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cduluk

Rx400H Cvt Transmission

18 posts in this topic

Hey guys!

Does anyone know anything about the CVT transmission that are used in the Rx400h? As a previous Rx300 owner (which is well known for transmission issues) I can't help but worry about the CVT.

I researched "CVT transmissions" on google and found some "general" information as to how CVT's work, but I couldn't find anything specific to the Rx400h.

I'm just wondering how reliable this transmission is compared to the standard automatic. It seems to me that this is very new technology which makes me worry a bit.

I haven't found any reports concerning Rx400h transmission failures, but considering the Rx400h is only 4 years old, it doesn't mean much...

I notice while driving the Rx400h, the engine seems to rev MUCH higher and for long period of times even though the car doesn't move much (especially during acceleration). This implies that parts in the transmission are also moving very rapidly for long stretches of time. It just "sounds" like the transmission and engine are working a LOT harder than the standard Rx350 transmission and engine would be.

But on another note, the Rx400h transmission "feels" a lot smoother than the standard transmission. The CVT eliminates that "lag" between gears that one typically feels in a normal automatic transmission. Acceleration in the Rx400h is completely linear with no lags or what not. And this makes me think that the transmission is under very little stress when accelerating.

So what do you guys think? Should I worry about the reliability of the Rx400h transmission?

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Don't worry - be happy.

You'll learn soon enough (incl. on this forum)if there are problems!

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59K and mine is going strong, however i did buy the extended warranty. I do like that there is synthetic trans fluid in there, not crazy about no dipstick to check the fluid color, odor and quantity. i really do hope the tech who services my lexus really does poke his finger in the trans fluid reservoir every 30K as scheduled.

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59K and mine is going strong, however i did buy the extended warranty. I do like that there is synthetic trans fluid in there, not crazy about no dipstick to check the fluid color, odor and quantity. i really do hope the tech who services my lexus really does poke his finger in the trans fluid reservoir every 30K as scheduled.

I will say this about how bullet proof the HSD is. Out of over TWO MILLION hybrids running around the landscape with HSD, I've only heard of a couple persons having problems ... & I've looked for them on the web, different forums etc. In addition, although the Stealership will want you to come in sooner, the CVT does NOT need to have its fluid changed for NINTY thousand miles. This nuget was given to by by TWO hybrid tech specialists ... but if you want to wast perfectly good fluid, knock yerself out!

:lol:

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By the very nature of a CVT its going to be more reliable than a standard transmission, fewer moving parts...no gears...etc.

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Oh nice! That's really good to hear. <_<

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By the very nature of a CVT its going to be more reliable than a standard transmission, fewer moving parts...no gears...etc.

I am confused over the "no gears" comment. It is my understanding that the CVT is a planetary gear arrangement consisting of a sun gear, ring gear, planet gears and planetary gear carrier---all are gears.

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59K and mine is going strong, however i did buy the extended warranty. I do like that there is synthetic trans fluid in there, not crazy about no dipstick to check the fluid color, odor and quantity. i really do hope the tech who services my lexus really does poke his finger in the trans fluid reservoir every 30K as scheduled.

I will say this about how bullet proof the HSD is. Out of over TWO MILLION hybrids running around the landscape with HSD, I've only heard of a couple persons having problems ... & I've looked for them on the web, different forums etc. In addition, although the Stealership will want you to come in sooner, the CVT does NOT need to have its fluid changed for NINTY thousand miles. This nuget was given to by by TWO hybrid tech specialists ... but if you want to wast perfectly good fluid, knock yerself out!

:lol:

ATF-WS is cheap(ish) and changing the fluid is quite easy. I changed the fluid in the MGR (rear diff) and the tranny at 115000 kilometres. While colour is not a great indicator of fluid condition, the fluid I put in looked much nicer than the fluid that came out.

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By the very nature of a CVT its going to be more reliable than a standard transmission, fewer moving parts...no gears...etc.

I am confused over the "no gears" comment. It is my understanding that the CVT is a planetary gear arrangement consisting of a sun gear, ring gear, planet gears and planetary gear carrier---all are gears.

Those gears are more a part of the HSD power balancing between the gas engine and the electric motors inputs than they are part of the CTV.

