Rx400h - Awd (2007)

[rlpiv]

I live on a hill with a steep section of roadway, a steep section of driveway and require a true AWD vehicle. I recently traded my 2002 Rx300-AWD for a 2007 Rx400h-AWD. The day after taking delivery of the Rx400h we got an inch of snow. The Rx400h wouldn’t climb the driveway due to the VSC constricting the power to the drive train(s), but would back up the driveway in reverse (all electric). With this dismal “AWD” performance, I returned the Rx400h to the dealer and agreed (with a financial loss) to accept an Rx350-AWD. In recent snows ranging 5 – 12 inches, the Rx350 is awesome just as the Rx300 was.

In my opinion, the in-ability to switch off the VSC renders the Rx400h-AWD completely IMPOTENT at the very time that the AWD is needed most in slippery conditions.

This vehicle should not be advertised as AWD !!!

Ron Pierson

[Rx330driver]

Well actually, the system on the hybrid isnt a true AWD vehicle. only the rear wheels get electric power, no engine power. THerefore, it doesnt really help. Its not a full time AWD, just two wheels for the most part

[wwest]

I live on a hill with a steep section of roadway, a steep section of driveway and require a true AWD vehicle. I recently traded my 2002 Rx300-AWD for a 2007 Rx400h-AWD. The day after taking delivery of the Rx400h we got an inch of snow. The Rx400h wouldn’t climb the driveway due to the VSC constricting the power to the drive train(s), but would back up the driveway in reverse (all electric). With this dismal “AWD” performance, I returned the Rx400h to the dealer and agreed (with a financial loss) to accept an Rx350-AWD. In recent snows ranging 5 – 12 inches, the Rx350 is awesome just as the Rx300 was.

In my opinion, the in-ability to switch off the VSC renders the Rx400h-AWD completely IMPOTENT at the very time that the AWD is needed most in slippery conditions.

This vehicle should not be advertised as AWD !!!

Ron Pierson

Sorry, but some bad news.

Your RX350 has basically the same VSC/Trac..VDIM system as does the RXh. The only real difference is that since the RXh has no mechanical coupling to the rear drive the RXh has the 2WD/FWD version of TC.

And your problem was actually with TC, Traction Control, the portion of VDIM that prevents wheelspin/slip by moderately braking the slipping wheel(s) in order to sustain a high level of engine torque for apportioning to the wheel(s) with traction. The engine dethrottling is to prevent the brake rotors from overheating due to the need for continual braking otherwise and eventual rotor warpage.

The only advantage the RX350 might have is the VC, Viscous Clutch, used to apportion a higher level of engine torque to the rear with semi-continuous slippage at the front.

I think you may very well have traded one "pig in a poke" for yet another "pig in a poke".

None of these vehicles, RX, HL, Sienna, should be advertised as AWD.

The only front drive "host" based AWD system that I know of that works is the Acura/Honda SH-AWD system. And I would say the RXh actually comes in second to SH-AWD.

As of 2008 the RX350 is getting an off button for TC and VSC. One push turns off TC and a second long depression turns VSC off.

In the meantime you might want to practice feathering the throttle yourself, just lightly on the throttle, just enough for a little front wheelspin/slip to give the VC time to heat up and "lock" the rear wheels into driven mode. That's the way it seems to work best on my 2001 AWD RX300.

[RX400h]

....impressive reply by WWest - good explanation!

[mrc88dal]

Ron,

Did you have snow tires on the 400h when you encountered the traction problem? I live in NH and always mount dedicated snow tires(Blizzaks) on all of my vehicles. With the snow tires on, my 400h routinely plowed through drifts and roadways with 8-12" of snow on them. My area is quite hilly and again no problem climbing very steep grades in snowy conditions. I was concerned when I traded my Sequoia for the 400h but this winter has proven that the RX is a very capable snow performer with the right tires on the vehicle.

