Wwest, Excellent choice for future on your conversions. Kudo's for that.
I personnally don't believe studded tires are needed most places either and actually hurt traction in many conditions which is why I don't normally recommend them to anyone. I don't know which part of the country your in but for those inquiring on benefits of snow tires and drive options they are obviously in an area that they have a concern and should be addressed as such not just works what works best for you in your area. The guy in FL. doesn't care much of anything about this whole thng unless he has to take a trip way north mid winter.
I also don't consider winter tires to be a band-aid for a non existent wound. I consider them more like Mechanix gloves, Goretex clothing, etc. Enough skinned knuckles and sudden rains and better to be prepared ahead of time to prevent problems. When I used to go out and it's 0 degrees and I had my all season tires on that rode like solid rubber and slid on dry corners it was time for other options. Toss the endless flurries into it and anyone would be crazy to do different (which is why most cars in the area had winter tires on it).
First- Steve if you want to move parts or all no problem. Hopefully done real son.
Second-Wwest, Your area is listed as a milder climate with little snow. When it does it doesn't stay around very long, not much below freezing temps. What works for you in your area doesn't relate to those who get a lot of snow that stays for months so you should help them respectively not just preach your ideal.
By that measure "The guy in Fl (Al, MS, etc.)" should always run on winter tires.
Another RIDICULOUS, uninformative, useless comment that is just typical of many of your posts. Not cold, no snow, no need. Proper info for those in the area they are asking for help on.
As MANY stated prior. "let's agree to disagree" trying to provide proper information with somebody like you is futile.
By the way, Thanks Steve! Hopefully others reading these threads will put all of mine and WWEST's comments into proper perspective. Maybe some of my links will provide useful info for them as opposed to "summer tires with no siping will always provide better traction even on pure ice" :confuse: that others provide.
Sands1, If you read back in this thread you will gain some valuable info for the different systems (and some not so, actually more confusing). You really need to decide more on what fits your need. A larger, heavier SUV has advantages at times (if you need towing capability, off road ability, extra mass to hopefully protect you in an accident) and many cons (extra weight for poor fuel economy, on snow/ice once out of control a lot more mass to try and regain control, parking, High center of gravity = greater rollover risk, plus others).
Most manufacturers will describe their systems as this: AWD (all wheel drive)- the center differential (or something similar) does NOT lock and allows the front axle/wheels to move at a different speed from the rear axle/wheels. This allows you to use it in all conditions (dry, wet, snow, mud) and normally at all speeds. All of them have a different percentage for how much torque is applied to which axle and at what times. All wheels have an opportunity to provide traction but limited to how the front and rear differentials decide which side gets power. some use limited slip that utilize clutch packs that heat up as one wheel spins and start to transfer torque to the other wheel to help gain traction, others utilize the ABS system to apply brakes to only the spinning wheel for the same reason, some have mechanical methods that lock the 2 sides together once one spins, some of the new jeeps control all the differentials electronically and can vary anywhere in between based on sensor input.
4WD (four wheel drive) the center differential or transfer case LOCKS and links the front and rear axles together. Since locked both receive the same amount of torque. Still limited to which wheel gets power based on the same front and rear differential info from above. Having the front axle locked to the rear requires that the tires be allowed to slip on a lower friction surface (snow/ice/mud/gravel) when you go around turns. On dry road and sharper turns (parking lots etc.) the surface has a high friction and does not let them slip. The whole driveline binds up until something gives (which will probably be a very expensive of the driveline). Most of the 4WD systems also have a low range gear option as part of the transfer case to allow those that have the need, the ability to provide a LOT more torque to the wheels for off road, towing heavy things, getting things unstuck (provided your tires have enough of a traction surface)
2WD, FWD, RWD drive only one of the axles and still limited to which wheel on that particular axle gets power based on the differential on that axle.
By the way the Sequoia has all of the above. Rear wheel drive normally, all wheel drive (because the center differential has an option of whether you decide to lock or not) and 4WD when you decide to lock the center diff and a separate transfer case that provides a low range gear. I do not know what the GX470 has for options but should be listed on the websites and/or go check at dealer. Another option to check is Subaru. They have a great proven history for their full time AWD drive systems, some (Forester, Outback) have more ground clearance than regular cars and better than some SUV's, and have pretty good room while getting very good fuel mileage. Only downside is if you need towing capacity for trailers or boats.
