    Jim
  • i just picked up a used 2002 4runner sr5 that did not have a manual with it. Just wanted to make sure i was using the 4wd system correctly. I have a H N L setting and was aware of turning on the button. Is the system automatically in high or do i need to shift into it after turning the 4wd on?

    thanks for your help

    jane
  • I have a new 05 Sequoia with only 500 miles on it. The dealer is having to replace the rear differential. Two Questions

    1) What are the long term problems that will manifest itself after doing this?

     

    2) How should I test drive it when I get it back from the dealership?
  • tlcmantlcman Posts: 220
    1) Depends on what happend, mostlikly i would expect 0 Problems, but if it was casue because of improper drive train set up which is unlikly then there could be other problems. But it was most likly a bad component, dont worry about it.

    2)Regular Check ups will be fine
  • evsevs Posts: 6
    Can anyone tell me why my 05 tacoma binds up in turns while in 4wd and my wifes 01 land cruiser, which is in AWD all the time never binds up in turns. Why don't they make 4wd that doesn't bind up in turns? Also if our land cruiser can go anywere in AWD why is that system not incorporated into 4wd pickups so there is no binding while turning. Any help would be greatly appriciated. Thanks, EVSDOG
  • Go back and read the very first posts in this forum.
  • wwestwwest Posts: 10,706
    4WD has a locked center differential which REQUIRES that the front driveline and the rear driveline ALWAYS rotate at exact the SAME rate. In a turn the front wheels take a different path than the rear and this will result in differing turn rotating for the dront driveline vs the rear rear.

     

    AS a result something must "give", in most cases resulting in intermittent tire scrubbing or slipping to relieve the driveline "windup".

     

    AWD, instead of having the center differential fully, "hard" locked, often adds a form of "rubber band", or partially, "softly", locks the center differential.
  • tlcmantlcman Posts: 220
    your LC will do what the tacoma does if you drive with the center differential locked.
  • I have a 1999 SR5 4 runner with 5-speed and 4WD.
    Here is my question. The SR5 comes with a stick to engage the 4WD (if you have a manual tranny) into 4L , 4H whatever you want.

    Now, the LTD version also has a button on the dash that when pressed supposedly locks out the rr diff and makes it such that you would only drive with this feature on if you were off-road and going fairly slowly.

    My question is: If i don't have that button option, then when I engage the 4wd, is it ALSO locking the rear diff to the maximum 4wd and therefore I too should not exceed that 15 mph speed and not drive as such on the pavement? In other words, If the LTD engages 4wd, BUT, driver decideds not to engage the button, can he drive it on the freeway at 55 in pouring rain like an AWD, but with my setup, I am precluded from that feature?

    No one, including toyota, can answer that question for me. What is the difference in the "two levels" of 4wd on the LTD and which "level" do I get on my SR5 when I engage it?

    thanks
  • russlarussla Posts: 74
    sorry haven't been here in a while,

    "is it possible to install a rear locking diff?

    Yes, generally,

    but I don't know about 05's specifically, If it's available as an option, then one could conceivably get the Toyota parts and install them in their rig.

    Regards
  • tlcmantlcman Posts: 220
    4WD high and low only changes the gearing of your rig. i am not particularly familiar with Tacomas but I will give you my best. If your switch from 2WD to 4WD you suposivly can still safely drive your truck upto and beyond 55mph (but if you are going that fast you dont even need it) However, with my Land Curiser the Center differential is Unlocked meaning that no binding will occour in the drive train, yours will engage from what i have herd meaning that driving through a turn in 4WD will be different than going in 2WD. LSD not LTD (limited Slip Differential) is not used on Toyotas (minus a viscious coupler on a Rav4 or highlander) Anyway, those who have the rear differential locker option will have the dial in their truck if their is no dial you dont have the locker. Same as Land cruisers. When you shift into 4WD or 4WD low you will have your center diff locked meaning power 50/50 front and rear, the system (according to Land Cruisers and I suspect its the same for Tacomas) will not lock your rear locker. This is for you to decide. If you do have the locker and decide to lock it there will be a dash light that says Rear DIFF and will be orange or red it will flash until the unit locks then it will stay on solid. The same goes for your center diff (according to the LC) If your in 4WD high you can go above 55mph (hence the gears being spaced farther than the LOW)

    In short; you dont have the dial you dont have the locker. It will not and does not have the ability to lock your rear.
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