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Discussion Starter #1
Since at this point most of us prospective owners are essentially after a new Z06 that is "built to order", does anyone know if it is or would be "possible" to order with the 3.15 axle ratio? A 3.15 axle ratio is an option on automatic transmission equipped Coupes and Convertibles, so why not on the Z06?

I think it would be a desireable "option" for those of us that do not intend to put our cars on the track.

As an aside, the one thing holding these cars back as far as it's credential to become the new KOTH Corvette, is it's top speed rating. A speed in the low 170s is several MPH less than all model year C5 Coupes and certainly less than the now defunct ZR-1 Corvette. It would be great if the Z06 became the new KOTH and dethrone the ZR-1 for that honor in all possible categories.

As much as having ultimate bragging rights would mean to most Z06 owners, I would just as soon have a car that gets even better gas mileage on the highway. To me a phenomenal performance car that gets nearly 30mpg is also a form of bragging right. /phpBB/images/smiles/icon_wink.gif

All Corvettes come with "Y" speed rated tires, so improving the Z06's top speed should be in keeping with it's image as the new KOTH. But, since there is a tradeoff in other areas of performance, it would be best if the 3.15 axle ratio were treated as an option only just like it is on the automatics.
 

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You would probably see less than 10 mph top speed, you would give up some of the 0-60 times, I would rather go the other way and have 3.73's in the car, but the 3.42's will be fine for what I am looking for. I am sure you could pick up 3.15's pretty cheap from someone who went with a taller gear.
 

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Discussion Starter #3
I will do a "what if" prediction for the Z06 (stock) with a 3.15 axle ratio tonight and see what it's theoretical top speed might be if so equipped.

Since a stock ZR-1 with 0.34 Cd was capable of 180mph with only 375HP at the crank, I'd be very surprised if a 405HP Z06 with a 0.31 Cd isn't as fast or even faster with a lower numeric axle ratio. I believe 185mph might even be possible, which would rival a Dodge Viper GTS Coupe. /phpBB/images/smiles/icon_wink.gif

I use PC Windows based, software application called "CAR TEST" (developed by Dana Gehm, a rocket scientist . . . literally) to make such top speed determinations. It's a great program and I highly recommend it.
 
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I have been doing open road racing for some years so topend speed has been part of what we try to master.

The following is results using my Mallett 450 and should be noted it is a non Z06 MN6, thus results would be slightly different with a Z06 MN6 due to its different gear ratios in trannie.
Tires are 30 series and fronts are also 18 inch. Reults are time and distance to get to maximum topend speed using a certain rear gear.

Rear Gear Topend Time Distance

3.15 193MPH 135Sec 33,840 feet
3.42 189 102 25,000
3.73 181 79.86 17,931
4.11 188 181 45,688

So if you compare the stock gear V the 3.15, it has a bit higher topend but takes just about another 2 miles to get to that speed.

It's interesting how the 3.73 gets the job done in half the time and distance then a 4.11 would.

Problem is with a 3.73 ( which is what I am running now) is it sucks for drag racing since toque/HP of this car are not a good marriage with that gear for the tires are being way overpowered and causes a 4th gear shift that adds time to E.T.

I've been to 185 MPH and frankly if that is your path then other then gear is the car needs aerodynamics mods.
 

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Just want to help clarify... I love my Z-06, and like the idea of being able to 'pick and choose' ratios, and options! That would be great!

BUT... just to help the Viper story... Viper's are in excess of 190+ STOCK! So... I don't think we are quite there! Depending on what year, and Mag you read... the fastest tested I believe is 196! /phpBB/images/smiles/icon_eek.gif

Peace,
Dave
 

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dsinned, I must admit: that is a rather unusual wish! /phpBB/images/smiles/icon_smile.gif Most people (I included) crave for mind bending acceleration and in this respect, you could not make the gears short enough (numerically higher) for me. I test the acceleration of my car every half chance I get, and while top speed is certainly a benchmark for high performance cars, it is one aspect that most drivers will never safely (or legally) explore. That said, with the 3.15 rear, the Z will definitely hit 180 mph and likely flirt with 185 mph at redline in 5th. But the right solution would be a usable 6th gear ratio of ~0.74:1 (leaving other ratios including the rear as is) that would not sacrifice acceleration, yet will get you into that elusive 180+ mph space for bragging rights! /phpBB/images/smiles/icon_smile.gif
 

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I like that idea, make 6'th gear usable.

Mike
 

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Discussion Starter #8
You missed my point. Top speed bragging rights AND 30 mpg highway . . . best of both worlds.

Furthermore, it is "acceleration" & the pursuit of it, for its own sake, that is more likely to be UNSAFE and get one killed.

On this point, I speak from experience. ;-(

Running at top speed, under relatively safe and/or controlled conditions, such as in open road racing, is in fact very "doable" for ANY ordinary driver of virtually ANY type of car, especially Corvettes, and is certainly LEGAL.

Go to http://www.openroadracing.com and check it out. But don't be mislead by the name of the organizing body. Their events cater mostly to late model Corvettes by far.

I just got back from the last ORRing event, my 12th, and drove my LT4 as fast as it will go and even got it clocked on radar without getting a ticket. 170.6 mph, not too shabby for a stock LT4 (for sale by the way), and just as fast as a Z06, with only mid 90's Corvette performance enhancements technology.

BTW, I just checked the 2002's theoretical top speed potential with my "what if" predictor program. Guess what? With a 3.15 rear, the car, otherwise stock, would most likely go (censored). /phpBB/images/smiles/icon_wink.gif
 

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Hi there,
I think that the real reason why you do not see something like that is EPA.
There are 3 reasons that anything happens with Corvette, or any car for that matter. Someone has a bright idea, manufacturing costs, or law. GM has to bring every powertrain through EPA legalities to produce a vehicle.
If you remember back in 96, the reason we didnt see an LT1, six speed was the extra cost and expense of having another EPA certification.
So, I feel that this could be the reason for no gearing option in ZO6.
Best to you, c4c5
 

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Discussion Starter #10
C4C5, since you're a late model Corvette mechanic, I would value your expert knowledge and/or opinion. Can you tell us the compatibility of the 3.15 gears (out of the Automatic C5's drivetrain) with the Z06 rear end?
 

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The Doctor (C4C5) is right on! One of the reasons that an auto tranny/different exhausts and other options we might want are not offered was the certification process (according to one of the guys in the Corvette group I chatted with at Carlisle last year). For a run of 5K cars. the EPA certification was not justified...every time they make a change that could affect EPA they have to run it through the tests. All of that costs bucks...
 

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Hi there again,
Well, physically, it will bolt right in. However, I would have an issue with the program of the PCM, and the EBTCM.
These will be issues, as the Active handling, and the throttle control may not operate correctly.
Personally, I would not attempt this, unless I am ABSOLUTELY positive that the calibration will work correctly.
Besttoall, c4c5
 
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