vetteLT193

Will the Z51 cars be able to do top speed in 6th of right around 200? It seems like it could... I wonder if GM is going to shoot for another 24 hour record with it.

jschindler

I appreciate your candidness. I think the incredible low end torque they are claiming is going to be the answer. With seven gears to work with, I have to believe that GM got it right. Of course, we all know that there will be folks that change the gearing just because they can. Some folks believe in the adage that "friends don't let friends drive stock".

travisnd

No.... each transmission would hit 200 in 5th.

theseal

Yes, I was getting a little cute. You know, thinking like an AMERICAN. The Texas Transporation Code (and most other states) defines speeding as follows;

Sec. 545.351. MAXIMUM SPEED REQUIREMENT.

(a) An operator may not drive at a speed greater than is reasonable and prudent under the circumstances then existing.



with respect to 'speed limits' as most americans mistakenly think of them,

Sec. 545.352. PRIMA FACIE SPEED LIMITS. (a) A speed in excess of the limits established by Subsection (b) or under another provision of this subchapter

[i.e. the 'posted speed' you see on the sign which is abused for illegal revenue generation by state and local governments]

is prima facie evidence that the speed is not reasonable and prudent and that the speed is unlawful.

In other words, the posted speed gives cops an excuse to try to fine you, and if you are so abused, then a jury decides whether your speed was 'faster than reasonably prudent.'

If you are a brainwashed sheep, you think the posted speed should define your freedom. If you think like an american, you travel at reasonable speeds to respect the safety of others, and on most interstates, 100 is within this range in a modern car if you're paying attention, on dry roads, with good visibility.

Of course, as a practical matter, like in many other areas of government these days, many local judges will lie and break the law to try to keep your illegally generated fine. And of course, many american jurors are brainwashed sheep.

So, you have to weigh your personal values and desire for free and rational living against your tolerance for harassment by government.

Back to the transmission issues, with the old trans, you are at 2000 in 6th cruising at 100. Now you are at 1800 in 7th.

Is swinging 11 pounds more weight around all day, with the associated cost and durability charges, worth 200 rpm? I would say not.


I am not sure what your other objections were; my estimates are roughly correct: 3rd appears to go to about 115, close to a 1/4 trap speed.

Why would you want 4 more gears after the quarter mile, if not to dip even lower for gas mileage at cruising speeds?

In my mind, good spacing to finish the quarter at redline in 4th is most appropriate, with top speed in 5th, and 6th for an overdrive.

That gearing happens to work really well on most tracks, as well as autocross, and is very livable in the street.

Anything else is less than ideal.

85scott

And I really like the gear ratios in the base trans. I remember some of the 1980's cars I had with a stupid low 1st gear and bad traction to boot. Made 1st gear totally useless. And that was even with half the horsepower in a Corvette now.

85scott

I don't believe there should be a speed limit either. And every speed bump should be torn down. Every carpool lane re-opened for all traffic to use. And the outside lane for passing-only should be something that's much more promoted than it is now.

The idea is to keep traffic moving as freely as possible.
Traffic lights & stop signs should be built with prudence in mind also.

johnglenntwo

The 7th gear is really a place holder in the smaller Vettes. Think how well it would have worked out in the ZR1 and then translate that over to the Z06. The Z06 lost torque and quickness up top because it didn't have the shorter 5th gear.

OBSSSD

1 reason - cost

They simply added a lower 7th gear to the existing transmission along with DOD to get better fuel economy, but the problem is they sacrificed almost 10% of the top end power of the motor to do it

Trackaholic

Your Texas code and CA code is essentially the same, however I don't quite understand your interpretation.

Prima Facie means by definition that anything above the posted speed in any condition (even perfect condition) shall not be considered reasonable and prudent. In effect, the Prima Facie limit is an upper bound.

The Maximum Speed Requirement means that no matter how high the Prima Facie limit may allow you to drive, you must never drive too fast for current conditions (maybe rain, traffic, snow, etc.).