[JimsGX]

Ron,

Did you have snow tires on the 400h when you encountered the traction problem? I live in NH and always mount dedicated snow tires(Blizzaks) on all of my vehicles. With the snow tires on, my 400h routinely plowed through drifts and roadways with 8-12" of snow on them. My area is quite hilly and again no problem climbing very steep grades in snowy conditions. I was concerned when I traded my Sequoia for the 400h but this winter has proven that the RX is a very capable snow performer with the right tires on the vehicle.

I have had a similar experience with the 400h this past winter. We had one storm that produced 12-15 inch drifts. I was able to drive through them without a problem with the Michelin OEM tires which were brand new at the time. I'd only had the vehicle for two days when the storm hit. These tires aren't my favorite in the snow (prefer Michelin Cross Terrains) but they worked okay.

Jim

[SOMEONE ELSE'S GOT MY NAME]

Too bad, rlpiv ~ that you chose to 'take your marbles and go home' so to speek. If I may add to wwest's pearls of wisdom; Can you spell, "SNOW TIRES" ? We experienced the same issue with both our Prius, as well as our 400h. The proper tires on ice/snow (and in MT we're allowed to run studs) make all the difference you'd ever need. So you gave up way too quick, without seeking advice at a great place like this forum.

Fact is, if you ARE in a wheel spin situation ... and the car stops ~ regardless whether its because the VSC stops you ... or whether you're stopped due to wheel spin, you're still stopped. There are nut jobs out there who'd just as soon rev their spinning wheels to 5Krpm. That can play havoc to the hybrid system. If you DO need better results ... and trust your self to not over rev when wheels break free, and can't afford the proper tires you OUGHT to be using in ICE/SNOW, there IS a way to over-ride the VSC / ICE cutting out. It's as simple as unplugging the modular sensor connectors (but I didn't tell you that :whistles: ). I got that gem from a Toyota tech who shall remain nameless. It works, in that flash storm situation, prior to having a chance to get the studded set mounted.

[SW03ES]

Did your 400h and your 350 have the same tires? I bet you the problem was tires.

Anywho one drawback to a hybrid in the snow is that the traction control is designed not to allow ANY wheelspin because the effects of it would be detrimental to the hybrid system. Makes operating them in that specific situation difficult.

I do agree with wwest though, if you need a "true" AWD vehicle no RX is it. You need something like a GX.

[rlpiv]

Did your 400h and your 350 have the same tires? I bet you the problem was tires.

Anywho one drawback to a hybrid in the snow is that the traction control is designed not to allow ANY wheelspin because the effects of it would be detrimental to the hybrid system. Makes operating them in that specific situation difficult.

I do agree with wwest though, if you need a "true" AWD vehicle no RX is it. You need something like a GX.

===================================================================

Gosh …. There are a few comments above that I must respond to.

Foremost, I DID NOT HAVE A TRACTION PROBLEM so TIRES ARE NOT AN ISSUE !!

1. My problem with the '07 RX400h-AWD was not traction (static or dynamic friction) of the new factory tires to the snow surface. Remember that I could back up the driveway (all electric) but it just wouldn't go up frontward (multiple demonstrations each) in an inch of snow that became packed. My problem was that a combination of VSC, TRAC & VDIM was totally constricting the engine power to the front wheels (engine and MG2) and electric power to the MGR. It would not apply enough power to break the static friction of the tires to the snowy surface at a very low speed.

2. As stated in my initial writing, my new '07 RX350-AWD is awesome, as was my '02 RX300-AWD. These vehicles meet my entire expectation of AWD and will accept increasing ("feathered") engine power to all drive wheels until ALL FOUR tires break static friction on a snowy / icy surface. I couldn't ask for a better AWD performance … and if I needed more TRACTION, I know that I could (and would) move to a Snow Tire.

3. NET: The RX350 will climb my snowy driveway without any wheel spin but the RX400h just stopped due to an uncontrollable restriction of engine and electric to the drive wheels. I was, and am, really very disappointed that the RX400h-AWD cannot yet meet an AWD performance expectation easily demonstrated by the other RX models.

