"Torsen...will always be a better solution over an open diff'l".
For a center differential? Can it be locked? If not, I don't agree with that statement. If it can, I can't wait to get one. I am checking on the availability of a torsen diff for the front diff of my 99 Landcruiser, which is open.
In general, the locking aspect of the center diff'l, or whatever, is somewhat indepentant of the type of diff'l, transfer case, etc.
For instance, the totally open diff'l in the pre-04 RXes has a VC in parallel, mechanically, with the differential. That open diff'l could have just as well been a torsen, and the VC could have just as well been an electrically actuated clutch.
I agree with you on the button, but remember that Slee off road and to some extent Manafree are Landcruiser oriented only... To get a button to lock the center diff is not hard to do at all, and takes about 4hrs or less on a Sunday afternoon with a fridge full of cold beers, and some electrical know how...
There are two small windows covered by nets on each side of the D pillar just aft the windows. Could anyone kindly told me the purpose of them? Many thanks.
I found this exerpt from another web site, a review of the 1999 Landcruiser, which explains the ABS use in 4WD Lo.
"Equally impressive is the Cruiser's ABS system, which is operational even in low-range 4WD while the center differential is locked. The system is designed to enhance off-road braking performance, allowing ABS control on poor traction surfaces, while avoiding early activation on steep slopes. It does so by determining road conditions according to changes in vehicle acceleration and road roughness. As road roughness increases, ABS influence will decrease. The system also will determine the slope of the road. As the slope increases, ABS influence decreases."
They are some type of vent for the interior. Close your door with the vehicle running and a/c fan on and walk around the back, you can hear air blowing through them. Then, open a door and the sound goes away. It also stops when the windows are open. I think it is because the Landcruiser is so air tight, it would pressurize and explode without proper egress. That's all I know about it.
Doing my homework, research, before placing my X3 order I came across some interesting tidbits that may be helpful to Toyota/Lexus AWD owners.
BMW recommends turning off the DSC, Dynamic Stability Control, during maneuvers such rocking back and forth to get unstuck in a mud "wallow". Turning it off prevents the dethrottling of the engine so one might actually get out of that mud.
On the other hand it also says that in this mode, DSC off, the brake modulation for left/right torque apportioning might result in an automatic "masking out" of the brake application capability to prevent brake overheating due to allowing high rates of wheelspin.
Next year's "feature" for Toyota/Lexus AWD systems?
I just totaled my 2001 4Runner due to a highway-speed accident on a wet road surface. Although by definition I was going too fast since I lost control of the SUV, I'm wondering whether I should have made different choices of 4WD/VSC, given the road conditions, that would possibly have helped me recover control of the vehicle instead of spinning out of control.
Due to the rain, I had engaged 4WD Hi. My VSC was on. The center differential definitely was not locked.
While going down a moderate grade on an interstate with a light rain but a very wet road, my 4Runner's rear began swinging out counterclockwise. I believe I lifted my foot from the accelerator (although it's possible that I didn't change my accelerator pedal position; it's hard to remember) and turned the front wheels into the spin (i.e., to the right).
Basically, the 4Runner just kept rotating around - turning into the spin did absolutely nothing. After spinning 3/4 around the rear of the vehicle slammed into the concrete center divide, I did another full rotation so that the rear hit the divide again, and I ended up nearly facing forward again as I stopped. Thank God I was not harmed in any way in this high-speed accident.
I used to drive in snow and ice conditions as a matter of course and I've successfully recovered more than once from my vehicle's rear swinging out by turning into the spin exactly as I did in my accident. However, I was in a FWD vehicle in those other instances and it did not have VSC.
Did my being in 4WD with VSC engaged help or hurt my recovery efforts in this accident? Looking at some of the earlier postings that describe braking being applied to up to three wheels in slippery conditions has me wondering...
Thanks for your insight. Thanks also to Toyota for making a vehicle in which I crashed so hard that my driver's seatback was bent backwards by the force of my body against it, but in which I was otherwise so protected that I walked away with only a few sore muscles.
he's plain too fast. No VSC or 10 wheel drive will save you if you go 70 mph try to turn too sharp. You have no traction Wet road or dry road. 4500 pounds is a lot of momentum.
Cruise was not on; never in potentially slippery conditions. I have no sense of whether VSC actually did anything wrt throttle or braking. I don't remember the engine doing anything "on its own."
I agree that, by definition (since I crashed), I was going too fast. Of course, up to that point I had been driving with the vehicle fully under control so I suspect I hit a portion of the highway where the water was a little thicker on the road.
