The new C6 sounds like a great car, but it also sounds like those of us who need an auto tranny are really being ignored- same 'ole 4 speed, no paddle shifter. In other words, everything in the entire car got upgraded except the transmission. Or did I miss something important??? :confused:

 

Nope. Except they've probably built it to handle 400+HP now.

Solution: Buy a 6spd or install a manual valve body :yesnod:

 

It appears that the 2005 C6 will get a 4L65-E
http://www.superchevy-web.com/tech/0311sc_4l65e/

The new 6-speed automatics don't go into production until MY2006.
http://www.sae.org/automag/techbriefs/12-2002/ (Scroll down to near bottom)
http://media.gm.com/division/2004_pr...rwd_6speed.pdf
http://waw.wardsauto.com/ar/auto_gm_plans_speed/

I sincerely hope that the 4L65-E is pitched in MY06 and replaced
with the X15R. However, I do not know if this will actually happen.

 

with more cubes and torque you will not need any more speeds except to increase fuel milage with more overdrive. GM is cutting weight from the C-6 and more gears = more weight. if they get enought HP and get the weight lower we may see the old 2 speed powerglide come back. look how it works in drag cars and even the guys with the LS-1 F bodies are putting in 3 speed THM 350s and 400s to get better drag strip performance :chevy


[Modified by clem zahrobsky, 2:02 PM 11/27/2003]

 

Clem,

Many people on this forum dismiss 6-speed ATs.

A six-speed AT offers better mileage and greater performance than
a four-speed automatic. The mileage benefit is in being able to better
match the actual engine speed to the optimal engine speed. The same
thing happens for acceleration but you simply redefine "mileage
optimal" to "performance optimal." You can clearly see this in GMs
document below
http://media.gm.com/division/2004_pr...rwd_6speed.pdf

The identical comments may be found in countless technical articles, technological
surveys, and patents. Aside from potentially increased cost, they get you better
mileage, better acceleration, and generally do not increase weight. I don't understand
how people can be against moving to a 6-speed AT. The new X-13R, X-14R, X-15R,
and X-16R are going to be a serious improvements over the 4L60-E, 4L65-E,
4L80-E, 4L85-E. Above and beyond the change from 4 to 6 forward gears, we'll
also ( I think ) get improved torque converters.
http://media.gm.com/division/2004_pr...train/advanced torque converter.pdf
(You'll have to enter that address yourself because of the spaces at the end. )

Take a look at pages 12-13 of ( http://books.nap.edu/html/cafe/ch3.pdf ).
It is part of a bigger document ( http://www.nap.edu/html/cafe/ ).

I suspect that money got tight at GM and the 6-speed ATs were held up until the
2006 model year. Beyond 6-speeds, the sky is the limit
http://forums.corvetteforum.com/zerothread?id=699595

I'd love to see a high-torque 7-speed AT offered on the Z06 or the ZL1
but that's me dreaming.

 

i would think if the gears as they shift put you in the correct part of the power band you would get max acceleration. with a narrow power band i can see the need for5, 6 or 7 speed trannies to keep the engine on the "pipe" the torque curve of the corvette engine is pretty flat so i would think as long as you end up in the correct part of the power band you would get max acceleration. a friend of mine drag races a 400+ cu in SBC in camaro and the car is quicker with a 2 speed PG than with a 3 speed THM both set up for drag racing. JMHO :chevy

 

I haven't completely thought this out but this is the way I
look at it. The goal in acceleration is to change the kinetic
energy (KE) of the vehicle as quickly as possible. For simplicity,
assume the rate at which the engine deposits kinetic energy
into the vehicle is constant otherwise we would descend into a
million subtle distinctions. Hence, we want to maximize the moment
by moment power that is actually feed into the vehicle's kinetic
energy. That means the goal of the transmission is essentially
to keep the engine on it's hp peak. If you have a broad torque
band and you have an A4 that lets the rpm's drop well below
the hp peak then you are depositing a minimal amount of KE
into the car. An A6 will keep the rpms closer to the hp peak
and although the torque applied to the input shafts of the A4
and A6 may be the same, the rate of energy being applied to the
vehicle is quite different.

There is a seeming contradiction here. It is important to distinguish
between engine torque and rear wheel torque (RWT). If a C6 is accelerating
at 70 mph with an A6 at, say, 5000 rpm or an A4 at 4000 rpm then the
torque multiplication factor means the RWT of the A6 car will be
higher than the A4 car and the acceleration rate will be higher too.

Obviously, drivetrain losses and traction play a part here too
because they effect how much of the engine power can be spent
on changing the KE of the vehicle.

