Awd On Rx330, Total Hoax?

[Rx330driver]

Now i know that its the 4wd all the time, and that it only kicks in when theres slippage. But has anyone actually seen the indicator, im guesing the one with the car on squiggly lines, turn on on the dash. Earlier on Sunday, it was donwpouring, and i had to brake pretty hard all off a sudden from 60 mph. All i heard was a buzzer, very light sound, and the brake pedal was kinda shaking, im taking it as a sign of slipping, and no warning light what so ever. So do we actually get to see this thing in action? I guess im just curious as to see if any of us has ever had the other two wheels kick in. Oh and what does that buzzer mean...no light, just buzzer. :chairshot:

[arens]

What you just described sounds like the anti-lock brakes kicking in. 4wd and awd have no factor in slowing down.

If you really wanted to test the awd you should find a nice deserted loose dirt/gravel road to test under accelleration.

[bciesq]

Earlier on Sunday, it was donwpouring, and i had to brake pretty hard all off a sudden from 60 mph. All i heard was a buzzer, very light sound, and the brake pedal was kinda shaking, im taking it as a sign of slipping, and no warning light what so ever.

Sounds like a good description of the anti-lock brakes kicking in to me. The sound you heard and the pulsing in the pedal were the brake pads engaging and disengaging rapidly.

From http://auto.howstuffworks.com/anti-lock-brake.htm

When the ABS system is in operation you will feel a pulsing in the brake pedal; this comes from the rapid opening and closing of the valves. Some ABS systems can cycle up to 15 times per second.

[ccw2006rx330]

Yes, During the last snow in the NE. Entering a highway, the on-ramp still had snow on it. As soon as the back end started to slip it kicked in and straightened up immediately. Light "with the car on squiggly lines" came on.

[stonecutter]

Yes, During the last snow in the NE. Entering a highway, the on-ramp still had snow on it. As soon as the back end started to slip it kicked in and straightened up immediately. Light "with the car on squiggly lines" came on.

This and other reactions posted sound more like one or more safety features in action than AWD. A sampling from Lexus's website:

ABS, EBD (electronic brake distribution), VSC (vehicle stability control), TRAC (traction control)

http://www.lexus.com/models/rx/safety.html#stability

That still does not answer the original question, of course, I'm also curious, how DOES one know if the AWD is working ?

[wwest]

What I have discovered in my 2001 AWD is that at the moment of VSC activation I am generally too involved in driving the vehicle to look down at the instrument panel when/as the buzzer sounds. And then by the time I do the "event" is over and there is no indication. I'm relatively sure that at least two or three of the incidents involved understearing so I have concluded that the "squiggly" light comes on with the buzzer but doesn't remain on long enough for the driver to take notice.

But to answer you base question...

Yes, the RX series is AWD/(4WD) for marketing purposes only.

The initial series was natively front torque biased, 95/5 and has a viscous clutch/coupling mounted across the two outputs of the center differential. The idea was that with slippage at the front the VC would tighten up and partially lock the center differential and thereby raise the torque level to the rear.

The problem was that the formulation of the viscous fluid was such that it remained flaccid and even if front wheel slippage persisted for an extended period would only couple about 25% of the engine torque to the rear. So in the short term, matters of seconds, it had no drive toque to the rear.

In 2004 the VC was dropped, center differential always fully "open" in favor of the use of braking to apportion engine torque front to rear and side to side. In effect the brakes are used to simulate LSDs. Limited Slip Differentials, front, center, and rear. For some reason the torque biasing to the front was also increased in 2004.

The problem with that was that while you had virtually instantaneous torque apportionment from the front to the rear if the slippage persisted the engine had to be dethrottled to prevent the brake rotors from overheating and warping. Not just a few owners were at their wits end trying to figure out how to disable the system so wheelspin, or back and forth rocking, could be used to get unstuck.

Now I see that for the new RX350 the VC is back in use.

Hopefully with a better viscous fluid formulation and an improved method of quickly dispersing the HEAT from the VC once the "event" has passed. And maybe, just maybe, the engine torque is now biased to the rear as it should be, but I wouldn't put money on that.