So, Prima Facie simply is the upper bound of "reasonable and prudent". Maximum Speed means that given certain conditions, actual "reasonable and prudent" could be far below the Prima Facie limit. It's not the other way around which is what I am getting from your message.

Whether the Prima Facie limit on a particular road is realistically the upper bound of "reasonable and prudent" is a whole different debate (and I would generally agree that those limits are often absurdly low).


Regarding the gearing: According to that nice chart posted above, the Z51 gearing looks quite good based on what first gear gives. Each shift takes you from redline to about 4500 RPM (up to 5th gear). Looking at some of the dyno charts (still don't think I've seen one go to redline yet) it seems like the LT-1 is making about 400 HP @ 4500 RPM and will likely be dropping to about 400 (or slightly over) at redline. So the gears are nicely bracketing the power peak of the engine. Seems pretty good to me. It does almost look like the should have kept the same 6th and 7th as the base car though.

-T

SCM_Crash

7th gear is not [strictly] marketing. It's purposeful. If GM was strictly doing it for marketing, they would have made the gear ratios closer so they could brag about "closer ratios" as well as a 7th gear. But what they did was put a 3rd overdrive in to increase economy. It's really that simple. I don't get why SOME people continue to insist it was marketing.

In reality, the entire CAR is marketing. There's nothing practical about the Corvette. Sure it's daily driveable with good trunk space and good economy... Doesn't make it practical... especially for the price. But it does serve as GM's "look what I can do" demonstration.

In any case, you can (in theory) call anything on the Corvette "marketing". But that doesn't mean whatever it is came without function.

Get your heads out of your asses, please.

theseal

Prima facie means 'on the face of it'. It is not conclusive or irrebuttable. It just means the commies charging you dont have to put on expert testimony to prove your speed is unreasonable if its over the posted speed. If you put on evidence that 100 is reasoanable the jury is just as entitled to believe you as they are the stalinists.

1analguy

Lighten up, Francis...

Trackaholic

My understanding is that in a legal sense it essentially means that the point is already taken as fact. You would need to provide the burden of proof otherwise. Your quote above seems to indicate the same understanding, so I guess in a sense we agree. I'm not sure sure of the jury situation as I've always caved to the commies and simply paid my "speed tax".

There are definitely some areas I have in mind where I think a good argument could be made about the posted limits being unreasonably slow (and where the sheriffs like to trap people). If I ever get ticketed there I'll have to keep your premise in mind.

-T

4GS7

I love when people with no legal training try to interpret the law.

545.351 refers to reasonable and prudent given the conditions. .352 states that exceeding the posted speed limit is prima facie evidence that your speed violates 545.351. However, to rebut that statutory presumption, you'd have to show exigent circumstances, not that your speed was simply reasonable because you think it was. The policy interest in maintaining lower speed limits to reduce the level of injury in accidents will ALWAYS trump if you actually ever tried to go toe to toe with the state on the reasonableness of the posted speed limit.

johnglenntwo

Then watch the new casting go to work!

cqz

I don't know about you guys, but I'm incredibly grateful for that seventh gear. It'll make cruising at 85 so much more economical.

1analguy

Rather than messing around with a different transmission ratio set for the Z51, I'm a little surprised that they didn't just shorten up the final drive ratio instead...to something in the 3.90-or-so range. It probably wouldn't even have hurt the mileage all that much, as it would have allowed the car to remain in 4-cylinder mode even longer. The way they went about it, 1st gear will be almost useless for anything other than drag launches...

SCM_Crash

I believe the lower ratio was actually saving more fuel than 4-cyl mode.

BLKTA

Here is a good article on the TR6070 with pics.

http://www.gmhightechperformance.com..._transmission/

rgamache

At LimeRock last weekend, Harlan Charles, Corvette Product Marketing manager, attempted to answer that question. His pitch was that with the very wide torque band of the new engine, close ratio is not necessary, and the 0.5 7th helps avoid the gas guzzler tax. With the engine in Eco mode plus 7th ratio...30mpg on highway.