I want to correct any notion that I was attempting a turn at highway speed. I was driving straight when the rear end drifted out to my right. The only turning I did was in response to the spin to try to recover control.
I don't believe vehicle safety systems should compensate for every driver error, such as going to fast, but I would like to understand why, when I tried what had always worked previously, it didn't work this time. Thanks.
4500 pound is a lot of weight, maybe your FWD cars are much less. SUVs have a tendency to roll, your wheels may have left ground. Coupled with wet road no traction on maybe all 4 wheels. Too much for the VSC.
between4rnrs, thanks for the interesting post. I'm happy to hear you're not seriously injured. I've experimented with the VSC, ABS, and brake-assist on slick roads, and here's what I think: You got into a very slick patch where you had VERY low traction (hydroplaning, something on the road, etc.) and there was simply nothing the system could do. It's designed to make the most of available traction, but sometimes that isn't enough. Once you got the spin (vehicle rotation) started, there was insufficient traction to stop it.
I think your choice of drivetrain modes and actions in the incident were correct. Maybe braking would have helped, but I suspect not. In previous vehicles I've very occasionally encountered a sudden patch (usually ice or polished snow) of near-zero-friction and even on the flat there was little I could do. In these cases my car began to spin, and only a combination of luck and eventual traction (and just a little skill) saved me from big problems. You do't have to do anything (such as braking or turning) to cause the spin if conditions are slippery enough, and the failure of the system plus your wheel turning to stop the spin would suggest that things really were slippery, at least for a brief time.
There are other possibilities, though. The system should have at least been blinking its yellow dash light at you, and probably beeping to indicate it had lost control. You didn't mention anything like that. Perhaps there was indeed a VSC malfunction.
The system should have been braking the right side wheels (I don't know the precise combination or balance), but you might not have noticed in all the excitement. I've experienced the right-side-only braking and it wasn't terribly dramatic. The de-throttling and throttle response is instant in my experience, so I don't think that was it.
We can all make mistakes from time to time, no matter how careful we are, but sometimes stuff just happens that's outside all reasonable bounds of caution.
First of all Im glad you are OK, i know what it is like, my sister rolled my TLC when we were going into town at about 60mph last april, we came out without a scratch because my TLC was a tank... Glad to hear your 4Runner was a tank too
I have done my own testing in 4Runners TLCs all equiped with atleast VSC and ABS. The Idea of VSC and ABS is to keep the wheels spinning the same speed as the road is passing, ABS is to prevent lock up, VSC is to prevent overspining the tires. You did everything in the situation right, but you should have had you foot still on the throttle, thats why VSC did not do anything noticable... If you would have left it on it would have instantly cut the power to what it should have been to keep the tires spinnign aproxomitly as fast as the road, which is designed for ultimate traction. But since you pulled your foot off the accelerator you did what the system was going to do but you took all power away where as the system would take what was dangerous away. this mostlikly caused the read tires to spen slower than the road thus no traction was created. Applying Brakes in this type of a slide would have possibly rolled your car, the brakes would have gripeed the front and spun the front more out as the center of weight is not and probably rolled depending on the grade. The absolute right thing you could have done was steer into it, keep your foot on the gas, and pray. two of which im sure you were doing. I know how hard it is to react in that situation, ive been in it too many times. But when an SUV nearing 5000 lbs goes Sideways on flat land it takes a skilled driver to recover, going downhill you need a few angels... Anywho glad you OK.
Will apply moderate braking to the front wheel toward the outside of the spin or overstear. If the spin or overstear still continues to the point that the "moment" line of the vehicle is outside the "line" of that outside wheel, then the braking will stop and only then will the engine be dethrottled.
So if the rear is coming around counter-clockwise, then the right front brake will be moderately applied, rapid on and off modulation. If the rear of the car continues to swing out such that more than 50% of the weight/inertia is outside the "line" of that front tire, then the braking is now detrimental to spin recovery and so the VSC will release them.
Back when, or immediately before, the spin began if the Trac system detected rear wheelspin then the Traction control system would have applied rear braking to prevent wheelspin and to maintain traction.
Since about 2000 the Lexus systems were changed, delaying the onset of dethrottling due to wheelspin, to give the driver recovery time, time to lift/feather the throttle if Trac activated due to power.
The other activity wherein VSC is involved is understear, "pushing" and in that case the standard procedure is to apply braking to the rear wheel to the inside of the "turn". In this case dethrottling is also immediately enabled.
It helps to keep in mind that the two primary sensor inputs to the VSC system is the stearing wheel position, "what direction (and how much)does the driver want the vehicle to turn?", and the yaw sensor "which way/direction (and how rapidly)is the vehicle actually turning?"