Try, try, and try again, Toyota will get it right sooner or later.

In the mean time I'm off to see Acura about purchasing the new RDX as soon as it is available. Dynamic, on-the-fly, torque allocation, 70% to the rear if conditions warrant and as much as 100% of that to the outside rear wheel while turning.

Sooner or later the RX series will get the new DFI engine and the absolutely STELLAR GS & IS AWD system. Hopefully sooner rather than later, meantime I'll be enjoying my RDX.

[Rx330driver]

Haha, im glad people agree with me that the AWD is a hoax. thanks guys, so i gues it is anti lock brakes...very interesting, good thing i had the pads changed last week. so, to just sum it up, you do hear a buzzer when the anti lock brakes kick in. :whistles:

[mehullica]

I've been 4 wheeling in a 2001 Rx300, and it works. AWD, not a hoax.

[cantsleepnk]

AWD is not a hoax and it is full time 50:50 despite what others have said here. It doeasn't just kick in when there is slippage but It's on all the time.

Why would Lexus cheat and lie to it's customers and the whole world if it was actually 95:5 or if it was only part time ???

[Rx330driver]

*gives confused look*. Can someone who happens to own both an AWD rx330 and one of those lifters, lift the car up and gas it. that would be appreciated, lol, just to solve this whole dispute. Im not saying its a hoax, but it is rarely every used...therefore being almost useless to have.

[wwest]

*gives confused look*. Can someone who happens to own both an AWD rx330 and one of those lifters, lift the car up and gas it. that would be appreciated, lol, just to solve this whole dispute. Im not saying its a hoax, but it is rarely every used...therefore being almost useless to have.

Been there, done that.

I traded up from a MY2000 AWD RX300 to a MY2001 AWD RX300 mostly to get the HID headlamps and the new VSC/Trac system. I had begun to suspect that my 2000 wasn't really AWD and this had been verified partially by Lexus informing me that it was fornt biased 70/30.

I'm old enough that my color night vision is fading and the HID does help.

I was told that the rear LSD option had been dropped in favor of brake apportioning being used to prevent wheelslip/spin in the front or the rear, "virtual" LSDs in effect. That turned out to be true and I suspect that also works front to rear even on my 2001.

By happenstance I ended up driving down a very wet and muddy lane to a friend's house and when I tried out the AWD by trying to accelerate I didn't get the same "feel" of AWD an I had in my previous two Jeeps, and 85 and a 92, both with 2WD, AWD(??), & 4X4. 4X4 low also which I never used.

So I came home and put the RX up on four jackstands and discovered that there was virtually no drive to the rear wheels. To verify that I placed a 1x2 light pine board through each the rear wheels to prevent them front turning, safely. Then I started the RX, put it in drive and was able to raise the engine RPM substantially, 2500 RPM I think I remember, with the 1x2 only making creaking sound and the front wheels turning cogizant with the engine speed.

Next I did the same thing in reverse, 1x2's blocking the front wheels. I no more than raised the throttle above idle when both 1x2's snapped.

I published these findings on the internet and got lots of naysayers disputing my testing procedure so I took the RX to nearby Redmond and had the testing done on a four wheel dynamometer. The results were the same, using the rear dyno to brake the rear wheels the engine seemed totally free to drive the front wheels alone. The rear dyno braking had so little effect on engine loading the HP/torque delivered to the rear could not be measured. It ended up taking a matter of tens of seconds before the viscous fluid heated up enough to couple even ~25% of the engine torque to the rear wheels.

As likely most of you know the VC was dropped entirely in 04 in favor of using only brake torque apportioning. The Trac system is used to apply braking to any wheel or wheels that slip/spin beyond the level of the current roadspeed determined by the speedometer or in the case of AWD wherein all 4 might spin simultaneously the accelerometer.