You had alluded to being prepared for sudden rains by having winter tires and I have been on FL (AL, MS, LA, etc.) interstates with "sudden rains" where hydroplaning was clearly the rule.
The Daytona 24 hour race was halted in 2004 due to HEAVY rainfall after Paul Newman spun out three times in a row in the exact same spot.
You had alluded to being prepared for sudden rains by having winter tires and I have been on FL (AL, MS, LA, etc.) interstates with "sudden rains" where hydroplaning was clearly the rule.
Do you mean this comment from #1870 "I also don't consider winter tires to be a band-aid for a non existent wound. I consider them more like Mechanix gloves, Goretex clothing, etc. Enough skinned knuckles and sudden rains and better to be prepared ahead of time to prevent problems."
Mechanix gloves for the skinned knuckles, Goretex clothing/jackets for the sudden rains! Winter tires for the consistent cold with snow/ice in my area that lasts for months. Not Winter tires for rain in the south, winter tires to be prepared for snow/ice that accumulates here during WINTER while I'm at work and need to get home, or sleeping/woken up at 3AM, 5 degrees outside, and need to get to the firehouse to drive the ambulance for the fool that wrapped his summer tire equipped car around a tree with an inch of a snow on the ground.
I have searched through all the postings and still cannot find an answer to how to switch into 4WD on my 2005 Highlander. I have read through the owners manual and even it doesn't do justice to describing 4WD. So my question is, how does 4WD work/kick in on a Toyota Highlander? Do I have to do something to switch it to 4WD or does it somehow do it automatically? Thank you. Mike.
The 4WD HL has a full-time 4WD system, meaning it's always in 4WD; there's no way to switch it out of 4WD mode. It's designed for the non-sophisticated four-wheeler who just wants good traction in snow and perhaps does some light off-roading occasionally. But if you feel you need it, buy a replacement switch from an auto parts store for a 4WD vehicle that allows switching between 2WD and 4WD modes, and glue it somewhere in the HL's instrument cluster so your friends will think your HL can switch between 2WD and 4WD. You can even pretend to switch it and tell your friends that it shifts very smoothly between 2WD and 4WD, and ask them whether they can feel it shift...
The 4WD HL is actually a FWD vehicle unless you encounter a circumstance where the front wheels (both) develop some roadslip/wheelspin. When both front tires lose traction with the roadbed while under engine driving torque that will result in the brakes being applied to the slipping/spinning wheels and that will quickly re-route engine torque to the rear via the open center differential. Meantime the engine will have been almost completely dethrottled to prevent further wheelslip/spin which would require even more braking.
Face it, you own a FWD, 2 drive wheels ONLY vehicle.
Near as I can tell, my 4X4 will only drive 2 wheels at a time too unless I kick in the rear locker. So I guess I have a 2 wheel drive also. An all wheel drive will drive all 4 tires depending on the traction just as a 4X4 will. It may be at a different speed depending on the model, but they do all drive. I know my AWD Astro will go everywhere my 4X4 will (minus the locker) traction wise. I run into ground clearance and approach/departure problems of course though. In fact, if I were to strap the 2 together back to back on a ice patch, the Astro may win.
Wwest, The Highlander now has 3 open differentials since doing away with the VC center diff for the 2004 model year. It sends the same amount of power to all 4 wheels until a wheel slips, traction control brakes that wheel or wheels. Until 2004 toyota used a VC center differential and they say it sent power 50/50 front and rear. If you did not get VSC which was not standard until 2005, the rear differential was a Torsen. I have not read anywhere that the Highlander was Front bias. The most that the VC would be is probably 55/45. It is now 50/50 with just an open diff in the center. Open differentials are not bias front or rear.
The HL and RX's three open differentials only provide equal driving torque at a constant speed and with roughly equal traction for all four tires. In order to bias the engine torque to the front, 90/10 F/R, during acceleration they both use differing final drive ratios in the front vs the rear.
That makes the front tires much more likely to slip, spin, first and then braking is used to "force" engine torque to the rear. Note that both front tires must slip in order for this to happen since with only one slipping the virtual front LSD comes into play, only the slipping front wheel is braked, forcing torque to the opposite side.
