Transmission Activity

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We're greatly enjoying our 2007 Odyssey EX. One thing I'm confused about, however, is the transmission 'activity'.... By that I mean that it seems to downshift when you take your foot off the gas and are
slowing down. This is confirmed by watching the tachometer tick upwards as you feel the transmission downshifting. Since our last van was a '99 Windstar (I was happy when it would simply UPshift!) and my other car is a 6-speed Audi A4, I guess I'm not used to the electronics in the latest transmissions. Is this really the case - that the car downshifts? Or is my transmission about to fall out!
Thanks.
Dan D Central NJ USA '07 Odyssey EX
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Dano58, wrote the following at or about 1/2/2007 2:29 PM:

I noticed the same thing with my 2006 Accord EX. Read the owner's manual, at least I think that's where I read it, and there was an explanation that made sense to me. It DID take some getting used to though. No doubt about it.
IIRC, the computer senses a number of things including braking, incline, etc and decides whether to just let you coast or to downshift to provide extra braking. Now, with 8,000 miles under my belt on the car, I rarely notice it.
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On Tue, 02 Jan 2007 12:29:39 -0800, Dano58 wrote:

Yep, they downshift.
It is used to help your brakes last longer, and to help aggressive braking stop faster.
This is a good thing.
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It called "Logic Grade" , that is why you won't grind up your rotors..read up on it.

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On Wed, 03 Jan 2007 03:07:21 GMT, "Andy & Carol"

I would think that it would hurt your gas mileage though. At least it would if you are anticipating a stop and just want to coast until the light changes. Is it possible that it waits for you to touch the brake pedal before it downshifts? That would make more sense.
On the upside, completing the downshift earlier makes it ready to accelerate on short notice. All-in-all, that is one reason why I prefer manual transmissions. The AT will never have enough sensors until they put in one that can read my mind.

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Gordon McGrew wrote:

which is precisely what it does do - it takes the signal from the brake pedal switch.

you haven't driven an automatic lately.

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On Tue, 02 Jan 2007 22:06:04 -0800, jim beam

My understanding is that the cars do learn how you drive. Now, I'm not really a car guy, but I'm a computer programmer. I can certainly see how the computers could learn how you drive and act on it, but it would also need to understand that a car can have more than one driver. Until you actually have to log-in, it might get confused. Now is this the guy with the lead foot or the lady with the sweet disposition?
Perhaps they'll start using retinal scans or fingerprint detectors on the steering wheel. It should be a good theft-prevention model, until you try letting your designated driver take you home and it won't start. And then it won't start for you because you're drunk.
Maybe we'd best forget the whole idea.
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On Tue, 02 Jan 2007 22:06:04 -0800, jim beam

Well, I'm sure they have improved somewhat since they made the one for my '98 Ody, but I would be surprised if they now know in which gear I want to do compression braking. I'm pretty sure they don't downshift in anticipation of me wanting to do hard acceleration two seconds before I touch the gas pedal. How does it know that, even though I am doing a steady 40 mph, I want to stay in second gear to be ready to make a move in traffic? Does it know not to downshift just before we crest the hill? For my Ody, I would be happy if it just didn't downshift when I hit Resume on the CC 4 mph below the target speed. I would hope they have at least fixed that.
Bottom line is they are OK for average (or worse) drivers in light traffic. But I definitely don't like them in heavy city traffic and they just don't belong in any sports car IMO.
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Gordon McGrew wrote:

no, they provide a handy little lever that allows you to take care of that by hand.

see above.

press the brake and you'll find out. they have grade control logic. increasing speed + zero gas = downshift.

tell that to porsche - last i heard, their autos were faster than their sticks.
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On Fri, 05 Jan 2007 18:00:46 -0800, jim beam

Right, you can force the downshift or hold the gear manually but a. then its not automatic and b. it is clumsy to shift especially on the steering column.

My comment is that the transmission downshifts when I dont want it too, i.e. just before cresting the hill when I would manually just stay in the higher gear for a few more seconds.

