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Toyota Avalon 2008-2010

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Comments

  • nceencee Posts: 419
    Well they ordered a axle today, and when it comes in, and they then take it apart, they will see if thats the problem.

    They said everything pointed to the axle, but if they take apart I would be without the car for a few days? They didn't have a car they could let me use for a few days???

    Now if that isn't the problem when the part comes in, the will have to provide me with a loaner, as my car will be torn down.

    They said the part should be here next Tuesday, and unless something happens before then, I have an appointment to drop if off next Friday afternoon.

    I'll let folks know the out come.

    So based on the above comments, this may be a temporary fix? Replacing the part, but not fixing the issue surely isn't the way to FIX the problem … or is it?

    Skip
  • Skip,

    It is very possible the noise you hear coming from the front left corner of your vehicle is that of the brake actuator motors for the ABS, traction control and VSC systems, which are controlled by solenoid valves. The valve themselves are a little bit noisy, with the motors being the noisiest. This operation is required in order to monitor the integrity (safe/fail) of the above systems. I do hear a subtle grinding noise coming from the front left side of my car, but I’m confident there’s nothing wrong with it.

    Now about your transmission:
    The anchor-dragging effect you feel when you release the gas pedal is normal. Upon releasing the gas pedal your automatic transmission downshifts in order to slow down the car. The Avalon transmission has high gear ratios on the low gears, specially the first gear (3.30:1). In other words this means, the higher the gear ratio the stronger the “engine-braking” force will be. It is that force you feel that is effectively slowing down your car dramatically, which is primarily due to the high gear ratios on the reduction gears. If you are very familiar with all these concepts I can give you more in-depth details of how the Avalon’s tranny works. I also have the same experience with my transmission, but I’m confident there’s nothing wrong with it.

    Another point you should know is, when the engine coolant and transmission fluid temperature is cold your tranny will cycle between first, second and third gear only; the colder the temperature the longer the tranny will remain in this state. This restriction makes the tranny behaves a bit "abnormal"; however, when the vehicle reaches operating temperature (gauge temperature needle in you dash is half-way) your tranny will cycle through any gear depending on your speed only.

    Amaury
    '08 Limited
  • wwestwwest Posts: 10,706
    "...The anchor-dragging effect...when you release the gas pedal is normal...."

    NOT, NO, NEVER...!!!

    There are NO automatic transmissions and absolutely NO FWD or F/awd modern day vehicle that will automatically downshift when the driver releases the gas pedal. For FWD or F/awd that would be 'way too dangerous. Almost all transaxles will actually upshift in this circumstance.

    On the other hand if you should apply the brakes even ever so lighty you might encounter this "anchor-dragging" effect.

    On the "third" hand, if the gas pedal is released QUICKLY while the transaxle is still in a low gear (1st..??) the ECU will assume the intent is to slow the vehicle using engine compression braking and remain in the lower gear.

    But an actual downshift, not..!!

    Unless you then apply the brakes, maybe.
  • Now that you have taken an "all knowing" position on the deceleration issue, I suggest that you drive an Avalon (and maybe other Toyota vehicles) and experience first hand the transmission downshift that helps deceleration on downhills, etc., prior to any actual braking.

    My 07 Avalon was the first vehicle I have owned that utilized this feature, and it seems to work rather well. The braking effect is more noticeable at lower speeds.
  • nceencee Posts: 419
    Thank you for the insight. I believe, and so does the dealer, that the 'Grinding noise" is a bit LOUD and not normal. It's loud enough that folks standing around will say something or point to my car as I drive by. It only started to happen recently, and I'm comfortable it's not normal. I never had it on my 2007 Camry or my wife''s 2003 Camry, or any other toyota / car we've owned. If it is normal, I would give some consideration to trading the car, as it sounds like the front end is going to fall off, or at best seize up or something.

    As for the anchor dragging effect … I don't like it. I better understand it now, but I don't like it. I would think the car would get much better MPG if it didn't do this, and I never heard anyone say, they wish their car did it, and if it had, they would not have had that accident. But I know living in an area with tons of hills / mountains, I would much prefer if it disengaged when I let up, so that I could go to the road and take advantage of coasting.