Obviously if this braking were to continue for an extended period with the engine output fairly high the brake rotors would quickly overheat. So at the initial onset of Trac (AWD mode) braking the engine is also quickly dethrottled.
Like the Trac system on my 1992 LS400, in most cases you can make more headway turning these systems off and managing the gas pedal in a more sensitive way. But be sure and learn where the 60 Amp ABS pumpmotor fuse is in preparation for the day you will need to remove it to get unstuck or continue forward movement up a slightly slippery incline.
I cannot predictably enage 4wd on my 2002 sequoia. I press the 4wd button- the 4 green light come on and the amber light flahes. Some times for up to almost a mile. Other times just a few seconds.
I read the post about tapping the brakes to get it to engage. That works somtimes.
My big concern in that when I start out my long hilly drive in the morning (if there is heavy snow) I won't be able to get into 4wd.
Do others have similar symptoms - or hints? Maybe shifting to neutral ?
Are your tires worn more on front or back? This can cause issues with it locking in, also a good reason to stay on top of the tire rotations.
That said, I have had issues while driving and you need to engage it then slow down some. YES, you can use neutral while in your driveway. The way I do it and have never had an issue with it not engaging instantly is, start the truck place in drive, engage 4WD, place in neutral then back to drive. I forget if it engages when I go to neutral or back to drive but it always was engaged when I started to drive.
My 2003 4Runner also takes forever to lock into 4WD, so now I leave it there all the time in the unlocked mode. My 4WD next to never engaged while not moving, and usually took a 1/4 mile or so to lock in while moving. Summation = STUCK. There's been plenty of past posts regarding the same issue. My 4Runner takes much longer to lock in than former Chevy's and Fords ever did.
IMO, if you even think you'll need 4WD, have it locked in before you need it.
I did some more research on this and this is what I found. The front has a higher final ratio 3.27, the rear is 2.92, but the right front axle connects to the transfer unit which connects the propeller shaft for the rear. They are all driven the same speed because, the ring gear overdrives the pinion gear in the transfer unit. It is very confusing to explain, but all wheels receive equal power until a wheel or wheels slip, then trac steps in and corrects it. I think the different ratios are because of packaging, trying to fit everything. There are a lot of different things going on under the vehicle. The gear reduction evens it out so that each wheel is given equal power.
From discussing this very issue with a lexus factory rep several years ago I was led to believe that the differing final drive ratios F/R was so that under acceleration the front wheels would initially receive the brunt of the engine torque. I was told that only at a constant speed with all four tires having roughly equal traction was the F/R torque distribution 50/50.
I don't see it myself, sound a bit like hocus-pocus, but I was also told, in writing, that the center and front diff'ls are "beefed up" beyond that of the rear diff'l in order to handle the additional drive torque.
And keep in mind that the instant Trac applies the brakes to simulate a partially locked diff'l, front, center, or rear, the engine will also be instantly dethrottled so the brake rotors don't overheat (and later warp) due to continuous use should the engine be left to produce high torque.
Personally I think Toyota and Lexus have now learned a hard lesson and the HL, Sienna, and RX will soon have the RAV4's new AWD system.
And by the way as of the 04 model year the drive ratios are 3.48:1 and 2.92:1 for what it's worth.
The transfer unit drives the front axle and propeller shaft for the rear at .341:1, and that is what equals out the front and rear. If there was no transfer unit to do this, and just an open diff or VC the different ratios would send a lot more power to the front. The service departments in both toyota and lexus in my opinion, have not a clue how their vehicles work. Every time I take my sequoia in for service they take it out of 4WD and tell me it is bad for it. Don't they know it now has the same transfer case as the multi mode 4Runner with a torsen center diff?? I just laugh.
Pardon me, I may be wrong, but I believe your Sequoia has a full time AWD system that uses the brakes for torque apportioning if a wheel slips/spins and in 4WD mode actually locks the center diff'l in which case the service technicians are correct, as much as it really pains me to say so.
You seem to be saying that the transfer unit drives BOTH the front axle and rear drivelines with a common ratio and I don't see how that would "equal out" the differing F/R rear final drive rations.
And I assume by "transfer unit" you mean the gearset from the transmission section into the center diff'l.