That is because most Porsche buyers are people who want to show off how rich/cool they are and don't really care about driving it or even know how.
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Gordon McGrew wrote:

but don't say it can't hold a gear because it can! you can leave it in full auto or you can manually over-ride - the ultimate in choice. i agree with you about column shifts however - i can't stand them.

dude, you said auto's couldn't hold a gear - they can. and grade logic means they select the right gear, certainly a good deal better than some of the individuals that pop up here from time to time putting their sticks into neutral and coasting down hills. modern autos are not only programmed to shift right, they also learn what the driver likes.

eh? how does criticizing [without basis] driver skill address the ability of a computer-controlled transmission to shift faster than a stick? makes no sense.
bottom line, you're welcome to drive whatever you want, but don't criticize autos on the basis of fud - it's simply not justified.
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On Fri, 05 Jan 2007 21:48:16 -0800, jim beam

Sorry, I misread the post. I thought you were saying that the ATs were *selling* faster than the MTs.
My preference for MT is not based on how fast it shifts but rather the ability to integrate the shifts seamlessly into driving. This requires decisions based on information that the computer cannot possibly know. May not matter much for a minivan, but it is fundamental for a sports car.
The problem with most (virtually all) ATs is that they are biased toward automatic operation and discourage manual operation. Also, I don't particularly care for the slippage of the torque converter. I understand that VW has a paddle shift AT that is actually built like an MT. This has potential if the AT function can be completely disabled, i.e. it never makes a shift without a command from the driver. (Not that I would buy a VW under any circumstances.)

fud?
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Gordon McGrew wrote:

that's your perception. unless you've driven a modern auto, especially a sports auto, you're just making uninformed assumptions and using them as your basis for criticism.

how? my auto has the shift in exactly the same place as where the stick would be. i see no difference. the transmission even has a no-lock gate between 3rd & 4th [commonest manual override] especially so you /can/ flip up and down at will.

eh? what "slippage" is that? how does its mechanical function differ from a clutch [other than it has a much better efficiency range and is much smoother of course]?

as are a lot of the euro "autos".

dude, have you ever driven an auto? you have pretty much full control over everything except clutching action - except for the fact that it won't let you select wrong gears of course.

fear. uncertainty. doubt. if there is no technical argument against something, people resort to fud.
here's another nugget for you - automatics are banned from f1. like certain types of ground effects, they gave too much advantage to the [better funded] teams that had them. the compromise is paddle shift, but even then, interpretation of the ban has been taken to the limit since a lot of the control functions are still automatic.
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On Sat, 06 Jan 2007 11:16:04 -0800, jim beam

If you put it in 4, will it ever downshift into 3 by itself? When you shift into 3 does it effectively double clutch?

Well, as you point out, I don't have any experience with modern high end luxury cars, but I note that at least more modest cars generally have a significantly greater 0-60 speed and a lower mpg rating. Since they now mostly have five gears, I would assume that means they are slipping. Actually, the slipping is partly by design, the so-called torque multiplier effect. Basically, if you are cruising along and you give it a little gas, but not enough to force a downshift, you will see the rpms jump up immediately.
The ultimate "torque multiplier" is a CVT. A lot of people don't like them at all, but others say they get used to it. (The perception problem is so bad that some manufacturers program virtual gears into them thereby defeating the chief advantage of the CVT.) I only rode in one CVT car, a Nissan luxury sedan in Japan and it wasn't bad in that application. He drove it fairly aggressively too - we hit almost 180 kph on the expressway. I would like to try one of these. I don't know if I would like it or not.

Will it let you start out in 5th gear? Not that I want to do that, but the point is I don't like it downshifting or upshifting without my command.

Well, I would certainly prefer an MT to the AT in my 98 Ody, but of course that was not an option.
Perhaps newer, high dollar vehicles are better set up for manual shifting, and have fewer compromises but then that raises the point: Why not just have an MT? They are cheaper, more durable and I like the way they work just fine. For my purposes and preferences, I see no benefit to an AT whatsoever.
I presume I will never again be able to buy a large, cargo carrying vehicle (eg. my old Volvo 245 station wagon) with an MT so I assume I will have to go with 2007 technology sooner or later. I will let you know what I think.

