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Toyota 4WD systems explained

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  • hicairahicaira 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 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.
  • 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 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_ 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 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_ 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 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
  • 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 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 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 Posts: 305
    I bet your friend backed up sometimes during the time he had the SUV!
  • drew_drew_ 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 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 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 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 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 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 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 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 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 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 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 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 Posts: 10,109
    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 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 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.
  • 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 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 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

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