LB001

I realize this subject is discussed in technical detail in the Tech/Performance section of this forum. I'm looking for an answer in layman's terms. The 2015 Stingray comes with a rear axle ratio of 3.42. An optional performance rear axle ratio of 2.73 is offered. My question is why wouldn't the "performance" ratio be standard in the Z51 package? (Or is it?) Is there a downside to the performance ratio, such as less gas mileage, or lower top speed?

green2000

3.42 is the 7-speed ratio. 2.73 is the performance ratio for the automatic. I think the standard auto ratio is 2.56.

St!ngray

An answered to my question similar to yours.
It was posted by ZL1.

The MEL is the Z51 trans with wider 1 through 4 ratios starting with a 2.97:1 first gear

The MEP is the base trans with closer 1 through 4 ratios starting with a 2.66:1 first gear

All have a 3.42:1 axle ratio

All are 1 to 1 in 4th gear

In the overdrive 5th, 6th, and 7th gears the Z51 MEL ratios become closer while the base MEP ratios become wider, with a 0.42 7th gear.

RicK T

The A6 has a first gear ratio of 4.03.....that works with the standard 2.56 or Z51 performance 2.73 axle ratios.

If you noticed, the 2015 A8 has a 2.41 axle. The order guide highlights say the 2.56 is deleted. So one might assume the 2.73 will still be offered as the performance ratio with the A8, which has a 4.56 first gear.

Corgidog1

2.41 rear axle ratio for A8 replacing 2.56 for the A6. Well without knowing anything else, the score is 1 to 0 in favor of the A6.

fdxpilot

The total gear ratio (tranny x rear) for the A6 is 10.32. For the A8, it is 10.99, so the A8 has more gear than the A6 in first gear. Both are better than the Z51 M7.

When you select the Z51 package, which comes with the 2.73 rear end, the total ratio is 12.45.

green2000

The standard axle in automatic Z51 is 2.73.

BRCC

Overall Ratio A6Z A8 A8Z

First gear...............11.00..10.99 ..12.45
Second gear............ 6.44.. 7.16 .. 8.11
Third gear............... 4.18.. 5.01 .. 5.68

mkr1966

Better than the Z51 M7? Uh... no.

eboggs_jkvl

Transmission and rear gearing Z51, Non Z51 - 2005-2015

JerryU

This is another way to look at the numbers:

A8 Z51: First Gear = 4.56:1 / Rear = 2.73:1 / Combined = 12.5:1


M7 Z51: First Gear = 2.97:1 / Rear = 3.42:1 / Combined = 10.2:1

In addition, the A8 (and all automatics) have significant torque multiplication from the torque converter at launch. This could double the initial torque however with some efficiency loss compared to gears.

thrilled

I think the 1st gear is to low in my M7.So would there be any problems in changing the rear
To maybe the rear for the Z51 6 speed ,or even the 8 speed auto?

eboggs_jkvl

You are thinking of going from a 3.42 to a 2.73 or a 2.41? Why would you want less acceleration capability? The 3.42 (with the same tranny gearing) is quicker than the other two. You might consider a 3.73 rear for quicker acceleration but not a lower gear ratio.

If you would give up acceleration, then those other two gear ratios (2.73 or 2.41) would give you better gas mileage at highway speeds. Probably would lower your gas mileage in the city as those ratios are for cruising, not starting.



Elmer

fdxpilot

We are talking gear ratios here. 3.42 x 2.97 = 10.16, so compared to the '14 non Z A6 at 10.32 or the '15 non Z at 10.99, uh... Yes.

robertf97

Wheelspin. Especially after you put a power adder on.

WelderGuy

Keep in mind that the tires are different between the base and the Z51 models, and that changes the effect of the difference in axle ratios a little. You can get the revs-per-mile info in Tire Rack specs.

Zymurgy

Gear Ratios:

...........................A6....Z51A6.. ...A8....Z51A8....MN7...Z51MN7
.........................------..------..------..------..------..------
First gear............... 4.03 .. 4.03 .. 4.56 .. 4.56 .. 2.66 .. 2.97
Second gear.............. 2.36 .. 2.36 .. 2.97 .. 2.97 .. 1.78 .. 2.07
Third gear............... 1.53 .. 1.53 .. 1.30 .. 2.08 .. 2.08 .. 1.43
Fourth gear.............. 1.15 .. 1.15 .. 1.00 .. 1.69 .. 1.69 .. 1.00
Fifth gear............... 0.85 .. 0.85 .. 0.74 .. 1.27 .. 1.27 .. 0.71
Sixth gear............... 0.67 .. 0.67 .. 1.00 .. 1.00 .. 0.50 .. 0.57
Seventh gear............................. 0.85 .. 0.85 .. 0.42 .. 0.48
Eighth gear.............................. 0.65 .. 0.65 .. .... .. ....
Reverse...................3.06 .. 3.06 .. 3.82 .. 3.82 .. 2.90 .. 2.90

Axle ratio............... 2.56 .. 2.73 .. 2.41 .. 2.73 .. 3.42 .. 3.42

Overall ratios:
...........................A6....Z51A6.. ...A8....Z51A8....MN7...Z51MN7
.........................------..------..------..------..------..------
First gear...............10.32 ..11.00 ..10.99 ..12.45 .. 9.10 ..10.16
Second gear.............. 6.04 .. 6.44 .. 7.16 .. 8.11 .. 6.09 .. 7.08
Third gear............... 3.92 .. 4.18 .. 5.01 .. 5.68 .. 4.45 .. 4.89
Fourth gear.............. 2.94 .. 3.14 .. 4.07 .. 4.61 .. 3.42 .. 3.42
Fifth gear............... 2.18 .. 2.32 .. 3.06 .. 3.47 .. 2.53 .. 2.43
Sixth gear............... 1.72 .. 1.83 .. 2.41 .. 2.73 .. 1.71 .. 1.95
Seventh gear............................. 2.05 .. 2.32 .. 1.44 .. 1.64
Eighth gear.............................. 1.57 .. 1.77 .. .... .. ....

eboggs_jkvl

No post in this thread mentioned a FI or power adder. I am answering using what the Stingray came from the factory with and not the Z06.

FI? Well, maybe keep the ratio and getting bigger sticky drag radials or something. Sounds like a topic for a new thread.

Elmer

green2000

It seems to me that you might be better off just by starting in 2nd gear. At least you could try it for a while at no cost.

JoesC5

The difference in the tire circumference is so small between the base C7 and the Z51, it has practically no impact on the cars gearing. Less than one half of one percent.