As long as the two sensors agree then VSC does not come into play.
The Trac system has responsibility for maintaining traction and therefore its primary inputs are the 4 ABS wheelspeed sensors.
there are more sytems than just VSC ABS and Trac. in the 2000 year run VSC (vehicle skid control this is only dethrotleing) was added, A-TRAC was added (Active traction control) And EBD was added, which is what you are talking about EBD is electronic Brake Distribution, thats the program that does the brake work, VSC is only throttle, EBD is only Brakes and A-Trac is the master.
VSC is vehicle stability control and is only involved in yaw, rotational issues, too much, or not enough.
EBD is electronic brake force distribution, sort of a replacement/update on the old mechanical brake pressure front/rear proportioning valve. During braking it monitors braking effects at all wheels and modulates individual wheel braking pressure to equalize overall braking forces.
Trac was simply traction control and now A-trac incorporates LSD capability.
BA is brake assist supposedly to help some of us keep the the brakes applied more adequately in an emergency braking circumstance.
To say one or the other is the master would be like saying the lead programmer did not understand realtime multi-tasking programming.
One can certainly say that ABS, Anti-lock Braking System laid the eggs from which all of these others were "hatched".
The shop manual for my 01 AWD RX300 indicates that for understearing both rear brakes are applied (moderately??) and the engine is dethrottled.
I have become very well familiar that with overstearing the outside front brake is applied.
And if I try to really push it in snow or on ice, turning or straight, the brakes go crazy and if I persist with a heavy throttle foot the engine is dethrottled.
Ive been driving around on paved streets inCampo Grande in Matto Grosso do Sul (state) and Três Lagoas, and in Araçatuba state of São Paulo. I found one other person with a Landcruiser here, its a mimic of mine hahaha, but it has a 4 litre inline 6 turbo diesle from austrailia. it goes but the V-8 has more grunt. Some times I feel like a made the right choice in bringing it, it takes a good driver to miss car eating pot holes, but the LC can rolled its big fat tyres over some of them. Im not sure when i can make it off to venture around in the fields, ive just been out to some survey sites, near the river / damn not very extensive off roading where i would need a spoter. Thanks for asking though.
Hank My manual says and its possible this is a missprint Vehicle SKID control VSC (introduced for 2000) and in my experiance of off roading it acts mutch like my wifes BMW DSC control, which dethrottles the engine. Ill go to the Toyotay site and reread the info on the systems i could be wrong, but then that would make my manual wrong too..
Wow, little did I know that this community would provide such a robust and caring response to my situation and question, and I thank all of you for that. To clean up just a few issues: I honestly can't say whether the VSC lights flashed or not. My brain was zooming along trying to figure out if there was anything else I could do to recover control, and then I was just waiting for what was going to happen next. To address another point, a friend at work who traveled the same route that morning said he saw other vehicles fishtail in that same area, so I take it there was a particularly bad section of road that contributed to my skid. And finally, as you might have guessed from my sign-on (between4rnrs), I intend to get a new 4Runner to replace my totaled vehicle ($17.6k repair estimate: frame bent down 6-8 inches in the back, rear quarter panels and roof buckled, even the hood was misaligned (but the rear doors still open and close!)). As much as I loved my 2001 model, the new version seems better still, and how can I turn away from a vehicle that took all that damage but left me unharmed?
bconroy, the V8 and V6 systems are functionally identical when in the 4WD/AWD modes. The V6 simply has an extra mode which disconnects the front wheels for RWD only. I like this, as the vehicle drives a little better in RWD mode and probably gets a little better mileage.
I don't consider it a big deal, however, and haven't encountered anything that explains why the RWD mode wasn't made available on the V8s. Interestingly, I think you get the highest towing capacity and fastest 0-60 performance in a RWD-only V8.
true that would be faster and get you better gass milage, But lets face it the 4.7 Litre V-8 is pittiful when it comes to power output. 235hp Ford only has a number like that, but then theres the 325ft lbs of torque. But thats not as impressive as it was when it first came out. Reason; now most every 4litre V-8 has a Varible intake and valves which means unlike the LC enigine that was built for torque, you no longer need to build for torque or build for HP (thought was you build for torque lose HP, and visa versa) Now V-8s with less displacement than the LC's 4.7 are putting out 325hp and 330ft lbs of torque. Toyota take note, you dont need to go to a 5.7 litre just learn to improve the 4.7 that you have you could get it to equal output just up the redline, cange components ect ect.
corancher - thanks for the info. I am now seriously considering getting a V6 rather than waiting for the V8. I like the idea of being able to operate in 2-wheel mode and conserving gas. It probably means the V6 may be a little quiter etc. What do you think? I have a V8 on order, but I just don't want to wait until mid-January. And I can't think of anything I could not do with the V6 versus the V8. So thanks again for enlightening me on the real difference in these two systems.