Once the brakes are used in this manner if the condition persists then the engine will be dethrottled (fuel stavation prior to 04, DBW thereafter) to prevent the braking action from overheating the rotors. Since the ABS pumpmotor is relatively smallish, fractional HP, about the same as drive your windshield wipers, it would ordinarily overheat quickly so a 45 second timer limits the period of continuous or semi-continuous use of the RX330 series AWD system.

So if you wish to use wheelspin, rocking back and forth to get unstuck you will need to disable the Trac system first. Simply unplug the MAF/IAT sensor module on the intake downstream of the air filter, let the engine die, plug it back in. You will get a CEL & VSC trouble light but now the Trac will not interfere with intentional wheelspin.

The indications will extinguish after about 4 drive cycles.

I notice that the new RX350 has the VC again but I haven't been able to find out anything about how it might interact, or not, with Trac.

"The Relentless Pursuit of Perfection"

RELENTLESS..............

[stonecutter]

Does/has Lexus ever claimed their AWD is 50:50, or in any other proportionment? If not, then even if it is 95:5, then it's still correct to claim AWD, right? All wheels ARE being driven, just in useless proportions.

Point being AWD is not a hoax, it's $2000 not well spent on this option.

[RX in NC]

We've had a number of true 4x4 Jeep Cherokees and Grand Cherokees since 1985 and there is no question that by comparison, my wife's 2000 RX300 AWD may very well be marketed as "all-wheel-drive" by Lexus, but its 4x4 capability isn't very much at all. As wwest has pointed out a number of times on this forum, the vehicle is very heavily front-wheel biased at all times, and on the rare occasions that it delivers power to the rear wheels, it certainly isn't much.

Our various Jeeps over the years have handled snowstorms approaching two-and-a-half feet deep, and not a single one of them ever got stuck or needed a tow. My favorite one was my 1988 4-liter I-6 Cherokee with a 5-speed manual transmission. The most capable one in the snow was her 1996 5.2-litre V-8 Grand Cherokee that was full-time four-wheel-drive. That one was my wife's favorite vehicle she's ever owned and she felt she could handle any road conditions the weather could throw at her. She put over 160,000 miles on that Jeep but then she caught Lexus fever so, against my advice, we sold her Jeep and she bought her current RX300. Biggest mistake she's ever made car-wise, and if she could have her Jeep back in the condition it was in when we sold it, she would gladly push her RX300 off a cliff and jump back into her Jeep in a heartbeat.

Her RX300 seems to do reasonably well in snowfall accumulation up to approximately 4 to 5 inches. Anything over that and she does not feel comfortable driving the RX300. Again, even though the vehicle is marketed as AWD, what you're driving is pretty much a heavily-biased front-wheel-drive sedan gussied up as a pretend SUV....

[tmastres]

This seems to have gotten a bit comical. My sarcastic nature has to ask, did any of you buy a Lexus RX because you thought it would be a great off road or deep snow performer? If so then I've got a bridge in NY to sell you. Its certainly not marketed as such and I probably wouldnt try driving one in those conditions (seems obvious).

Additionally in my lifetime 4x4 has always implied off-road capabilities while AWD just meant a little better wet and (maybe) light snow or dirt road traction. To compare the two is, well, a bit silly. I've driven my 01 RX in light snow and ice a few times and I was surprised how well it did even as I saw other vehicles having trouble. That could be due to many things though, not least of which is the person behind the wheel. When I lived back east I remember many times seeing people getting hopelessly stuck in 4x4s and others making perfect headway in normal sedans. Go figure

Nonetheless I do have a question for WWEST when you said "So I came home and put the RX up on four jackstands and discovered that there was virtually no drive to the rear wheels." were you referring to your 01 RX or the previous 00 model?

[wwest]

A good indication of the lack of AWD capability of the entire RX (and HL) series is the fact that the factory recommends that tire chains be used ONLY on the front wheels. In point of fact tire chains cannot be used on the rear due to poor tire and suspension element clearances.

Anyone who will willingly drive ANY vehicle with tire chains only on the front in truly adverse conditions for any distance other than a long driveway must have a death wish.