    Skip
  • finfin atlantaPosts: 591
    As to the automatic transmission, post #515 is 99.9% correct. Under normal conditions, when the accelerator is released, automatic transmissons will go to a higher gear or remain in the same gear, depending on speed. To downshift to a lower gear would be at least unpleasant and possibly dangerous in some cases, such as low traction situations. Also, as #515 points out, low vehicle speed and/or brake application may alter the normal shift pattern and produce different results.

    That said, my '07 Limited does, on occasion, at certain speeds, while slowing under certain conditions, actually go to 4th gear from 5th for no reason. On rare occasion it has even gone from 4th to 3rd for no apparent reason. If anyone else observes this illogical behavior, you are not alone. :confuse:

    And, never allow an AT car to disengage or "coast" in neutral. There are multiple risks in this, not the least of which is lack of vehicle control. There is no direct clutch as in a manual shift to connect the engine to the road and help control the car. Allow the top gear to work and drive "connected".

    Enjoy the Avalon..... great car.. !
  • wwestwwest Posts: 10,706
    '...And, never allow an AT car to disengage or "coast" in neutral.."

    IMMHO this is yet another "urban legend", or more correctly stated, an "old wives tale".

    Many, many years ago the gearbox, non-synchro gearbox, was considered to be a key part of the braking system. Back in those days finding yourself "out of gear" and gaining speed downhill could be a heart in throat event, if not worse.

    Many states still have these laws on the books obsolete as they may be.
  • It is now obvious to me that the dragging effect on the Avalon has nothing to do with downshifting. Funny, but I have the indication in front of me all this time (in the dash) but I overlooked it. Thank you wwest for making me dig deeper.

    However, wwest, if I’m traveling at 30 mph, and contrary to your suggestion, the Avalon transaxle will NOT upshift upon releasing the gas pedal; low speed restriction won’t allow engagement past the 3rd gear. Since it can’t go up or down the obvious conclusion is that it remains where it is in terms of gear.

    The abrupt deceleration the Avalon experiences when the gas pedal is released could be the result of the mechanical decoupling between torque converter and transmission. Engagement between the two still continues by means of fluid coupling. The ability of the Avalon to disengage the lock-up clutch upon releasing the gas pedal is a feature not found in every modern car; my daughter’s ’03 Camry I4 does not have it and certainly my previous Camry ’04 V6 didn’t have it either.

    No matter what, there’s no question in my mind that the dragging effect is part of the normal operation of the Avalon, and as far as I’m concerned its mile-per-gallon is very close to that of my daughter’s Camry (in both city and highway) and much better than my old Camry ’04 V6.

    Amaury
    ’08 Limited
  • wwestwwest Posts: 10,706
    I've most likely overstated.

    Its not that these transaxles will not downshift during a "full throttle lift" coastdown, just that they will not downshift to a ratio wherein a significant level of engine compression braking will be felt/incurred.

    In reality in this situation an upshift is much more likely and it is those inadvertent upshifts that Toyota and Lexus are having the most trouble with(***). Not the upshift itself, mind you, but the need, often randomly ocurring need, for a quick return to acceleration. An acceleration that requires a downshift but now with the engine already at idle (little/no ATF pumping capacity) and that previous "inadvertent" upshift just having EXHAUSTED all of the ATF line pressure.

    And be aware that while the transaxle will not "downshift" during a full lift throttle coastdown, even the slightest touch of theh gas pedal will often result in a downshift into the most appropriate gear range for your current road speed.

    Now...the lock up clutch.

    Almost all, if not all, automatic transaxles will release the lock up clutch the INSTANT you apply any level of braking as otherwise the "solid" engine/gearbox coupling might result in stalling the engine.

    And.. you are right but for the wrong reasons.

    The "feeling" you have is much more likely due to the lock-up clutch being engaged, resulting in a "solid" coupling rather than the "soft" one with the torque converter in the drive path.