The V8 4Runner has a 7000 lb tow rating and goes 0 to 60 in about 7.5 seconds. The HP number may not be enough to win the urinary olympics around the water cooler, but it sure seems to be perform well enough on the road.
But if you just have to have more horsepower, wait a month or so for the variable-valve version to start shipping.
the truth is the V-8 is faster than the V-6... Not due to horseies under the hood but due more to the 325 ft lbs or twist. Not to mention the V-8 in the 4 Runner has be bummped up in break horse power i think to about 255. Thanks to VVT-i
nedzel, I like the idea of the "urinary olympics!" Lengthy discussions of relative horsepower (or torque) and acceleration seem a bit misplaced for 4000+ lb. vehicles that have less than 500 HP or so. If you want bragging rights for big acceleration, buy a sports car with much lighter weight and a manual transmission.
Not surprisingly, neither plain HP or torque numbers tell the story very well. Chevy bragged about the 270 HP of its new 6 cyl. in the Trailblazer, etc. and yet these vehicles are slower than some lesser-powered equivalents. In the most reliable comparisons of the V6 and (non VVT-i) V8 0-60 times I've seen, they usually come out about even. That makes sense, as the V6 has more horsepower, is lighter, and has a 2WD mode, while the V8 has more torque. Torque is handy (it's generally easier to translate the power of a higher-torque engine into good acceleration) but in the end it's POWER (measured, say, in horsepower or kW and not lb-ft.) that does the work of accelerating a vehicle. Check your physics textbook if you're interested in the details. With perfect transmissions, a 245 HP vehicle would always out-accelerate an otherwise-equivalent 235 HP vehicle.
Money wasn't a factor in my V6/V8 decision, as I could easily afford either one, and actually changed my mind several times over several months. In the end, I drove both types a few times and liked the way the V6 felt and handled. The RWD-only mode and a front end that is 150 lbs lighter probably explain the "feel" element, though the two were pretty close overall, and I liked them both. I'll do some towing, but not enough to need the V8. That's my situation, and others made different choices that they're happy with, too.
As for differences in noise and vibration levels at cruise or while accelerating, I didn't feel or hear much during test drives. I think I may have felt a slight difference (V8 might have been smoother) under heavy acceleration, but it was hard to be sure. The engine sounds under significant acceleration are somewhat *different* but they were equally quiet otherwise and so I suppose that is a matter of taste.
The new V8 should clearly be faster than the V6 because it has both more torque and horsepower, but unless the V8 badge in the grille and/or bragging rights are decisive for buyers, I always recommend testing them both. Drive, drive, drive, and then buy what you like.
I am a new owner of '05 Sequoia 4WD SR5, I tried to read throught all threads in this forum, with so many discussions on Toyota's 4WD system, I am still very confused.
Could someone give me a quick summary on what kind of 4WD system is in '05 Sequoia? can I always engage in the 4HI mode even in high speed driving? would that harm the drivetrain or engine doing so?
OK, I'm new to this whole 4WD thing, so bear with me... Am serious about buying a '05 Tacoma, Double Cab, TRD Sport Package #2. (Have compared/driven the Ford Explorer Sport Trac, and Dodge Dakota - no comparison!) During my test drive last night, the salesman had me stop, shift to neutral, then move into 4WD mode. What happened to "on-the-fly"? He also indicated that turning in 4WD mode would be difficult - ??? What is the difference between part-time, and full-time 4WD?
If it was 4WD high then there should not be a difference. If it is 4WD low then the center diffential will lock in that case you should not have the truck on paved streets. Because the center diffential locked will make all the tires turn at the same speed causing excessive wear on the tires on pavement, but on gravle and ice and mud off road, it will gain tons of traction. If the car has a lever to shift from 4wd Hi and Lov and 2WD then it is not shift on the fly, that is the way most of the toyotas are set up, It is more reliable than pushing a button. Part time usualy runs a 4WD system with a rear or front wheel bais of power. In the tacoma case I would bet a rear wheel. when these wheels start to slip it will engade and send more power to the front wheels. Torsen differntials do this. Locked center differential will elminate this and send 50 fron and 50 rear power. 2WD is 100% rear. 4WD high means that all four have power however, if one wheel looses traction with all the differntials open then all of the power and torque will go to that wheel. I am not sure about the systems that the Tacoma has on it but the Land Cruiser has electronicly activated brakes that will aply the brakes to this wheel and thus reroute the power to other wheels. It will also de-throttle the engine.