Right in your own owners manual it states that an inordinate level of traction at the front versus the rear can too easily lead to loss of control. Keep in mind that a FWD vehicle with the engine at the front already has more traction at the front vs the rear so it doesn't take adding very much to become unsafe.

This statement is made in regards to having winter tires on the front and not the rear but then with a page or two all that is forgotten so they can tell you to use tire chains ONLY on the FRONT.

I could forgive them that provided a note of caution followed stating that maximum speeds with only front tire chains should be limited to no more than 10 MPH or 5 MPH downhill.

I put 1.5" wheel spacers all around on my 2001 AWD RX300 to provide the clearance necessary for rear tire chains and I carry two sets of chains during the winter months, first on the rear and then the front if needed. And yes, on an RX the rear chains provide more "drag" than drive but that is what is often needed most on really slippery surfaces.

The spacers also allowed me to upgrade to 17X8" wheels and wider summer only Bridgestone Turanza tires. 3" wider stance results in more stability against rollover and the wider tread yeilds more overall traction.

I run summer tires all year around for comfort and quietness and simply throw on the tire chains for the few times they are needed here in the Seattle area.

From time to time I have considered modifying, eliminating, the center differential functionality in favor of a SOLID coupling to the rear and thereby allowing the VC to provide the only front drive torque.

For that reason I was somewhat enthusiastic about the newly available RX350 again having a VC, but I want to wait until I can see and test drive the new Acura RDX first before I make that decision.

By-the-by, it's pretty obvious that Toyota has begun to recognize that FWD and front biased AWD vehicles are inherently unsafe, probably even hazardous for adverse roadbed conditions. For proof just read up on how the new Lexus IS & GS AWD systems dynamically allocate engine torque according to signals from the VSC's yaw sensor.

The documentation on the 4runner isn't as clear, explicit, but the same AWD system firmware seems to have been carried over to it.

The AWD systems in the Volvo XC90, Ford FreeStyle, and now even the Acura RDX are also good examples of how the world is chainging with regards to the poor safety record of FWD.

Rear torque biasing in a Volvo? For an Acura?

Not possible.

[Rx330driver]

This seems to have gotten a bit comical. My sarcastic nature has to ask, did any of you buy a Lexus RX because you thought it would be a great off road or deep snow performer? If so then I've got a bridge in NY to sell you. Its certainly not marketed as such and I probably wouldnt try driving one in those conditions (seems obvious).

Additionally in my lifetime 4x4 has always implied off-road capabilities while AWD just meant a little better wet and (maybe) light snow or dirt road traction. To compare the two is, well, a bit silly. I've driven my 01 RX in light snow and ice a few times and I was surprised how well it did even as I saw other vehicles having trouble. That could be due to many things though, not least of which is the person behind the wheel. When I lived back east I remember many times seeing people getting hopelessly stuck in 4x4s and others making perfect headway in normal sedans. Go figure

Nonetheless I do have a question for WWEST when you said "So I came home and put the RX up on four jackstands and discovered that there was virtually no drive to the rear wheels." were you referring to your 01 RX or the previous 00 model?

Okay, ill admit im not the off roading type, and i live close to no where near snow...but i just feel more confident driving an SUV with AWD...just more confident, and if i perchance drive up to Lake Tahoe or Reno. I guess i dont want to go through the hassle of chains. lol. So yeah, as someone said, it is a $2000 bad decision. I guess thats why the AWD and the FWD differs only a little milage wise

[wwest]

All of the testing I decribed was with the 2001 AWD RX300 and was within the first 6 months of having purchased it.

[Booyah]

So you are saying my 2004 AWD is not awd! ALl I do know is nothing the Alaskan winter through at it even touched it?????

[SW03ES]

We've had a number of true 4x4 Jeep Cherokees and Grand Cherokees since 1985 and there is no question that by comparison, my wife's 2000 RX300 AWD may very well be marketed as "all-wheel-drive" by Lexus, but its 4x4 capability isn't very much at all. As wwest has pointed out a number of times on this forum, the vehicle is very heavily front-wheel biased at all times, and on the rare occasions that it delivers power to the rear wheels, it certainly isn't much.