Ron Pierson

[wwest]

Did your 400h and your 350 have the same tires? I bet you the problem was tires.

Anywho one drawback to a hybrid in the snow is that the traction control is designed not to allow ANY wheelspin because the effects of it would be detrimental to the hybrid system. Makes operating them in that specific situation difficult.

I do agree with wwest though, if you need a "true" AWD vehicle no RX is it. You need something like a GX.

===================================================================

Gosh …. There are a few comments above that I must respond to.

Foremost, I DID NOT HAVE A TRACTION PROBLEM so TIRES ARE NOT AN ISSUE !!

1. My problem with the '07 RX400h-AWD was not traction (static or dynamic friction) of the new factory tires to the snow surface. Remember that I could back up the driveway (all electric) but it just wouldn't go up frontward (multiple demonstrations each) in an inch of snow that became packed. My problem was that a combination of VSC, TRAC & VDIM was totally constricting the engine power to the front wheels (engine and MG2) and electric power to the MGR. It would not apply enough power to break the static friction of the tires to the snowy surface at a very low speed.

2. As stated in my initial writing, my new '07 RX350-AWD is awesome, as was my '02 RX300-AWD. These vehicles meet my entire expectation of AWD and will accept increasing ("feathered") engine power to all drive wheels until ALL FOUR tires break static friction on a snowy / icy surface. I couldn't ask for a better AWD performance … and if I needed more TRACTION, I know that I could (and would) move to a Snow Tire.

3. NET: The RX350 will climb my snowy driveway without any wheel spin but the RX400h just stopped due to an uncontrollable restriction of engine and electric to the drive wheels. I was, and am, really very disappointed that the RX400h-AWD cannot yet meet an AWD performance expectation easily demonstrated by the other RX models.

Ron Pierson

"..It would not apply enough power to break the static friction of the tires to the snowy surface at a very low speed.."

If that statement is true then some real majic was going on.

Since TC has no method of determining that the surface is slippery "beforehand" then TC will NOT apply "traction" braking unless wheelslip/spin has already been detected using the 4 ABS wheelspeed sensors as "cross" references. Since power is applied only to the front on initial gas pedal depression it will almost always be the front wheel(s) that develop wheelspin/slip should the surface be slippery enough. Another shortcoming of this technique is not so obvious. Even if only one of the front wheels slips then BOTH will be braked by the traction control system. To do otherwise might result in the stearing wheel being yanked from the driver's hands (can you say "broken thumbs??) with the resulting extreme torque stear.

I notice the new RAV4 has an "auto LSD" function (enables differential traction braking at the front) that can be activated in these instances but with the appropreate "broken thumbs" caution note in the owners manual.

And yes, because there is no mechanical coupling to the rear for use of braking to maintain a high torque level AND apportion it to the rear engine dethrottling will be absolutely simultaneous with traction braking, just as with the FWD only version of the RX or RXh.

So, why did your RX400h develop enough wheelspin/slip so as to dethrottle the engine(s)...??

Not enough "static" traction between the tire tread and the packed snow or icy surface...!!!!!

Had the aforementioned event happened to me my first reaction would have been to get out and put the rear tire chains on. Were I to own an RX400h I guess that would mean installing all four tire chains as I consider tire chains only on the front to be a patently UNSAFE practice.

Is it possible that the RX400h has such an abundance of TORQUE (in SPADES!) at initial startup that it becomes impossible to feather the throttle to a low enough level so as to not develop wheelspin at initial startup on a slightly slippery surface?

Might that abundance of TORQUE have been the real problem you encountered?

Does the RXh not have a SNOW mode..?

-----------

Later thoughts...

I wonder...

Does the RXh have so much low end startup torque that TC must be very, SUPER, quick acting? Traction braking and engine dethrottling the very instant even the slightest level of wheelspin/slip occurs?

I know that my 2001's VSC has activated even though my "seat of the pants" sensor never even detected an "out of whack" circumstance. It was only in retrospect, looking back at the circumstances, fast/tight turn and a water puddle, that I came to realize why VSC had activated. Is that what happened here, your RXh had such a quick and brief, brief due to TC, instance(s) of wheelspin/slip that you thought there was no cause for TC's activation?