" If the car has a lever to shift from 4wd Hi and Lov and 2WD then it is not shift on the fly, that is the way most of the toyotas are set up, It is more reliable than pushing a button."
Wrong!!! Tacomas are and have been shift on the fly at 60mph or below. Lever or electronic.
Please, someone correct me if I'm wrong. I believe Toyota and Lexus have gone to a high traction multi-mode drive system that does not lock the center differential unless the transfer case is shifted into low range.
2WD....is rear drive only
4WD-HI...braking apportioned AWD, brakes are applied to individual slipping wheel(s) to simulate LSDs, front, rear, and center 98and dethrottling to prevent brake over-heating.
4WD-LO...Locked center differential and disabled VSC, Trac, ABS, etc.
So, the salesperson was likely correct, full stop to shift into 4-lo, locked center differential, binding stearing on high traction surfaces.
Not sure about the other vehicles with center diff lock (Sequoia), but LCs (100sereis) allow for 4WD Lo without locking center diff. In the 80 series LC, when you selected 4-Lo the center diff locked, though you could modify this so that you could go in to 4-Lo without locking the center diff.
I missed a point, as steelcruiser pointed out, apparently its possible to be in 4-lo without locking the center diff'l. But also apparently you can only lock the center diff'l in 4-lo.
if your truck has a center diff lock button you can lock it in high and low setting. But the LC (03-05) lock only when in 4low and you select the low gear on the tranny, you can lock the center by pressing the button though. 98-02 did not have this they locked when you shifted into 4low period, because they used a carry-over transmision from the FZJ-80's. The 03-05 TLC saw the new 5 speed transmision.
that more and more, in the near future, we will begin to see most multi-mode driveline systems designed such that they cannot so easily be driven on tractive surfaces, mistakenly or unknowledgeably, with the diff'l locked.
The brake proportioned AWD system is likely more than adequate 99.99% of the time on-road, and having to put it into low range for off road use, locked diff'l, would not be a serious handicap for off-roaders.
I have no doubt that all of the confusion we are seeing about multi-mode drivelines via some of the poster's questions is resulting in one hell of a lot of needless repairs to these systems due to inadvertant misuse.
"I believe Toyota and Lexus have gone to a high traction multi-mode drive system that does not lock the center differential unless the transfer case is shifted into low range." You can lock the center diff on the 2003 4Runner but hitting a button. That also disengages the spin control. You can do this in 4 low or 4 high. I assume this is true for all 4th generation 4Runners.
'03 Sequoia has locking center diff. It can be locked or unlocked in both 4hi and 4lo. When locked VSC and TRAC are disabled. Which also technically brings you back to 2WD since it does not have LSD or true locker diffs, it uses TRAC to apply brakes on the spinning wheel.
In case any of you do not fully understand center differential and its lock, check below explaination:
Center Differential
Rear-wheel-drive cars need a rear differential to power the right and left rear wheels and let them turn at different rates of speed when cornering. Front-wheel-drive cars need a front differential for the same reasons.
Vehicles with full-time or permanenet four-wheel-drive, or with all-wheel drive, require a center differential (or similar device, such as a viscous coupling unit or VCU). In a tight turn, all four wheels travel at different speeds.
A center differential receives power (or more correctly, torque) from the transmission (or transfer box) and sends this torque to the front and rear differentials, while allowing the front and rear wheels to travel at different rates.
Differential Lock
The main disadvantage of an "open" differential is that the usable torque is restricted by the wheel with the least traction. A differential lock literally locks out the differential action and forces torque to be split equally between each wheel (or each axle)for maximum traction. In a rear-wheel drive vehcile, for instance, locking the rear differential locks the left and right rear wheels together so that both receive equal torque.
In a full-time or permanent four-wheel drive wehcile, locking the center differential locks the front and rear drive-shafts together, sending equal torque to the front and rear axles. While locking a differential helps increase traction, it makes steering more difficult on high-traction surfaces because it tends to force the vehcile to travel in a straight line.
Comments
For a center differential? Can it be locked? If not, I don't agree with that statement. If it can, I can't wait to get one. I am checking on the availability of a torsen diff for the front diff of my 99 Landcruiser, which is open.
