For a number or years, automatic transmissions have been mostly four speed.
Now I'm seeing five and six speed, plus Nissan Maxima has a constant
velocity on the '07 models (shades of Turboglide?)

In theory, the more speeds the smoother acceleration and ease of staying in
a power range of the engine. In practice though, does it really make
difference? Any thoughts on what is "best"?
--
Ed
http://pages.cthome.net/edhome/

Edwin,

In theory, the best would be an electronically controlled CVT,
where you have infinite ratios available and, by sensing engine load,
throttle position, road speed, etc. get a "perfect" match of engine
power to need, also taking into account fuel economy and emissions.

Needless to say, such a system would be complex and expensive. I'm
glad to see Nissan bite the bullet and try that sort of system in the
Maxima (though I'd not want to be one of the "test subjects" to try it
out in the real world unless they'd guarantee that transmission for
say 150K miles).

As far as conventional multiple speed transmissions, you have a
trade off of added cost, complexity, the added weight of the
additional gearsets and servos required to operate it as you increase
the number of speeds VS the improvement in mileage and emissions the
additional transmission gears provide. Modern electronics makes it
easier: a silicon computer works much quicker and with less complexity
that a hydraulic one can (electrons can move much faster than
hydraulic oil, valves and springs).

One real-world example I could use is to compare the operation of a
GM 4T60 with a 4T60E (drive a 1992 Buick Regal, then try a 1993: about
the only mechanical difference between those 2 cars is the 1992 has a
4T60, which has no electronic control except converter clutch lockup,
the 1993 has a 4T60E which has electronic controlled shifting) -
gearsets and such are the same, but the 4T60E operates sooooooo much
better. The later 4T65E better yet - even more of the hydraulic
controls where replaced by software in the PCM.

. Also, the "hype factor" has to be taken into consideration as well
- all the auto makers, both foreign and domestic, are in a game of
"keeping up with the Jonses". Those marketing folks always want new
and better things to tout and hate the idea that they don't have what
the other guy is offering (or maybe something even better).

The old Chevrolet TurboGlide was a great idea conceptionally, but
suffered in the execution due to the state of the art available in
1958. It was highly complex internally and a real bitch to work on.
I've always wondered if the concept might fare better given modern
computer-aided design technology, but I still believe that CVTs are
the wave of the future.

Regards,
Bill Bowen
Sacramento, CA


"Edwin Pawlowski" <esp@snet.net> wrote:

>For a number or years, automatic transmissions have been mostly four speed.
>Now I'm seeing five and six speed, plus Nissan Maxima has a constant
>velocity on the '07 models (shades of Turboglide?)
>
>In theory, the more speeds the smoother acceleration and ease of staying in
>a power range of the engine. In practice though, does it really make
>difference? Any thoughts on what is "best"?

"William H. Bowen" <wh_bowen@sbcglobal.net> wrote in message
news:u6tlc2lpscgks4mioadjqhu7179l5d95l1@4ax.com...
> Edwin,
>
> In theory, the best would be an electronically controlled CVT,
> where you have infinite ratios available and, by sensing engine load,
> throttle position, road speed, etc. get a "perfect" match of engine
> power to need, also taking into account fuel economy and emissions.

I pretty much agree with you, Bill. Making a durable CVT is a bit of
a challenge, but I think of it in the same light as making a durable
4-wheel drive system. In the old days, 4-wd systems existed and were
desirable but they wore out quickly, they used extra fuel, and needed
a good bit of service. Now, they have largely been tamed.

Autotrannies can get better in just the same way, and they are much
better today than they used to be , except for the occasionally runs of
units which have not been well developed by the manufacturers in their
haste to market.

My next car is going to be a manual transmission Volvo, and that
doesnt disappoint me either. ( A new development, for me. I am coming
out of retirement for a few years of foreign service, and this car is
already
leased and ready to go.) I will continue, I hope, to be able to keep in
contact via these groups, and will let you know how it does.

"Edwin Pawlowski" <esp@snet.net> wrote in message
news:4pCyg.137493$dW3.36616@newssvr21.news.prodigy .com...
> For a number or years, automatic transmissions have been mostly four
speed.
> Now I'm seeing five and six speed, plus Nissan Maxima has a constant
> velocity on the '07 models (shades of Turboglide?)
>
> In theory, the more speeds the smoother acceleration and ease of staying
in
> a power range of the engine. In practice though, does it really make
> difference? Any thoughts on what is "best"?

The very same question ran through my mind lately Ed. The Nissan commercial
brought it forward in my mind. CV transmissions are certainly nothing new
and they are a pretty proven technology. I'm not sure if the technology has
proven itself to scale up to car size applications but I suppose the Nissan
will show whether it does or not. If I'm not mistaken, isn't there a Honda
that uses CVT also? Seems to me that Ford tried this not so long ago also.
It's certainly a much more simple transmission design.