...

Her RX300 seems to do reasonably well in snowfall accumulation up to approximately 4 to 5 inches. Anything over that and she does not feel comfortable driving the RX300. Again, even though the vehicle is marketed as AWD, what you're driving is pretty much a heavily-biased front-wheel-drive sedan gussied up as a pretend SUV....

Honestly though, you can't compare an RX300 to a Jeep, and the RX isn't designed so any such comparison can be made. The Jeep is rear biased driver selectable 4WD with a low range and lockable hubs, the RX300 is a front biased AWD system with no driver selectable modes and no low range. The Jeep also probably has 3 inches of ground clearance on the RX and rides on light truck tires. The two vehicles are totally different animals and designed to appeal to totally different buyers.

All this nonsense about AWD being a "hoax" is silly, its not a hoax. The vehicle has an AWD system, remember you can buy S500s with AWD now do you think they'd fare as well in the snow as a Jeep? Surely not.

The RX is basically (actually, more than basically) a minivan with 4 doors, anyone that thinks its more than that is fooling themselves.

[bciesq]

The RX is basically (actually, more than basically) a minivan with 4 doors, anyone that thinks its more than that is fooling themselves.

No it's not -- it's a jacked up Camry wagon.

[Napoleon Dynamite voice]GOSH[/Napoleon Dynamite voice]

*Edit to make it clearer that I was kidding.*

[SW03ES]

What I was getting at is that its more similar to a Toyota Sienna minivan than an SUV ;)

[stonecutter]

Not that this dead horse hasn't been beaten enough, the RX350 website's description of AWD...

"The all-wheel-drive system is fully automatic. There is no driver involvement necessary. Vehicle Stability Control (VSC) and Traction Control (TRAC) automatically route power to either the front or the rear wheels as necessary to give a smooth ride and help provide optimum traction [1]."

For TRAC ...

"TRAC senses the onset of wheelspin, then selectively applies the brakes and automatically transfers power to the driving wheel with better grip. TRAC works in conjunction with Vehicle Stability Control (VSC) [1]. VSC senses the onset of a loss of traction in a turn and orchestrates the brakes and throttle to help keep the driver on track."

For VSC ...

"VSC [1] is an electronic system that can aid driver control by detecting incipient sideslip of the wheels while cornering and helping to control it using modulation of engine power and selective application of individual brakes. VSC works in conjunction with ABS and TRAC to help improve driver control under some adverse conditions."

"[1] Lexus Vehicle Stability Control (VSC) is an electronic system designed to help the driver maintain vehicle control under adverse conditions. It is not a substitute for safe driving practices. Factors including speed, road conditions and driver steering input can all affect whether VSC will be effective in preventing a loss of control. Please see your Owner's Manual for further details."

Now, in their FWD RX350 page, they have the exact same description for TRAC and VSC, the only difference is that the AWD description is not there.

So are we to infer from this that in the AWD version, the TRAC and VSC control all 4 wheels where as in the FWD version they control only the front ? If that is the case, then it begs the next question, are TRAC and VSC any less effective in FWD vs AWD?

[wwest]

Not that this dead horse hasn't been beaten enough, the RX350 website's description of AWD...

"The all-wheel-drive system is fully automatic. There is no driver involvement necessary. Vehicle Stability Control (VSC) and Traction Control (TRAC) automatically route power to either the front or the rear wheels as necessary to give a smooth ride and help provide optimum traction [1]."

For TRAC ...

"TRAC senses the onset of wheelspin, then selectively applies the brakes and automatically transfers power to the driving wheel with better grip. TRAC works in conjunction with Vehicle Stability Control (VSC) [1]. VSC senses the onset of a loss of traction in a turn and orchestrates the brakes and throttle to help keep the driver on track."

For VSC ...

"VSC [1] is an electronic system that can aid driver control by detecting incipient sideslip of the wheels while cornering and helping to control it using modulation of engine power and selective application of individual brakes. VSC works in conjunction with ABS and TRAC to help improve driver control under some adverse conditions."