    If you have carpet mats be sure they are well secured and cannot slide forward over time. There are instances of un-intended acceleration due to the mat sliding forward and getting trapped behind the brake pedal but lying over the top of the gas pedal. Apply the brakes severely and the mat forces the gas pedal down.

    In your situation that might even be the reason your car is downshifting inadvertently. Move your foot to the "wrong" place on that carpet mat and the gas pedal gets "nudged" slightly down and the transaxle downshifts accordingly.

    *** I first noticed this anomally in my 2000 AWD RX300. As I slowed or braked ligthly to come to a stop at about/below 10MPH the RX would feel as if someone had bumped me slightly from behind. And in slowing, braking lightly or not, coastdown, from 40-30 MPH the RX would get a slingshot feeling, a feeling of "surging" forward as if I had let up on the brakes.

    This was all the result of a transaxle design modification Toyota made late in the last century which resulted in a flaw for which they have yet to come up with a satisfactory fix.

    With the engine at idle the ATF line pressure cannot be sustained to/at a level to keep the clutches tightly enough engaged to support even the slightest level of
    torque for engine compression braking so that issue is eliminated by simply upshift the transaxle.
  • "Almost all, if not all, automatic transaxles will release the lock up clutch the INSTANT you apply any level of braking as otherwise the "solid" engine/gearbox coupling might result in stalling the engine.

    And.. you are right but for the wrong reasons."


    Don’t go so fast my friend.

    I’m talking about a specific design, that of the U660E transaxle found in my car You are, however, talking in general, which it may or may not apply to that transaxle.

    Here’s a fact about the 3rd generation Avalon transmission that you are not aware of:

    1. The torque converter clutch lock-up mechanism is engaged in all gears regardless of vehicle speed as long as:
    Engine coolant temperature is equal to or greater than 140° F (otherwise, it won’t engage)
    You don’t step on the brake pedal (otherwise, it will disengage)
    You don’t release the gas pedal. (otherwise, it will disengage)

    Here’s another fact you are not aware of about the U241E transaxle found in my daughter’s 2003 Camry I4 and the U140E found in my old 2004 Camry V6.

    2. The lockup torque converter mechanism is not engaged in all gears. Requisites for engagement:
    Engine coolant temperature is equal to or greater than 122° F (I4) and 131° (V6)
    You don’t step on the brake (there’s no mention about gas pedal)

    Whoever has owned the Camrys above know for fact these cars’ tremendous ability for coasting. Can I relate this with the metal-to-metal coupling between torque converter and transmission? I have plenty of privileged information to find the answer. I just need the time.

    Facts 1 & 2 are neither my imagination nor my invention. Rather, they’re Toyota’s.

    Amaury
    ’08 Limited
    ps: thx for the carpet mat thing. It was a very good piece of advice.
  • wwestwwest Posts: 10,706
    Actually I went to techinfo.toyota.com and researched the issue before replying.

    Your statements verify mine...

    The lockup clutch will remain engaged provided:

    "..you don't step on the brake pedal.."

    And I'm quite sure the lockup clutch remains disabled in the lower gear ratios wherein the converter's torque multiplication aspect is more often required than not. There is also the case that were it actually locked up, say in 1st or 2nd gear, you might stall the engine with a quick release of the gas pedal.
  • When I said I have privileged information I wasn’t talking about 8 ½ “ x 11” hardcopies but 22” x 34” (ANSI D) printouts as well.
    The tranny is delicately complex: way too many hydraulic circuits, sensors and actuators. But I’ll see if I can find a common denominator here regarding the dragging issue

    This stuff certainly defies just about anyone’s common sense.

    Amaury
    ’08 Limited
  • wwestwwest Posts: 10,706
    "..find a common denominator..."

    These days that would be the source code for the engine/transaxle controlling ECU/microprocess(s). And I don't think either of us will have access to that.

    The best, and maybe the only, close alternative will be the manufacturer's disclosed information about the dynamic operation, shift pattern, etc.

    The new RX/Venza F/awd system's electrical schematic, as a "for instance" includes the OAT (Outside Air Temperature) as an input. That could/might mean the outside temperature is being taken into consideration to determine when to engage, or how hard to engage, the rear drive clutch. Or it could mean the new F/awd system is subject to overheating(***) and the system operates accordingly.