The CTV operates by simply walking a metal band in and out over a conical shaped drive to change the ratio between input (from those gears) and out to the wheels.

perhaps a visit to howstuffworks would be instructive.

http://auto.howstuffworks.com/cvt2.htm

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By the very nature of a CVT its going to be more reliable than a standard transmission, fewer moving parts...no gears...etc.

I am confused over the "no gears" comment. It is my understanding that the CVT is a planetary gear arrangement consisting of a sun gear, ring gear, planet gears and planetary gear carrier---all are gears.

Those gears are more a part of the HSD power balancing between the gas engine and the electric motors inputs than they are part of the CTV.

The CTV operates by simply walking a metal band in and out over a conical shaped drive to change the ratio between input (from those gears) and out to the wheels.

perhaps a visit to howstuffworks would be instructive.

http://auto.howstuffworks.com/cvt2.htm

Lexus does not use the conical pulley and belts. The planetary gears in the power split transmission together with the computer, power electronics, battery pack and motor-generators provide the variable speed. Here is a beautiful picture of the 600h drive. http://en.wikipedia.org/wiki/File:CVT_for_Lexus_600h.jpg Isn't this a beautifully engineered product?

Here is an excellent description of how it works. Explains how the engine is started without a starter motor, how the car reverses without a reverse gear, and the mechanics of how power is split between the engine and the motors. May have to read it a few times to fully understand. http://en.wikipedia.org/wiki/Hybrid_Synergy_Drive

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I have a 2008 RX400h. Is there a speed maximum speed in which I should not downshift with the CVT transmission? Maybe I don't know how CVTs work but I could not find anything in the manual.

I do notice when downshifting that my regeneration meter goes up so maybe it's not really downshifting but instead applying the regenerative system?

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You can't downshift because there are no gears...

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on the 2010 450h i noticed lexus put some preset first second and third gear positions to 'simulate' the ability to shift the cvt, lol was that on the 08 also?

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You can't downshift because there are no gears...

I used the incorrect term, by downshift I meant engine braking. Is there a max speed at which I should not shift to the "B" gear when wanting to engine brake?

From the manual online:

The transmission will feel different.

The RX400h uses an Electronically-controlled Continuously Variable Transmission (ECVT). The transmission does not shift with fixed gear ratios like a conventional transmission, so it delivers power efficiently and smoothly. The “B” gear position is for engine braking.

http://www.lexus.com/pdf/models/rxh_driving_performance_guide.pdf

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on the 2010 450h i noticed lexus put some preset first second and third gear positions to 'simulate' the ability to shift the cvt, lol was that on the 08 also?

The '08 does not have this. IMO, I would prefer to have those various simulated gears for engine braking down canyons and such.

I found this CVT tech brief interesting. Apparently Audi's latest CVT is faster and more fuel efficient than the manual and automatic:

http://www.sae.org/automag/techbriefs_01-00/03.htm

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There's no speed at which you shouldn't use B...

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I use the "B" mode quite often, it's a great feature. It's an easy way to slow the car down without having to hit the brake. Sometimes in moving traffic when the car in front of me slows down, I just whip it into "B" and the car lags a bit, and when my speed is OK I just put it back into "D".

It's also nice to use when getting off the highway when you need to slow down "just a little bit".

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I use the "B" mode quite often, it's a great feature. It's an easy way to slow the car down without having to hit the brake. Sometimes in moving traffic when the car in front of me slows down, I just whip it into "B" and the car lags a bit, and when my speed is OK I just put it back into "D".

It's also nice to use when getting off the highway when you need to slow down "just a little bit".

I am starting to use "B" in a similar manner. The question of using it at any speed came up when there was one time I engine braked down a long canyon but had forgotten that I was still in "B". I ended up speeding to freeway speeds and drove a couple miles before realizing I was still in "B". I'm glad to hear that I can use "B" at any speed because I wasn't sure if I might have put extra stress on the engine from that mistake.

Have you noticed when you shift to "B" that your regenerative braking needle increases (creates more electricity), does that mean it applies generators to create drag versus versus using the CVT in a different gear ratio?

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