The Sequoia has a manual center lock which is not locked when they say this. When in 4WD unlocked mode the torsen center diff splits power same as on the 4Runner. Trac controls both axles. On the Highlander power comes from the transmission to the center differential, then splits left to the front differential, and right to the transfer unit which is a gear unit which drives the front .341 to the rears 1 turn. The transfer unit is after the center differential, actually next to it. The transfer unit connects the front axle and the propeller shaft which drives the rear. It does not matter what the final ratios are because the wheels are turning at the same speed. This means that torque is delivered equal to each axle and wheel until there is wheel slip.This is when trac steps in and slows any spinning wheel. The ratios are different because they have to fit everything, while keeping it compact and lightweight. Three open differentials are used front, center, and rear. Open diffs always send power equal unless there is wheel slip, and then trac makes it equal once again.
Then I guess you need to tell me why, with the right front tire and right rear tire off the ground, I can turn the front wheel one full turn and the rear wheel doesn't.
If you are saying that when you turn the front wheel the rear wheel does not move, try turning the rear wheel and see if the front wheel turns. It won't because of the open differentials. Only the wheel you turn will spin.
Left to right testing in this way if you turn one wheel the opposite wheel will turn an equal distance, maybe in the opposite direction but an equal distance just the same.
Because the front to rear final drive ratios are not equal turning the front wheel exactly 360 degrees will result in the rear wheel turning, again possibly the opposite direction, but plus or minus the ratio difference.
I believe they will turn exactly the same distance. In different directions but the same distance. The transfer unit evens it out. The pinion gear in the transfer unit is smaller than the ring gear, this is what turns the wheels the same speed no matter what the ratios are. Once again the transfer unit does a gear reduction of .341. The rear ratio is 2.929, and the front is 3.27. Add 2.929 and .341 and you get 3.27 the same as the front. The ring gear overdrives the pinion by .341 so they turn exactly the same, with 3 open differentials the power is split equal to each wheel.
All I can say in response is that the difference in rotation distance of the front vs the rear in this test on my 2001 AWD RX300 relates directly to the documented difference in final drive ratios.
I’m not a regular on this forum so I may be asking something fully covered previously; if so I apologize. I’m about to buy a Tacoma 4X4 access cab 4-cylinder (had a 1994 T-100 4X4 that just blew the head gasket.) Here in Texas, VSC comes only as a special order on such a truck, and would come with TRACS and limited slip differential. I’m willing to spend the money to get it, but is it really worth it (reliability, drawbacks)? Is the reduced reliability of a limited slip differential a major issue? I’ll use the vehicle both to commute and for long, often quite rugged and muddy trips in Mexico. Thanks very much for any pointers.
Yeah, 4 cylinder. My 94 T-100 4X4 was underpowered with the old V-6, but that didn't bother me at all; I prefer the good mileage. My main 4X4 use to is to there over extremely bad or muddy roads, not off-roading. (also occasional icy/snowy roads up north.) Many thanks for the advice; VSC is new to me.
I forgot to add: But: if VSC and TRAC could be gotten without the limited slip differential, which would you choose? Reliability is number one for me (and safety).
Sorry, I seem to be an idiot--that last post is unclear. What I am asking is this: IF it were possible to get VSC and TRAC WITOUT also having the automatic limited slip rear differential, would you prefer with or without the limited slip differential? I understand that LSDs are much more finicky and prone to problems than open differentials. (Do they tend to go bad quickly--leave you stranded--or slowly?) Thanks.
There is not an actual limited slip differential with VSC and TRAC, TRAC acts like a limited slip differential. The system works really good. It simply applies brake pressure to the spinning wheel, and cuts back throttle so you can keep or regain control.
VSC is great to save your butt if you start to lose traction and that's part of getting the Sequoia. I would SERIOUSLY prefer a regular LSD to the "auto" LSD as provided by the TRACS system. I hate it in slippery stuff. When encountering mud and snow you often need to keep the wheels spinning some to maintain or get going. The de-throttling and applying brakes to transfer torque on a real slippery hill or middle of mud SUCKS. For the lighter, just a little extra grip it's OK. I've purposely stopped on icy/snowy hills that the Sequoia just wouldn't get moving again on (in 2wd) as there was no throttle available while it tried to figure out how to apply brake and give me power. Even in AWD mode (open center diff TRACS/VSC active) it struggled a lot. Locked the center diff to disable tracs and made it up no problem with some driver induced wheel spin. The same hill in a Chevy Express van with LSD (same tires as Sequoia) stopped same spot on purpose. A little gas, a little slip back and forth from rear end, forward motion all the way up the hill.
