FRANKENSTEIN4x42000

Hi I just bought a used C6 with the Z51 option I have own 2 C6 before without and my rpm was about 1200/1300 at 60mph this one is about 1800 I realize the gearing is a bit different but that much difference? what's your running at?
thanks

PDsVettes

I have a 2008 Z51 A6 with 2.73 axle ratio. I think the MN6 has a 3.42 axle ratio. With my A6, at 75mph my RPM is around 1700.

FRANKENSTEIN4x42000

sorry I forgot to mention mine is a 6 speed manual

extrapilot

My 2006 Z51 MN6 will cruse at 80mph with the engine rpm right at 2000.
It's not the rear gear that makes it a lower ratio, it's the sixth gear in the transmission of the Z51 manuals.

FRANKENSTEIN4x42000

thanks, it's amazing how much of a difference there is from .50 to .57

cmonkey713

My 2007 Z-51 has a 2:54 gear.

PDsVettes

Frankenstein,
You should put your specs into a gear/mph program and see what you come up with. What is your tire size? That also can make a difference if you have gone away from a stock size.

MTsVette

Ditto

I have a '12 GS A6 w\2.73's. 1,600 rpm at 70 mph.

MT

dshamrick

Mine is Z51 and MN6 and I can cruise all day long at 75mph @1800 rpm and 26 mpg

PDsVettes

Why the 15 mph difference at 1800 RPM. Tire circumference?

RobLo

'05 A4 Z51, 3.15 gears...

hisvett

Transmissions Gearing; Base and Z06 Vs. Z51 Vs. 6-speed paddle-shift automatic
Application: std Z51 A6

First: 2.66 2.97 4.03
Second: 1.78 2.07 2.36
Third: 1.30 1.43 1.53
Fourth: 1.00 1.00 1.15
Fifth: 0.74 0.71 0.85
Sixth: 0.50 0.57 0.67
Reverse: 2.90 3.28 3.06
Final drive ratio: 3.42 3.42 2.56

Sorry about all the tabs not transferring correctly but you get the idea; Z51 (and GS) manual trans has lower gearing than Base/Z06 by .07 in top gear..... or about 200 revs. If your seeing more than that, you might want to check your rear end gears.....someone down the line may have gone for lower drag gears.

ls1121

Interesting information.

A 2004 Chevrolet Corvette C5 Z06 with a six-speed manual transmission has the following gear ratios in the transmission:
Gear Ratio
1st gear 2.97:1
2nd gear 2.07:1
3rd gear 1.43:1
4th gear 1.00:1
5th gear 0.84:1
6th gear 0.56:1
reverse -3.38:1

In 1st gear, the engine makes 2.97 revolutions for every revolution of the transmission’s output. In 4th gear, the gear ratio of 1:1 means that the engine and the transmission's output rotate at the same speed. 5th and 6th gears are known as overdrive gears, in which the output of the transmission is revolving faster than the engine's output.

The Corvette above has an axle ratio of 3.42:1, meaning that for every 3.42 revolutions of the transmission’s output, the wheels make one revolution. The differential ratio multiplies with the transmission ratio, so in 1st gear, the engine makes 10.16 revolutions for every revolution of the wheels.

The car’s tires can almost be thought of as a third type of gearing. This car is equipped with 295/35-18 tires, which have a circumference of 82.1 inches. This means that for every complete revolution of the wheel, the car travels 82.1 inches (209 cm). If the Corvette had larger tires, it would travel farther with each revolution of the wheel, which would be like a higher gear. If the car had smaller tires, it would be like a lower gear.

With the gear ratios of the transmission and differential, and the size of the tires, it becomes possible to calculate the speed of the car for a particular gear at a particular engine RPM.

For example, it is possible to determine the distance the car will travel for one revolution of the engine by dividing the circumference of the tire by the combined gear ratio of the transmission and differential.

d = \frac{c_t}{gr_t \times gr_d}

It is also possible to determine a car's speed from the engine speed by multiplying the circumference of the tire by the engine speed and dividing by the combined gear ratio.

v_c = \frac{c_t \times v_e}{gr_t \times gr_d}
Gear Distance per engine revolution Speed per 1000 RPM
1st gear 8.1 in (210 mm) 7.7 mph (12.4 km/h)
2nd gear 11.6 in (290 mm) 11.0 mph (17.7 km/h)
3rd gear 16.8 in (430 mm) 15.9 mph (25.6 km/h)
4th gear 24.0 in (610 mm) 22.7 mph (36.5 km/h)
5th gear 28.6 in (730 mm) 27.1 mph (43.6 km/h)
6th gear 42.9 in (1,090 mm) 40.6 mph (65.3 km/h)

PDsVettes

You need to make a note in your data that if your car with an A6 has the Z51 package, the final drive ratio is 2:73, at least for a 2008.

RicardoFors68

All A6 Z51 cars came with 2.73?

PDsVettes

I don't know about that. GM seems to change things quite often. My window sticker for my 2008 Z51 shows that a performance axle is listed under the Z51 Performance Pkg option. The RPO sticker on my glovebox lid has GU2, which is the 2:73 rear axle ratio. So I am assuming that all 2008 Z51's have a 2:73 rear gear. Not going out on a limb for any other year.