--

-Mike-
mmarlowREMOVE@alltel.net

"William H. Bowen" <wh_bowen@sbcglobal.net> wrote in message
news:u6tlc2lpscgks4mioadjqhu7179l5d95l1@4ax.com...
> Edwin,
>
> In theory, the best would be an electronically controlled CVT,
> where you have infinite ratios available and, by sensing engine load,
> throttle position, road speed, etc. get a "perfect" match of engine
> power to need, also taking into account fuel economy and emissions.
>

Let's talk about that some Bill. Since CVT is all about centrifugal force
it is easier to keep the proper "gear ratio" simply based on the load placed
on the engine. I'm not sure we would need as many of the electronic
monitoring and control functions since the tranny is more self regulating
than a multiple speed gearbox.

I'm wondering what the thing actually looks like inside. In my imagination,
I'm seeing this large-ish snowmobile belt humming away...

--

-Mike-
mmarlowREMOVE@alltel.net

AWD Ford 500s and Freestyles currently have a CVT tranny.

mike hunt


"Mike Marlow" <mmarlow@alltel.net> wrote in message
news:c5647$44cb4887$471fb97a$25586@ALLTEL.NET...
>
Seems to me that Ford tried this not so long ago also.
> It's certainly a much more simple transmission design.
>
> --
>
> -Mike-
> mmarlowREMOVE@alltel.net
>
>

High winding engines are more fuel efficient and develops more HP. The Japs
like to advertise the HP their engine produce. The problem with that
however is the torque band and the HP band are too far apart. It works fine
when one has a manual tranny and uses the gears to stay on the proper torque
band but in the US most buyer prefer automatic trannys. If one does not
keep their foot in the throttle, the vehicle dies on the grades. That is
why the 4 cy Camry is a dog on the grades. To improve the situation the
answer is more gears or a CVT. Many say the 500 is under power with the
CVT. It is not, IF driven properly. When starting out with a CVT, or
climbing a grade, one must floor the throttle to take advantage of the
tranny ability to stay in the torque curve. If one simply uses part
throttle, it is like starting out in a higher gear with a manual tranny.
The Nissan commercial is deceptive. It shows the RPMs climbing, when it
actually would be at it peak the way the driver is driving.


mike hunt




"Edwin Pawlowski" <esp@snet.net> wrote in message
news:4pCyg.137493$dW3.36616@newssvr21.news.prodigy .com...
> For a number or years, automatic transmissions have been mostly four
> speed. Now I'm seeing five and six speed, plus Nissan Maxima has a
> constant velocity on the '07 models (shades of Turboglide?)
>
> In theory, the more speeds the smoother acceleration and ease of staying
> in a power range of the engine. In practice though, does it really make
> difference? Any thoughts on what is "best"?
> --
> Ed
> http://pages.cthome.net/edhome/
>

CVTs have been around in cars for many years. The DAF used a CVT in the
sixties. They have been around at least since the thirties, on stationary
engines, that drive machinery. It is only recently that technology as made
it possible to use a CVT on engines that operate at higher RPMs


mike hunt


"William H. Bowen" <wh_bowen@sbcglobal.net> wrote in message
news:u6tlc2lpscgks4mioadjqhu7179l5d95l1@4ax.com...
> Edwin,
>
> In theory, the best would be an electronically controlled CVT,
> where you have infinite ratios available and, by sensing engine load,
> throttle position, road speed, etc. get a "perfect" match of engine
> power to need, also taking into account fuel economy and emissions.
>
> Needless to say, such a system would be complex and expensive. I'm
> glad to see Nissan bite the bullet and try that sort of system in the
> Maxima (though I'd not want to be one of the "test subjects" to try it
> out in the real world unless they'd guarantee that transmission for
> say 150K miles).

> Bill Bowen
> Sacramento, CA
>
>

"Mike Marlow" <mmarlow@alltel.net> wrote in message
news:c5647$44cb4887$471fb97a$25586@ALLTEL.NET...
>

> The very same question ran through my mind lately Ed. The Nissan
commercial
> brought it forward in my mind. CV transmissions are certainly nothing new
> and they are a pretty proven technology. I'm not sure if the technology
has
> proven itself to scale up to car size applications but I suppose the
Nissan
> will show whether it does or not. If I'm not mistaken, isn't there a
Honda
> that uses CVT also? Seems to me that Ford tried this not so long ago
also.
> It's certainly a much more simple transmission design.
>
> --
>
> -Mike-
> mmarlowREMOVE@alltel.net

There have been a number of CVT applications around, and Honda is one of
them, I believe.

One of the first designs I saw commercialized was the Dutch DAF unit, years
ago. DAF was
never popular over here, and the application was, IIRC, a rather low powered
one, so I can't
speak with any real experience to their durability.

I am not convinced yet that they are as durable as we, as consumers, will
want, especially
in the higher horsepower versions. And to say that they are simple might be
misleading as well.
But I do think that new designs and materials will eventually evolve that
will make them
attractive and less of a gamble.

Thanks for the interesting replies

> Ed
> http://pages.cthome.net/edhome/
>