TRACS and VSC can be disabled very easily but then you are running a plain open diff with power to the wheel with least traction.
When $$ are available I will be adding a regular mechanical LSD to the Sequoia for those times. On the Sequoia with the center diff locked VSC and TRACS is off anyway and you then have open diffs anyway.
Wwest you are right. Trac is never turned off. I think the VSC is what was holding him back. When he locked the center diff, he said he went right up. The other thing, up until 05 the sequoia had an open center diff, and it needed to be locked more often than it does now with the torsen center diff. I never really need to lock it. As for the Tacoma it is a part time 4WD system, so when you put it into 4WD it locks the center diff, and VSC is disabled. TRAC is still very much active though. In my opinion TRAC by itself works pretty good sending power back and forth.
I read this on the carconnection.com for the new Rav4. It sounds like a real improvement in capability. Does anyone know if this system will allow one wheel to spin when 'locked' into 4WD. ???
"As before, the RAV4 will be available in both front- and four-wheel-drive versions, though a part-time on-demand 4WD system replaces the former full-time viscous-clutch all-wheel-drive system. 4WD versions now have a system that reverts to front-wheel-drive when there are no outstanding traction demands, for the most economical operation, though the system uses an electronic-controlled viscous coupling that sends torque (up to 45 percent) to the back wheels as needed. There's also a 4WD Lock setting that allows a set amount of torque (55/45 front/back) to be sent to all four wheels, up to 25 mph, where the Auto setting overrides it. The RAV4 has never been a serious off-roader, and the 4WD will still offer off-road performance good enough to get owners to most remote campsites and trailheads. Front-wheel-drive models come with a limited-slip differential to help aid grip in limited-traction situations."
Today, I bought a 2003 Tacoma 4x4 SR5 with the the TRD package. The salesman was pretty dense about the specs, and I was wondering how I would be able to tell if this truck was supercharged or not by looking under the hood. This truck is very peppy and I supspect that it is supercharged. However, please help me to confirm this.
My search regarding the new RAV4 on the Toyota Canada web site indicates that side air bags are optional and only on the most expensive model. Toyota Canada does it again! As with the Corolla and Solara, only the rich can get head protection.
Come on Toyota - the Canadian universal health care system is good but not that good, and even if it were, no one yet knows how to unmangle a brain.
What is your message here Toyota? The heads of those who can't muster the extra few thousand loonies are unworthy of protection. Now that is an elitism that I can't stomach.
I was on the prowl for a new vehicle this year and until now, the RAV4 was on my list. No longer! Get with it Toyota!
Now I get your point. I agree with 3 open diffs the gear ratio from the transmission to both the front and rear got to be the same (otherwise the center diff will be over worked, you know what I mean). I was little confused in the beginning since I am used to multiplying the ratios to get the cumulative ratio. (1/3 * 1/6 = 1/18).
Please forgive my ignorance, but could someone please explain how the ECT Snow mode on the '06 Highlander is used? The owner's book gives very little on it and I get the impression from reading it that it is only used for starting up in the snow. Thank you. Mike.
If the information my salesman gave me on my 05 is correct, then it starts the car out in second gear instead of first to try and combat some of the wheel spin that the torquey first gear will give in snow and ice conditions.
Personally I think Toyota and Lexus have now learned a hard lesson and the HL, Sienna, and RX will soon have the RAV4's new AWD system.
I'm not sure what hard lesson you are referring to. I thought the hard lesson was learned before the 2004 model; i.e. the reaction time of VC system . . . hence the open differential solution that comes with RX and Highlander of 2004 vintage or later. Not sure what's so great about the new RAV4 system; isn't "OnDemand" just a market-speak for "low-cost"? What is the reaction time for it? AFAIK, the MDX OnDemand system exhibits significant delay; that's why I got the 04 Highlander.
Via an electromatic clutch pack the new RAV4 will distribute engine torque to the rear, 55/45 F/R, without having to dethrottle the engine to prevent brake rotor overheating.
I think Toyota has gone for the new electronic clutch in 2006 RAV4 to get higher mileage especially now that 2006 model is big. IMHO it is just an SAWD (sometimes AWD). Hope other Toyota models don't follow the suit.