For instance, the totally open diff'l in the pre-04 RXes has a VC in parallel, mechanically, with the differential. That open diff'l could have just as well been a torsen, and the VC could have just as well been an electrically actuated clutch.
believe me the beers help
"Equally impressive is the Cruiser's ABS system, which is operational even in low-range 4WD while the center differential is locked. The system is designed to enhance off-road braking performance, allowing ABS control on poor traction surfaces, while avoiding early activation on steep slopes. It does so by determining road conditions according to changes in vehicle acceleration and road roughness. As road roughness increases, ABS influence will decrease. The system also will determine the slope of the road. As the slope increases, ABS influence decreases."
BMW recommends turning off the DSC, Dynamic Stability Control, during maneuvers such rocking back and forth to get unstuck in a mud "wallow". Turning it off prevents the dethrottling of the engine so one might actually get out of that mud.
On the other hand it also says that in this mode, DSC off, the brake modulation for left/right torque apportioning might result in an automatic "masking out" of the brake application capability to prevent brake overheating due to allowing high rates of wheelspin.
Next year's "feature" for Toyota/Lexus AWD systems?
Due to the rain, I had engaged 4WD Hi. My VSC was on. The center differential definitely was not locked.
While going down a moderate grade on an interstate with a light rain but a very wet road, my 4Runner's rear began swinging out counterclockwise. I believe I lifted my foot from the accelerator (although it's possible that I didn't change my accelerator pedal position; it's hard to remember) and turned the front wheels into the spin (i.e., to the right).
Basically, the 4Runner just kept rotating around - turning into the spin did absolutely nothing. After spinning 3/4 around the rear of the vehicle slammed into the concrete center divide, I did another full rotation so that the rear hit the divide again, and I ended up nearly facing forward again as I stopped. Thank God I was not harmed in any way in this high-speed accident.
I used to drive in snow and ice conditions as a matter of course and I've successfully recovered more than once from my vehicle's rear swinging out by turning into the spin exactly as I did in my accident. However, I was in a FWD vehicle in those other instances and it did not have VSC.
Did my being in 4WD with VSC engaged help or hurt my recovery efforts in this accident? Looking at some of the earlier postings that describe braking being applied to up to three wheels in slippery conditions has me wondering...
Thanks for your insight. Thanks also to Toyota for making a vehicle in which I crashed so hard that my driver's seatback was bent backwards by the force of my body against it, but in which I was otherwise so protected that I walked away with only a few sore muscles.
Or else the e-throttle(??) and/or VSC wasn't very quick in shutting down the engine...
Or the VSC malfunctioned and after initially applying the right front brake to counteract the inital "spin" and then it never released it.
I want to correct any notion that I was attempting a turn at highway speed. I was driving straight when the rear end drifted out to my right. The only turning I did was in response to the spin to try to recover control.
I don't believe vehicle safety systems should compensate for every driver error, such as going to fast, but I would like to understand why, when I tried what had always worked previously, it didn't work this time. Thanks.
4500 pound is a lot of weight, maybe your FWD cars are much less. SUVs have a tendency to roll, your wheels may have left ground. Coupled with wet road no traction on maybe all 4 wheels. Too much for the VSC.
I think your choice of drivetrain modes and actions in the incident were correct. Maybe braking would have helped, but I suspect not. In previous vehicles I've very occasionally encountered a sudden patch (usually ice or polished snow) of near-zero-friction and even on the flat there was little I could do. In these cases my car began to spin, and only a combination of luck and eventual traction (and just a little skill) saved me from big problems. You do't have to do anything (such as braking or turning) to cause the spin if conditions are slippery enough, and the failure of the system plus your wheel turning to stop the spin would suggest that things really were slippery, at least for a brief time.
There are other possibilities, though. The system should have at least been blinking its yellow dash light at you, and probably beeping to indicate it had lost control. You didn't mention anything like that. Perhaps there was indeed a VSC malfunction.
The system should have been braking the right side wheels (I don't know the precise combination or balance), but you might not have noticed in all the excitement. I've experienced the right-side-only braking and it wasn't terribly dramatic.
The de-throttling and throttle response is instant in my experience, so I don't think that was it.
We can all make mistakes from time to time, no matter how careful we are, but sometimes stuff just happens that's outside all reasonable bounds of caution.