I would first point out that torque converters are not banned AFAIK, but they are not used either. I would be curious to know whether and how ATs would be used in F1 if they were not banned. I can imagine the programming: if rpm >= redline then upshift, if downshift RPM < redline then downshift. The situation is a little different on the road and the technology is bound to be different and more compromised. I seem to recall Ferrari had an AT at one time in F1. I dont' recall if it was a clear advantage but I do recall that on a couple of occasions it decided to downshift into 2nd when it should have been in 5th. That was exciting. Not relevant to the argument but an amusing story. It may have been an early paddle shifter rather than a true AT
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Gordon McGrew wrote:

yes, absolutely. it does it on "kickdown" acceleration /and/ it does it on braking. not gentle braking, but harder braking.

pointless exercise on an automatic. but even then, on the modern autos, in conjunction with electronic throttle, yes, the engine revs /are/ meshed to the gear on shift.

there's no slipping unless the lock-up clutch is released. see below.

yes, that's what a torque converter does.

that's because the lockup clutch is released to allow more torque. more flexibility than a stick where you'd have to shift.

that's different - it's not a torque multiplier. if is however a great way of achieving absolute optimum gear for all conditions.

absolutely! i drove a "real" cvt one when i was in europe years ago, and yes it is /real/ weird at first. but it's amazing how much you can get out of a small 2-cylinder engine when it's got perfect gearing. quite fun! this particular model had 2 independent drives too, so not only did you have optimum gearing, you had limited slip diff benefits in snow & ice too. http://www.ritzsite.demon.nl/DAF/DAF_cars_p2.htm

if you're not used to traditional automatics, the transition is easy. if you're used to traditional autos, its weird for a few minutes because it doesn't "shift", but beyond that, they're actually very impressive.

no, but it'll start in 2nd. mine will anyway. useful in snow.
regarding shifting, it'll shift down any time on command, providing doing so doesn't over-rev the engine - it won't let you do that. regarding up-shifting, you can hold it back until you're ready, and even then, it'll wait until it's certain you mean it - if you have your foot down. if you're not driving hard, it's academic.

i used to think that. then i had a knee injury that prevented me driving a stick for some months, so i bought an auto. and every time i've driven a stick since, it's been a real chore. that was nearly 20 years ago. it may be that there's some bad autos out there, but the way i have my civic set up [the shift pattern is adjustable], the shift points are pretty much dead on where i'd have them manually, and for other stuff, i over-ride.

correct - they're heavy.

i think in due course, semi autos will replace sticks. at least in sports cars. they offer faster, more accurate shifting, and computer control knows more about the potentials of the system than the driver does a lot of the time. a friend has a tiptronic carrera - hold the shift lever and put your foot down, and it'll select the lowest gear for the speed to give fastest acceleration, and you can revert to auto from there so it shifts up through in the fastest possible time. trust me - it's fun!
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On Sat, 06 Jan 2007 14:33:58 -0800, jim beam

It is not a bad thing, I just don't care for it. If I want to downshift, I can do that. If I don't want to, I don't like the car doing it on its own.

That is what I mean. I figured they had fixed that aspect which is the worst part of the older ATs.

But that is the slippage. The engine speeds up races up ahead of any change in vehicle speed. It is like a slipping clutch. As for more torque (horsepower really) a lot of that is eaten up by the inefficiency of the torque converter. On cars where you can get a MT or AT with the same engine, the MT is almost always faster and gets better mileage.

Neither is the conventional AT, it just has a clever design to let the engine speed up ahead of the vehicle speed without shifting. It is basically like a limited range CVT.

I agree that it has a big theoretical advantage, especially compared to a conventional AT.

That was the original CVT. Do you remember who offered the first CVT in the US. (I don't think they ever sold the Daffodil here.)