 

the more parts in rotation in the drive train the slower the acceleration. that is why we remove 1 st and 2 nd gear from 4 speed trans for circle track cars because they accelerate faster with less parts in the trans. anything that adds extra weight to the rotating mass,crankshaft,flywheel,extra gears in the tranny,ring gear weight,wheel and tire weight and even the axle weight slow down acceleration. that is why we used convertorless power glides in circle track cars because the internal weight of the trans parts is less than a 4 speed even with 1 st and 2 nd gears removed. also the flexplate weights less than any flywheel and clutch combo. the biggest killer in the auto is the weight of the convertor full of oil. i have heard the GM has a convertorless auto that uses servos motors some how to eliminate the torque convertor.

 

I'm confused. On one hand, I can see that the transmission could keep the revving closer to the engine's peak power range.

On the other hand, the downfall of automatic transmissions is the time it takes to shift them. Wouldn't more shifts mean slower acceleration? :confused:

 

Downfall? I think you've got it wrong. The one thing that autos offer is quick shifts (ie you never have to go through neutral to get to the next gear and lose as much time/revs). :cheers:


[Modified by Sanctuary, 8:35 PM 11/28/2003]

 

[QUOTE]On the other hand, the downfall of automatic transmissions is the time it takes to shift them. Wouldn't more shifts mean slower acceleration? :confused:

Downfall? I think you've got it wrong. The one thing that autos offer is quick shifts (ie you never have to go through neutral to get to the next gear and lose as much time/revs). :cheers:

[QUOTE] :withstupid:

 

In defense of GDP, one should distinguish between the time it
takes a transmission to change gears once and the total time spent
doing all gear changes. A 4-speed AT will probably shift two
or maybe three times in a 1/4 mile run (what's top speed of
a 2.73-rear C5 in third gear?). When you're shifting, power
is not being deposited in the vehicle and the time integral
of the power delivered is reduced. I suspect that a 6-speed
AT will make one more shift in the 1/4-mile than a 4-speed
will. However, I think the new 6-speed ATs will handily
beat similar A4s.

 

What I can't wait to see is two C6's at the starting line; one
with a 6M and one with a 6A (2.73 or 3.15). I wonder who would
win. I bet the 3.15-6A would beat the 6M.

 

all a stock C-5 A-4 needs to beat a stock C-5 6 speed in the 1/4 mile is a looser convertor. a $200 GM rebuild convertor from a V-6 will help a lot. :chevy

 

Uhhhh...but the C6 is getting an A4, at least for 2005.

 

Being in or close to the peak power is always better than not. More gears allow you to be around the peak power more often.

The current auto has really only 3 gears and an "overdrive" 4th. Overdrive is worthless in auto or manual unless you're just cruising. It is well documented that an auto C5 is slower than its manual counterpart. The only way a 6M is slower than an A4 is if the driver couldn't drive.

I agree a 6 speed auto with similiar gearing would probably give most average 6M drivers fits. However, I still don't like going into a corner and hoping the shift logic doesn't decide to kickdown out of nowhere and send the car into a tailspin. This is where a manual shines...the control you get by being in the gear you want at the time you want.

 

Clem,

Throughout this thread, I have been talking about well rounded
transmissions and not one that is tuned for the quarter mile and is
useless otherwise. What kind of heat does that slip-monster generate
during a run anyway.

Changing the subject a bit ...

I don't think it's going to be long before the combination of 6-8
forward gears in an automatic with a big computer will outperform 99% of
drivers 99% of the time. That goes for the quarter-mile and Nurburgring
too.
http://media.gm.com/division/2004_pr...ion_launch.pdf
http://media.gm.com/division/2004_pr...train/advanced torque converter.pdf

( you'll have to manually enter this because of the spaces )


To the people who insist that having a manual transmission is the true testiment
to their alpha male status, reality will be a tough pill to swallow.




[Modified by Runge_Kutta, 10:30 PM 11/28/2003]

 

"Uhhhh...but the C6 is getting an A4, at least for 2005."

Yes, I would have thought that was brutally obvious from the thread,
particularly my first comment on this thread, so I must have been speaking
hypothetically.

 

it is a lock up convertor so on the road heat is not a problem. it takes the stall speed up to about 2200 flash RPM and makes a big difference in the SOP feel to the car. just like reving up a 6 speed and dumping the clutch. :D this is a very cheap hop up for any V-8 GM car. :chevy

 

"Along with many other automotive engineers, I am well aware that an automatic transmission does not rate with enthusiasts. A number of years ago in a S.A.E. paper, I stated my preference for an automatic transmission for racing cars. Someday an automatic transmission will meet the requirements".

Zora Arkus-Duntov 1955

I had the pleasure of meeting Zora Duntov several times here on Maui in the mid-80's. He lived here in Kula for a time and would come screaming by in his 74' Big Block with a big grin plastered on his face. I think he would be very pleased with the progress of automatic transmissions in that his "someday" may be coming up shortly.... :D