I have done my own testing in 4Runners TLCs all equiped with atleast VSC and ABS. The Idea of VSC and ABS is to keep the wheels spinning the same speed as the road is passing, ABS is to prevent lock up, VSC is to prevent overspining the tires. You did everything in the situation right, but you should have had you foot still on the throttle, thats why VSC did not do anything noticable... If you would have left it on it would have instantly cut the power to what it should have been to keep the tires spinnign aproxomitly as fast as the road, which is designed for ultimate traction. But since you pulled your foot off the accelerator you did what the system was going to do but you took all power away where as the system would take what was dangerous away. this mostlikly caused the read tires to spen slower than the road thus no traction was created. Applying Brakes in this type of a slide would have possibly rolled your car, the brakes would have gripeed the front and spun the front more out as the center of weight is not and probably rolled depending on the grade. The absolute right thing you could have done was steer into it, keep your foot on the gas, and pray. two of which im sure you were doing. I know how hard it is to react in that situation, ive been in it too many times. But when an SUV nearing 5000 lbs goes Sideways on flat land it takes a skilled driver to recover, going downhill you need a few angels... Anywho glad you OK.
Will apply moderate braking to the front wheel toward the outside of the spin or overstear. If the spin or overstear still continues to the point that the "moment" line of the vehicle is outside the "line" of that outside wheel, then the braking will stop and only then will the engine be dethrottled.
So if the rear is coming around counter-clockwise, then the right front brake will be moderately applied, rapid on and off modulation. If the rear of the car continues to swing out such that more than 50% of the weight/inertia is outside the "line" of that front tire, then the braking is now detrimental to spin recovery and so the VSC will release them.
Back when, or immediately before, the spin began if the Trac system detected rear wheelspin then the Traction control system would have applied rear braking to prevent wheelspin and to maintain traction.
Since about 2000 the Lexus systems were changed, delaying the onset of dethrottling due to wheelspin, to give the driver recovery time, time to lift/feather the throttle if Trac activated due to power.
The other activity wherein VSC is involved is understear, "pushing" and in that case the standard procedure is to apply braking to the rear wheel to the inside of the "turn". In this case dethrottling is also immediately enabled.
It helps to keep in mind that the two primary sensor inputs to the VSC system is the stearing wheel position, "what direction (and how much)does the driver want the vehicle to turn?", and the yaw sensor "which way/direction (and how rapidly)is the vehicle actually turning?"
As long as the two sensors agree then VSC does not come into play.
The Trac system has responsibility for maintaining traction and therefore its primary inputs are the 4 ABS wheelspeed sensors.
EBD is electronic brake force distribution, sort of a replacement/update on the old mechanical brake pressure front/rear proportioning valve. During braking it monitors braking effects at all wheels and modulates individual wheel braking pressure to equalize overall braking forces.
Trac was simply traction control and now A-trac incorporates LSD capability.
BA is brake assist supposedly to help some of us keep the the brakes applied more adequately in an emergency braking circumstance.
To say one or the other is the master would be like saying the lead programmer did not understand realtime multi-tasking programming.
One can certainly say that ABS, Anti-lock Braking System laid the eggs from which all of these others were "hatched".
The shop manual for my 01 AWD RX300 indicates that for understearing both rear brakes are applied (moderately??) and the engine is dethrottled.
I have become very well familiar that with overstearing the outside front brake is applied.
And if I try to really push it in snow or on ice, turning or straight, the brakes go crazy and if I persist with a heavy throttle foot the engine is dethrottled.
Hank My manual says and its possible this is a missprint Vehicle SKID control VSC (introduced for 2000) and in my experiance of off roading it acts mutch like my wifes BMW DSC control, which dethrottles the engine. Ill go to the Toyotay site and reread the info on the systems i could be wrong, but then that would make my manual wrong too..
http://www.toyota.com/landcruiser/key_features/star_safety_system- .html
everything you need to know about ABS, TRAC, EBD, BA, and VSC, it even runs through scenarios for you
To clean up just a few issues: I honestly can't say whether the VSC lights flashed or not. My brain was zooming along trying to figure out if there was anything else I could do to recover control, and then I was just waiting for what was going to happen next. To address another point, a friend at work who traveled the same route that morning said he saw other vehicles fishtail in that same area, so I take it there was a particularly bad section of road that contributed to my skid.
And finally, as you might have guessed from my sign-on (between4rnrs), I intend to get a new 4Runner to replace my totaled vehicle ($17.6k repair estimate: frame bent down 6-8 inches in the back, rear quarter panels and roof buckled, even the hood was misaligned (but the rear doors still open and close!)). As much as I loved my 2001 model, the new version seems better still, and how can I turn away from a vehicle that took all that damage but left me unharmed?
thats what i said, and i ended up with a wonderful used 2003 TLC.
Good luck in you search, (note; new 4Runners have more power than the TLC. V-8 runs around 277hp V-6 runs 240.... LC V-8 runns 235... arg...)