AFAIK, none of the clutch pack solutions ever tried last very long (Subaru automatics, early MB 4matics, MDX, Isuzu TOD etc.); about 60k miles, and that's about it. Most of them also have reaction time issues. I thought that was why MB went open differential with ML320, and so did the current generation Landcruiser, Hummer etc.. It's a lot less expensive and preticable replacing brake rotors than suddenly finding out one day that the normally 90/10 clutch pack is slipping and unable to go into 54/44 mode, in a slippery curve bend.
Dethrottling is something the Vehicle Stability Control program would do any way under slippery conditions.
Comments
Excellent choice for future on your conversions. Kudo's for that.
I personnally don't believe studded tires are needed most places either and actually hurt traction in many conditions which is why I don't normally recommend them to anyone. I don't know which part of the country your in but for those inquiring on benefits of snow tires and drive options they are obviously in an area that they have a concern and should be addressed as such not just works what works best for you in your area. The guy in FL. doesn't care much of anything about this whole thng unless he has to take a trip way north mid winter.
I also don't consider winter tires to be a band-aid for a non existent wound. I consider them more like Mechanix gloves, Goretex clothing, etc. Enough skinned knuckles and sudden rains and better to be prepared ahead of time to prevent problems. When I used to go out and it's 0 degrees and I had my all season tires on that rode like solid rubber and slid on dry corners it was time for other options. Toss the endless flurries into it and anyone would be crazy to do different (which is why most cars in the area had winter tires on it).
Steve, Host
"...sudden rains and better be prepared..."
By that measure "The guy in Fl (Al, MS, etc.)" should always run on winter tires.
Second-Wwest,
Your area is listed as a milder climate with little snow. When it does it doesn't stay around very long, not much below freezing temps. What works for you in your area doesn't relate to those who get a lot of snow that stays for months so you should help them respectively not just preach your ideal.
By that measure "The guy in Fl (Al, MS, etc.)" should always run on winter tires.
Another RIDICULOUS, uninformative, useless comment that is just typical of many of your posts. Not cold, no snow, no need. Proper info for those in the area they are asking for help on.
As MANY stated prior. "let's agree to disagree" trying to provide proper information with somebody like you is futile.
By the way, Thanks Steve! Hopefully others reading these threads will put all of mine and WWEST's comments into proper perspective. Maybe some of my links will provide useful info for them as opposed to "summer tires with no siping will always provide better traction even on pure ice" :confuse: that others provide.
If you read back in this thread you will gain some valuable info for the different systems (and some not so, actually more confusing). You really need to decide more on what fits your need. A larger, heavier SUV has advantages at times (if you need towing capability, off road ability, extra mass to hopefully protect you in an accident) and many cons (extra weight for poor fuel economy, on snow/ice once out of control a lot more mass to try and regain control, parking, High center of gravity = greater rollover risk, plus others).
Most manufacturers will describe their systems as this:
AWD (all wheel drive)- the center differential (or something similar) does NOT lock and allows the front axle/wheels to move at a different speed from the rear axle/wheels. This allows you to use it in all conditions (dry, wet, snow, mud) and normally at all speeds. All of them have a different percentage for how much torque is applied to which axle and at what times. All wheels have an opportunity to provide traction but limited to how the front and rear differentials decide which side gets power. some use limited slip that utilize clutch packs that heat up as one wheel spins and start to transfer torque to the other wheel to help gain traction, others utilize the ABS system to apply brakes to only the spinning wheel for the same reason, some have mechanical methods that lock the 2 sides together once one spins, some of the new jeeps control all the differentials electronically and can vary anywhere in between based on sensor input.
4WD (four wheel drive) the center differential or transfer case LOCKS and links the front and rear axles together. Since locked both receive the same amount of torque. Still limited to which wheel gets power based on the same front and rear differential info from above. Having the front axle locked to the rear requires that the tires be allowed to slip on a lower friction surface (snow/ice/mud/gravel) when you go around turns. On dry road and sharper turns (parking lots etc.) the surface has a high friction and does not let them slip. The whole driveline binds up until something gives (which will probably be a very expensive of the driveline). Most of the 4WD systems also have a low range gear option as part of the transfer case to allow those that have the need, the ability to provide a LOT more torque to the wheels for off road, towing heavy things, getting things unstuck (provided your tires have enough of a traction surface)
2WD, FWD, RWD drive only one of the axles and still limited to which wheel on that particular axle gets power based on the differential on that axle.