"[1] Lexus Vehicle Stability Control (VSC) is an electronic system designed to help the driver maintain vehicle control under adverse conditions. It is not a substitute for safe driving practices. Factors including speed, road conditions and driver steering input can all affect whether VSC will be effective in preventing a loss of control. Please see your Owner's Manual for further details."

Now, in their FWD RX350 page, they have the exact same description for TRAC and VSC, the only difference is that the AWD description is not there.

So are we to infer from this that in the AWD version, the TRAC and VSC control all 4 wheels where as in the FWD version they control only the front ? If that is the case, then it begs the next question, are TRAC and VSC any less effective in FWD vs AWD?

In actuality both vehicles, FWD and AWD, may have the exact same ECU and firmware. With FWD the rear wheels will NEVER develop wheelspin/slip due to engine torque so that AWD "section" of the Trac firmware will never execute. Otherwise the only real difference being the mechanical aspects, the center differential, PTO, rear driveline, etc, and the VC to hopefully stiffen up if front wheelspin develops.

But then of what use is the VC if Trac is used to simulate a front LSD?

[wwest]

Jeep vs RX comparisons...

NOT!

I think we were comparing the two in relation to our own personal useage, not the extended functionality of the Jeep. I suspect that the clear majority of Jeeps purchased are used in exactly the same way as do RX purchasers.

Basically we purchase because we need AWD functionality as an exception, not as a rule.

The difference is that the Jeep has a long and illustrious history as being world renowned in the area of exceptions, encountering adverse roadbed conditions, simply becuase we all know it also does extremely well in off-road conditions.

But with an RX purchase you don't discover how poorly the AWD implemention is until you inadvertently encounter your first EXCEPTION.

Think about this, if, as in the RX330 series, wheel braking is used to apportion engine torque, how will the new RDX350's VC work if Trac is still used to apportion engine torque? I'm fairly confident that the reason the VC was abandoned in 2004 was because the Trac system even in my 2001 made it useless.

The VC cannot stiffen up and lock, partially, the center differential absent disparate front to rear drive line rotational rates. If, on the RX350, Trac is used throughout, as it is on the previous models, all four wheels, how does disparate rotational rates ever become an issue?

[LEXIRX330]

Well I didn't know I was driving a Minivan!

:chairshot: I have a 1997 Jeep Cherokee 4x4, if I thought for 1 second that I was going to get the same 4x4 system out of a Lexus I guess I would be disappointed. I can not remember Lexus ever comparing the AWD RX to a Jeep or anything else in that class. If my Lexus drove like a Jeep I would have never bought it. If you do not think that the AWD works cut the wheel and make a sharp U turn, and do that with a FWD one and you will see the difference. You will be able to turn sharper with the FWD than the AWD.

I like the way my RX330 handles and I think that the AWD feature is more of a Safety feature. If you want to take your Lexus and play in the mud have fun! :chairshot: I will come pull you out WITH MY JEEP. :D

AWD vs the same with a FWD it looks like it is still worth about 2k more...

Just saw this too. How would this be possible if there is no power to rear wheels?????????

kenpomasta Today, 04:29 PM Post #1

New Club Member

Group: Members

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Joined: Today, 04:05 PM

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Car Model:2003 RX 300 AWD

Location:CT

I just bought a 2003 RX 300 AWD with the lexus CPO program. Ive been very pleased with it for the last 2 weeks that Ive had it, however today it snowed. I was excited to see how it was going to handle expecting it to be better then my old FWD car. To my surprise this RX is not driveable in the snow Any time im trying to turn @ a stop sign Im having major problems. I try to accel a little just like I have drivin every other car. mostly FWDs some with snows some w/o. The rear of the RX is coming out from me. The car keeps getting almost sideways before the vsc turns on and trys to help me. This car has un nerved me. Ive always been a very confident driver in the snow, but this car has me wondering if I should go out or not. Anyone else have problems with this car in the snow.?