Again though, I am not sure they are any faster or more efficient than a good MT. Consumer Reports tested the Versa with MT and with CVT. The MT version was 0.6 seconds faster to 60 and got one more mpg. (And CR panned that MT.) They also tested MT and (conventional) AT versions of Fit, Rio, Accent and Yaris. In each case the MT was 2 - 3 seconds faster and got 2 more mpg, so the CVT was clearly better than an AT but not as good as even a mediocre MT, at last on raw numbers.
And yet, there is hardly a proliferation of CVTs on the market. Most of them seem to be on hybrids in fact.

I appreciate that many people prefer AT, and if you have a bad knee, there isn't much choice. But I really enjoy driving the MT. I haven't encountered an AT yet that I could actually say I enjoyed, but I certainly haven't driven many new ones.

It was a computer glitch. As they say, to error is human. To really foul things up requires a computer.

I am open to that, but it has to come down to Civic level before it will have any relevance to me. I am sure that a Porsche would be fun no matter what kind of transmission it has.
BTW, you might want to review my post in this thread from 2005:
http://tinyurl.com/ygpvay
I had no idea they would work that way, it just seemed like the logical way to do it.
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Gordon McGrew wrote:

why not? it's just like you'd have on a stick.

but i don't understand the problem - what's wrong with it? engines are not perfect across all rev ranges - why not let a computer manage the efficiency curves - for that's what's happening.

how is a slipping clutch more efficient? [it's not.]

not so with the modern autos. and that's one of the big things about honda autos - it's basically a standard transmission with clutch packs instead of synchros. inherently more efficient than planetary gears.

no dude, they're totally different. "torque multiplier" is something a torque converter can do - hence its name. everything else is ratio control, be it continuously variable or discrete.

compared to /any/ transmission. there are mechanical efficiency issues with the friction interface, but that is more than outweighed by ratio flexibility and ability to keep the engine at its most efficient.

subaru?
well, the daf was only 650cc iirc, and 0-30, that wasn't much to touch it.

that depends on the management system. the modern cvt's "simulate" gear shifts which is the dumbest damned thing since it's not utilizing the inherent benefit of the system! on that basis, i'm not surprised.

that's consumer and mechanic inertia - nothing to do with benefits or reliability. trust me on that one - i've driven the daf for an extended period and it's a great system.

indeed.
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Interesting discussion I started here, I guess....!
I've driven the CVT in an Audi A4 loaner and thought it was weird at first (as someone else noted). But it also had 'sport' settings where it would 'shift' thru seven 'gears'. There are more CVT's out there than you think - off the top of my head, I can think of the Audi (A4 non-quattro auto models), Ford Freestyle cross-over, and Nissan Altima, Murano, Maxima and Versa.* I think some version of the Ford Five Hundred has it as well. So, they are becoming more popular.
The best compromise seems to be the automated manual transmissions - they are a true manual trans with an automated clutch. No torque converter. ( http://en.wikipedia.org/wiki/Direct-Shift_Gearbox ) Audi's DSG is commonly considered the best example, although BMW has one (whch regularly gets panned for poor auto shifting). Porsche may have one as well. I've driven the DSG and it is excellent, very fast shifting and a decent auto mode as well. But I still prefer a conventional manual transmission.
For the Ody, I'm prefectly happy with an automatic.
*Oh, Wiki has a list of CVT equipped autos world-wide.
* Audi A4 2.0/1.8T/2.4/3.0/2.5 TDI * Audi A6 2.0/1.8T/2.4/3.0/2.5 TDI * Dodge Caliber * Fiat Punto 1.2 L * Ford Escape Hybrid 2.3 L 4 cyl * Ford Five Hundred 3.0 L 6 cyl * Ford Focus C-MAX 1.6 L TDCi 110 PS * Ford Freestyle 3.0 L 6 cyl * Honda Civic HX 1.7 L 4 cyl * Honda Civic Hybrid 1.3 L 4 cyl * Honda City 1.5 L * Honda HR-V 1.6 L * Honda Insight 1.0 L 3 cyl * Honda Jazz 1.4L / Honda Fit 1.3 L/1.5 L * Hyundai Azera 3.8 Lambda * Hyundai Sonata 3.3 Lambda * Jeep Compass 2.4 L * Lexus GS450h 3.5 L 6 cyl * Lexus RX400h 3.3 L 6 cyl * Mercedes-Benz A-Class
* Mercedes-Benz B-Class * Mercury Montego 3.0 L 6 cyl * Microcar MC1/MC2 505cc 2 cyl diesel or petrol * Microcar Virgo 505cc 2 cyl diesel or petrol * Mitsubishi Colt 1.5 L MIVEC 4 cyl with INVECS-III CVT (Asian-Oceanian version only, 72 kW) * Mitsubishi Lancer 1.6 L/1.8 L MIVEC 4 cyl with INVECS-III CVT (Asian version only) * MG F/MG TF 1.8L * BMW MINI One and Cooper. * Nissan Altima (from 2007) * Nissan Cube * Nissan Maxima (from 2007) * Nissan Micra 1.0 L/1.3 L * Nissan Murano 3.5 L * Nissan Primera 2.0 L * Nissan Sentra (from 2007) * Nissan Serena 2.0 L * Nissan Skyline 350GT-8 * Nissan Tiida / Versa * Opel Vectra 1.8 L * Rover 25 * Rover 45 * Rover Streetwise * Saturn ION Quad Coupe (2003-2004) * Saturn VUE 2.2 L AWD (2002-2005), 2.2 FWD (2002-2004) * Subaru R1 * Subaru R2 * Subaru Stella * Toyota Highlander Hybrid 3.3 L 6 cyl * Toyota Camry Hybrid 2.4L 4 cyl * Toyota Prius 1.5 L 4 cyl
Dan D '04 A4 1.8Tq 6-speed
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I would really prefer that Honda would make a Volvo 240 wagon with performance suspension and an MT, but I have pretty much given up hope.