By the way the Sequoia has all of the above. Rear wheel drive normally, all wheel drive (because the center differential has an option of whether you decide to lock or not) and 4WD when you decide to lock the center diff and a separate transfer case that provides a low range gear. I do not know what the GX470 has for options but should be listed on the websites and/or go check at dealer. Another option to check is Subaru. They have a great proven history for their full time AWD drive systems, some (Forester, Outback) have more ground clearance than regular cars and better than some SUV's, and have pretty good room while getting very good fuel mileage. Only downside is if you need towing capacity for trailers or boats.
You had alluded to being prepared for sudden rains by having winter tires and I have been on FL (AL, MS, LA, etc.) interstates with "sudden rains" where hydroplaning was clearly the rule.
The Daytona 24 hour race was halted in 2004 due to HEAVY rainfall after Paul Newman spun out three times in a row in the exact same spot.
You had alluded to being prepared for sudden rains by having winter tires and I have been on FL (AL, MS, LA, etc.) interstates with "sudden rains" where hydroplaning was clearly the rule.
Do you mean this comment from #1870 "I also don't consider winter tires to be a band-aid for a non existent wound. I consider them more like Mechanix gloves, Goretex clothing, etc. Enough skinned knuckles and sudden rains and better to be prepared ahead of time to prevent problems."
Mechanix gloves for the skinned knuckles, Goretex clothing/jackets for the sudden rains! Winter tires for the consistent cold with snow/ice in my area that lasts for months. Not Winter tires for rain in the south, winter tires to be prepared for snow/ice that accumulates here during WINTER while I'm at work and need to get home, or sleeping/woken up at 3AM, 5 degrees outside, and need to get to the firehouse to drive the ambulance for the fool that wrapped his summer tire equipped car around a tree with an inch of a snow on the ground.
The 4WD HL has a full-time 4WD system, meaning it's always in 4WD; there's no way to switch it out of 4WD mode. It's designed for the non-sophisticated four-wheeler who just wants good traction in snow and perhaps does some light off-roading occasionally. But if you feel you need it, buy a replacement switch from an auto parts store for a 4WD vehicle that allows switching between 2WD and 4WD modes, and glue it somewhere in the HL's instrument cluster so your friends will think your HL can switch between 2WD and 4WD. You can even pretend to switch it and tell your friends that it shifts very smoothly between 2WD and 4WD, and ask them whether they can feel it shift...
The 4WD HL is actually a FWD vehicle unless you encounter a circumstance where the front wheels (both) develop some roadslip/wheelspin. When both front tires lose traction with the roadbed while under engine driving torque that will result in the brakes being applied to the slipping/spinning wheels and that will quickly re-route engine torque to the rear via the open center differential. Meantime the engine will have been almost completely dethrottled to prevent further wheelslip/spin which would require even more braking.
Face it, you own a FWD, 2 drive wheels ONLY vehicle.
tidester, host
Nice layman's summary of the differences between AWD/4WD/2WD. I bet that'll be useful to more than one reader of this board.
That makes the front tires much more likely to slip, spin, first and then braking is used to "force" engine torque to the rear. Note that both front tires must slip in order for this to happen since with only one slipping the virtual front LSD comes into play, only the slipping front wheel is braked, forcing torque to the opposite side.
Obviously if this braking were to continue for an extended period with the engine output fairly high the brake rotors would quickly overheat. So at the initial onset of Trac (AWD mode) braking the engine is also quickly dethrottled.
Like the Trac system on my 1992 LS400, in most cases you can make more headway turning these systems off and managing the gas pedal in a more sensitive way. But be sure and learn where the 60 Amp ABS pumpmotor fuse is in preparation for the day you will need to remove it to get unstuck or continue forward movement up a slightly slippery incline.
I read the post about tapping the brakes to get it to engage. That works somtimes.
My big concern in that when I start out my long hilly drive in the morning (if there is heavy snow) I won't be able to get into 4wd.
Do others have similar symptoms - or hints? Maybe shifting to neutral ?