[LexRexBlue]

There are times when this forum is too technical for me! In short, are you saying that if there is a lot of snow I should drive my '99 RX 300 with Cross Terrain tires (awd) instead of the newer RX 400h awd with dismal Goodyears??? To be honest I always felt like I had better control with the old RX but just assumed it was the tires. I live on a hill but have never had any problems with the 400h. In fact when we were too lazy to clear the mound of snow/ice at the bottom of the driveway (about 12+ inches) I just drove over it.

[wwest]

There are times when this forum is too technical for me! In short, are you saying that if there is a lot of snow I should drive my '99 RX 300 with Cross Terrain tires (awd) instead of the newer RX 400h awd with dismal Goodyears??? To be honest I always felt like I had better control with the old RX but just assumed it was the tires. I live on a hill but have never had any problems with the 400h. In fact when we were too lazy to clear the mound of snow/ice at the bottom of the driveway (about 12+ inches) I just drove over it.

Your 99 doesn't have TC nor VSC, but probably does have a rear mechanical LSD. So yes, YOU were probably more "in control" of the 99 than of the RXh with VDIM, etc.

Maybe the '08 RXh will also have the ability to disable TC and VSC, although I really don't see a need for disabling VSC.

[mrc88dal]

I still feel that dedicated snow tires would've solved this problem at less cost than trading in a new 400h. If you look at the location of the RX's in the above posts you can see that those of us who live in hilly/snowy areas have no problems whatsoever with the 400h's snow performance. I don't believe our cars came equipped with a different AWD system but did have the benefit of snow tires and different drivers.

[wwest]

I still feel that dedicated snow tires would've solved this problem at less cost than trading in a new 400h. If you look at the location of the RX's in the above posts you can see that those of us who live in hilly/snowy areas have no problems whatsoever with the 400h's snow performance. I don't believe our cars came equipped with a different AWD system but did have the benefit of snow tires and different drivers.

"...I don't believe our cars came...."

Don't be too sure about that, "non-tangiable" running changes to software/firmware, say TC, can be non-obvious except in certain circumstances. Given the industry's seeming current attention to the hidden hazards of FWD vehicles I wouldn't be surprised if running changes have been made to TC in order to reduce those hazards somewhat.

[SOMEONE ELSE'S GOT MY NAME]

I still feel that dedicated snow tires would've solved this problem at less cost than trading in a new 400h. If you look at the location of the RX's in the above posts you can see that those of us who live in hilly/snowy areas have no problems whatsoever with the 400h's snow performance. I don't believe our cars came equipped with a different AWD system but did have the benefit of snow tires and different drivers.

You won't be able to convince rlpiv that's true because he didn't have to drive backwards in his non-hybrid ... and in his/her mind that means it must be the car. Prius owners make the same "no it isn't yes it is" a problem comments. For those who haven't tried mongo snow tires, they'll never know. We drive Mt snow / ice / hilly terrain and the snow / stud tires make all the difference.

[wwest]

I still feel that dedicated snow tires would've solved this problem at less cost than trading in a new 400h. If you look at the location of the RX's in the above posts you can see that those of us who live in hilly/snowy areas have no problems whatsoever with the 400h's snow performance. I don't believe our cars came equipped with a different AWD system but did have the benefit of snow tires and different drivers.

You won't be able to convince rlpiv that's true because he didn't have to drive backwards in his non-hybrid ... and in his/her mind that means it must be the car. Prius owners make the same "no it isn't yes it is" a problem comments. For those who haven't tried mongo snow tires, they'll never know. We drive Mt snow / ice / hilly terrain and the snow / stud tires make all the difference.

"...You won't be able to convince..."

I dunno, not too sure.

Driving backwards very significantly reduces the level of HP/Torque available and would have made it much easier, a whole LOT easier IMMHO, to "feather" the throttle to simulate a snow mode type driveline.