    *** The Ford Escape was an early adopter of this "new" F/awd system and actually had an instrument panel warning to indicate that the F/awd system was overheating (rear clutch pack was implied) requiring the driver to pull over long enough for the system to cool. The Mazda CX-7 uses this same system and has added water cooling for the PTO (Power Take Off) to prevent it from overheating.

    My point is that it often requires many resources, sometimes somewhat obtuse resources, in order to try to figure out how these microprocessor controlled systems operate.
  • I just got gas for my '08 Avalon; it had 16 miles to go and the low fuel indicator was on. I was only able to squeeze in 16.005 gallons and I really tried hard. Why is it with all the electronic gadgets and things there can't be an accurate gas gauge?
  • wwestwwest Posts: 10,706
    Probably liquid heat/cool expansion/contraction more than anything else.
  • wwest,

    "And I don't think either of us will have access to that".
    Sitting on my desk are blueprints of stuff that ranges in the million of dollars (electromechanical, hydraulics, logic controller diagrams; you name it); would you like to take a peak? Cars’ blueprints are proprietary information only NOT top secret information. Not available in Google of course, but obtainable nevertheless. In this arena, I have the advantage mi amigo.

    "And I'm quite sure the lockup clutch remains disabled in the lower gear ratios wherein the converter's torque multiplication aspect is more often required than not. There is also the case that were it actually locked up, say in 1st or 2nd gear, you might stall the engine with a quick release of the gas pedal." Looking at this stuff, it’s clear to me that the automatic transmission has its own set of clutches; so even if it is engaged to the torque converter clutch (lockup), provisions can be set in place to engage/disengaged whatever set of planetary/sun gears depending on unique trait designs. The fact is, with such design characteristics logics can be implemented to have the transaxle downshifts even when YOU let go of the gas pedal in whatever gear wheather you're on flat or going downhill (have you ever heard about automatic engine braking when going on a downward slope as the tach needle shoots sky high?). This is all against your perception of how tranny works.

    Amaury
    ’08 Limited
  • wwestwwest Posts: 10,706
    Sorry, I've just never seen or heard of computer source code in "blueprint" form, nor being referred to in that manner.

    "..The fact is..."

    Yes the whole idea of computer firmware control of the electric solenoids which in turn control the various clutches via porting hydraulic pressure is to have total control and viability of the transaxle.

    But just as you would NEVER declutch a stick shift in a low enough gear ratio that would result in a high level of engine compression braking absent being sure, certain sure, of the roadbed traction coefficient these transaxle should never also.

    No blueprints, source code, just common everyday horse sense.
  • wwestwwest Posts: 10,706
    "..(have you ever heard about automatic engine braking when going on a downward slope as the tach needle shoots sky high?)..."

    No, and I'm quite sure you haven't either. Modern computer controlled transaxles (assume FWD) will only downshift in the above circumstance provided there are first "armed" via the driver applying some level of actual braking, even light braking. "sky high" is a pretty subjective term and so it is not one I would use in describing the level of engine RPM rise that would be likely to occur with an "automatic"(no shifter or paddle movement) FWD downshift. "Automatic" FWD downshifts, even RWD downshifts, dare not be that dramatic in the described circumstance, automatic downhill engine braking.

    A driver induced, shifter movement, downshift, maybe, but NEVER an automatic one.
  • Sorry. The term blueprint is commonly used among those shuffling designs printed in any large form of paper (usually larger than 11” x 17”); not necessarily the typical white lines in blue background. But all this information is in CAD; not AutoCAD but Bentley’s Microstation along with I-DEAS (if you know what that is). That’s the only reason I extended you the invitation to take a peek; since these drawings along with schedules are already digitized. I can even change the design at will to show you I have full rights to edit these files.

    …design files from companies you know; all rightfully obtained.

    And the invitation remains open.

    Amaury
    ’08 Limited
  • wwestwwest Posts: 10,706
    I pass...

    73's
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