That said, I have had issues while driving and you need to engage it then slow down some. YES, you can use neutral while in your driveway. The way I do it and have never had an issue with it not engaging instantly is, start the truck place in drive, engage 4WD, place in neutral then back to drive. I forget if it engages when I go to neutral or back to drive but it always was engaged when I started to drive.
IMO, if you even think you'll need 4WD, have it locked in before you need it.
Simply come to a full stop, back up a few yards until the locking diff'l engages, now GO!
I don't see it myself, sound a bit like hocus-pocus, but I was also told, in writing, that the center and front diff'ls are "beefed up" beyond that of the rear diff'l in order to handle the additional drive torque.
And keep in mind that the instant Trac applies the brakes to simulate a partially locked diff'l, front, center, or rear, the engine will also be instantly dethrottled so the brake rotors don't overheat (and later warp) due to continuous use should the engine be left to produce high torque.
Personally I think Toyota and Lexus have now learned a hard lesson and the HL, Sienna, and RX will soon have the RAV4's new AWD system.
And by the way as of the 04 model year the drive ratios are 3.48:1 and 2.92:1 for what it's worth.
You seem to be saying that the transfer unit drives BOTH the front axle and rear drivelines with a common ratio and I don't see how that would "equal out" the differing F/R rear final drive rations.
And I assume by "transfer unit" you mean the gearset from the transmission section into the center diff'l.
On the Highlander power comes from the transmission to the center differential, then splits left to the front differential, and right to the transfer unit which is a gear unit which drives the front .341 to the rears 1 turn. The transfer unit is after the center differential, actually next to it. The transfer unit connects the front axle and the propeller shaft which drives the rear. It does not matter what the final ratios are because the wheels are turning at the same speed. This means that torque is delivered equal to each axle and wheel until there is wheel slip.This is when trac steps in and slows any spinning wheel. The ratios are different because they have to fit everything, while keeping it compact and lightweight. Three open differentials are used front, center, and rear. Open diffs always send power equal unless there is wheel slip, and then trac makes it equal once again.
Because the front to rear final drive ratios are not equal turning the front wheel exactly 360 degrees will result in the rear wheel turning, again possibly the opposite direction, but plus or minus the ratio difference.
The lone fact that you're considering a 4X4 indicates you should op for VSC/Trac.
TRACS and VSC can be disabled very easily but then you are running a plain open diff with power to the wheel with least traction.
When $$ are available I will be adding a regular mechanical LSD to the Sequoia for those times. On the Sequoia with the center diff locked VSC and TRACS is off anyway and you then have open diffs anyway.
And even if you added a mechanical LSD how would you prevent the "virtual" LSD from reacting more quickly?
"As before, the RAV4 will be available in both front- and four-wheel-drive versions, though a part-time on-demand 4WD system replaces the former full-time viscous-clutch all-wheel-drive system. 4WD versions now have a system that reverts to front-wheel-drive when there are no outstanding traction demands, for the most economical operation, though the system uses an electronic-controlled viscous coupling that sends torque (up to 45 percent) to the back wheels as needed. There's also a 4WD Lock setting that allows a set amount of torque (55/45 front/back) to be sent to all four wheels, up to 25 mph, where the Auto setting overrides it. The RAV4 has never been a serious off-roader, and the 4WD will still offer off-road performance good enough to get owners to most remote campsites and trailheads. Front-wheel-drive models come with a limited-slip differential to help aid grip in limited-traction situations."
Come on Toyota - the Canadian universal health care system is good but not that good, and even if it were, no one yet knows how to unmangle a brain.
What is your message here Toyota? The heads of those who can't muster the extra few thousand loonies are unworthy of protection. Now that is an elitism that I can't stomach.
I was on the prowl for a new vehicle this year and until now, the RAV4 was on my list. No longer! Get with it Toyota!
I'm not sure what hard lesson you are referring to. I thought the hard lesson was learned before the 2004 model; i.e. the reaction time of VC system . . . hence the open differential solution that comes with RX and Highlander of 2004 vintage or later. Not sure what's so great about the new RAV4 system; isn't "OnDemand" just a market-speak for "low-cost"? What is the reaction time for it? AFAIK, the MDX OnDemand system exhibits significant delay; that's why I got the 04 Highlander.
Dethrottling is something the Vehicle Stability Control program would do any way under slippery conditions.