BJC
I don't consider it a big deal, however, and haven't encountered anything that explains why the RWD mode wasn't made available on the V8s. Interestingly, I think you get the highest towing capacity and fastest 0-60 performance in a RWD-only V8.
But if you just have to have more horsepower, wait a month or so for the variable-valve version to start shipping.
Not surprisingly, neither plain HP or torque numbers tell the story very well. Chevy bragged about the 270 HP of its new 6 cyl. in the Trailblazer, etc. and yet these vehicles are slower than some lesser-powered equivalents. In the most reliable comparisons of the V6 and (non VVT-i) V8 0-60 times I've seen, they usually come out about even. That makes sense, as the V6 has more horsepower, is lighter, and has a 2WD mode, while the V8 has more torque. Torque is handy (it's generally easier to translate the power of a higher-torque engine into good acceleration) but in the end it's POWER (measured, say, in horsepower or kW and not lb-ft.) that does the work of accelerating a vehicle. Check your physics textbook if you're interested in the details. With perfect transmissions, a 245 HP vehicle would always out-accelerate an otherwise-equivalent 235 HP vehicle.
Money wasn't a factor in my V6/V8 decision, as I could easily afford either one, and actually changed my mind several times over several months. In the end, I drove both types a few times and liked the way the V6 felt and handled. The RWD-only mode and a front end that is 150 lbs lighter probably explain the "feel" element, though the two were pretty close overall, and I liked them both. I'll do some towing, but not enough to need the V8. That's my situation, and others made different choices that they're happy with, too.
As for differences in noise and vibration levels at cruise or while accelerating, I didn't feel or hear much during test drives. I think I may have felt a slight difference (V8 might have been smoother) under heavy acceleration, but it was hard to be sure. The engine sounds under significant acceleration are somewhat *different* but they were equally quiet otherwise and so I suppose that is a matter of taste.
The new V8 should clearly be faster than the V6 because it has both more torque and horsepower, but unless the V8 badge in the grille and/or bragging rights are decisive for buyers, I always recommend testing them both. Drive, drive, drive, and then buy what you like.
I am a new owner of '05 Sequoia 4WD SR5, I tried to read throught all threads in this forum, with so many discussions on Toyota's 4WD system, I am still very confused.
Could someone give me a quick summary on what kind of 4WD system is in '05 Sequoia? can I always engage in the 4HI mode even in high speed driving? would that harm the drivetrain or engine doing so?
Thanks you in advance for any advice!
Thanks!
Wrong!!! Tacomas are and have been shift on the fly at 60mph or below. Lever or electronic.
2WD....is rear drive only
4WD-HI...braking apportioned AWD, brakes are applied to individual slipping wheel(s) to simulate LSDs, front, rear, and center 98and dethrottling to prevent brake over-heating.
4WD-LO...Locked center differential and disabled VSC, Trac, ABS, etc.
So, the salesperson was likely correct, full stop to shift into 4-lo, locked center differential, binding stearing on high traction surfaces.
The brake proportioned AWD system is likely more than adequate 99.99% of the time on-road, and having to put it into low range for off road use, locked diff'l, would not be a serious handicap for off-roaders.
I have no doubt that all of the confusion we are seeing about multi-mode drivelines via some of the poster's questions is resulting in one hell of a lot of needless repairs to these systems due to inadvertant misuse.
http://www.toyota.com/landcruiser/key_features/star_safety_system- .html
Center Differential
Rear-wheel-drive cars need a rear differential to power the right and left rear wheels and let them turn at different rates of speed when cornering. Front-wheel-drive cars need a front differential for the same reasons.
Vehicles with full-time or permanenet four-wheel-drive, or with all-wheel drive, require a center differential (or similar device, such as a viscous coupling unit or VCU). In a tight turn, all four wheels travel at different speeds.
A center differential receives power (or more correctly, torque) from the transmission (or transfer box) and sends this torque to the front and rear differentials, while allowing the front and rear wheels to travel at different rates.
Differential Lock
The main disadvantage of an "open" differential is that the usable torque is restricted by the wheel with the least traction. A differential lock literally locks out the differential action and forces torque to be split equally between each wheel (or each axle)for maximum traction. In a rear-wheel drive vehcile, for instance, locking the rear differential locks the left and right rear wheels together so that both receive equal torque.
In a full-time or permanent four-wheel drive wehcile, locking the center differential locks the front and rear drive-shafts together, sending equal torque to the front and rear axles. While locking a differential helps increase traction, it makes steering more difficult on high-traction surfaces because it tends to force the vehcile to travel in a straight line.