See my comments below. Few of these are currently available in the US,. If you eliminate the hybrids, I think there are only about three. Partly this is due to most CVTs being designed for small engines.
Most CVT designs seem to be reliable and the efficiency improvement is significant compared to conventional ATs. I really think that the test drive turns off a lot of buyers because it is so unconventional. Honda is apparently selling a "7-speed CVT" - talk about an oxymoron. This is a sure sign that buyers are turned off by normal CVT operation. Hybrids may be the thing that brings CVTs out of the closet.
See comments below.

The only US Civic currently offered with a CVT is the Hybrid.

I haven't heard of a Honda City in a long, long time. Are they still sold?

Never sold in US.

Discontinued - will probably be replaced.

No CVT in US market.

I am a little skeptical of those dates. I didn't think they were on the market that long before it was discovered that every single one of them breaks. And GM wonders why it is going out of business. LOL

Subaru Justy (probably equals one of above models) was sold with a CVT in the US for a few years in the 90's. Subaru hasn't sold a CVT in the US since.

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On Sun, 07 Jan 2007 15:20:11 -0800, jim beam

Not sure I understand. My GS-R never downshifts on its own.

It is just a personal preference. I like the engine to be positively coupled to the wheels.

No, I understand that (unlike a slipping clutch) there is a benefit to the slip designed into the AT. I just don't like the feel of it and the benefit is more than eaten up by the inefficiencies that come with it.

Looking at the differences between the ATs in the econo cars tested by CR, Honda looks about as good as the other ATs (except for the CVT.)

OK, explain it to me. My understanding is that it is just a trick to get the engine running at a slightly higher rpm to produce more power. Kind of like a mini downshift. All car transmissions are torque multipliers. They take high rpm/low torque and turn it into low rpm high torque. If it were perfectly efficient, the power output would be equal to input but of course it is always less. No way to get more power out unless you put more power in, i.e. run the engine at higher rpm.

The why doesn't the Versa with a CVT get better mileage or accelerate faster than the Versa with an MT? Unfortunately, there are few cars which allow you to directly compare CVT vs. MT.

That is what I recall. The car was called the Justy.

I think the Honda 600 would have blown its petals off. ;-)

Does the Versa do that? CR didn't mention it.

Maybe. I would gladly trade the AT in my Ody for one if it was proven reliable. Not all are. The on in the Saturn Vue was a disaster, but I guess you have to expect that from GM. The Japanese units don't seem to have any problems.
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