KWC6

Ok I get some of it. The Z51 has the 2.73 and base non has 2.42. That is really close so I wonder how much of a difference does it really mean. For the average non racer, can we really feel the difference? Maybe a slight edge in the 1/4 mile. Reminds me of the C6 A6. The Z51 had 2.73 and base had 2.56. Is it worth it for GM to make 2 different gears?

Zymurgy

Gear Ratios (M7, A8):

...........................A8....Z51A8.. ...MN7...Z51MN7
.........................------..------..------..------
First gear............... 4.56 .. 4.56 .. 2.66 .. 2.97
Second gear.............. 2.97 .. 2.97 .. 1.78 .. 2.07
Third gear............... 2.08 .. 2.08 .. 1.30 .. 1.43
Fourth gear.............. 1.69 .. 1.69 .. 1.00 .. 1.00
Fifth gear............... 1.27 .. 1.27 .. 0.74 .. 0.71
Sixth gear............... 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.................. 3.82 .. 3.82 .. 2.90 .. 2.90
Axle ratio............... 2.41 .. 2.73 .. 3.42 .. 3.42

Overall ratios:
...........................A8....Z51A8.. ...MN7...Z51MN7
.........................------..------..------..------
First gear...............10.99 ..12.45 .. 9.10 ..10.16
Second gear.............. 7.16 .. 8.11 .. 6.09 .. 7.08
Third gear............... 5.01 .. 5.68 .. 4.45 .. 4.89
Fourth gear.............. 4.07 .. 4.61 .. 3.42 .. 3.42
Fifth gear............... 3.06 .. 3.47 .. 2.53 .. 2.43
Sixth gear............... 2.41 .. 2.73 .. 1.71 .. 1.95
Seventh gear............. 2.05 .. 2.32 .. 1.44 .. 1.64
Eighth gear.............. 1.57 .. 1.77 .. .... .. ....


While numerically, it doesn't seem like much, it is an over 13% difference.

Always Red Dave

base has 2.56 gears I believe so.

Zymurgy

There are no 2.56 gears:

GU6 Rear axle, 3.42 ratio, limited slip (manual trans base and Z51)
GXB Rear axle, 2.41 ratio, limited slip (auto base only)
GU2 Rear axle, 2.73 ratio, electronic limited-slip, performance (auto Z51 only)

Ignoring Z06 for this discussion.

sTz

Yes... and the overall tire circumference is slightly different. The taller gears help to compensate the difference...

meyerweb

The eLSD is only available with the automatic?

BJ67

Like a 3.42 v/s a 3.73 gear, a noticeable seat of the pants difference.

Zymurgy

No. eLSD is on all Z51's.

Z51 Performance Package, includes (J55) performance brakes, (J6A) Black-painted calipers, slotted brake rotors, (Z52) dry sump oil system, (FE3) Z51 performance suspension, specific shocks, springs and stabilizer bars, (NPP) performance exhaust, (XFJ) P245/35ZR19 front and P285/30ZR20 rear tires, (Q7S) Silver-painted aluminum, 19" front and 20" rear wheels, performance gear ratios, (G96) Electronic Limited Slip Differential (eLSD), (KNR) rear differential cooler, transmission cooling and an Aero Package

G96 Differential, electronic limited slip, rear

lakemg

In the Pontiac G8 world, swapping out the GT's standard differential (2.92) for that of the standard A6 GXP (3.27) would get you roughly a 0.1 to 0.2 sec improvement in the quarter mile, so I suspect the C7 would see a similar improvement going from the 2.41 to the 2.73. If I'm not mistaking, the Z51 is a tad heavier so the difference might not be as noticeable.

DAFFYDRUNK

Once hind sight is truly 20/20, I'll guess the A8 base and Z51 will end up being a statistical wash for straight line accelleration. For the Z51, steeper gears are offset by heavier weight and and what I think would be an extra shift in the 1/4 for a bone stock C7. 4th to 5th at ~113ish compared to ~123ish mph? LT1 has a pretty wide torque curve so there's less reason to "keep it in the powerband". Either config is traction limited so no real difference on the short end either.

T-Z06-J

i agree with his question. If one is better than the other then just make the better one and sell all corvettes with it.
I don't know much about automobile production but from my internet forum education, it is cheaper for the manufacturer to just produce one part.

RPOC7R

According to the 2016 Corvette brochure:

- The Base Stingray A8 has a 2.41 axle ratio and a 0 to 60 MPH time of 4.0 seconds. No quarter mile performance is reported.

- The Z51 Stingray A8 has a 2.73 axle ratio, a 0 to 60 MPH time of 3.7 seconds and quarter mile performance of 11.9 seconds at 119 MPH.

Based on my many years of drag racing experience, the 3/10's of a second ET difference in 0 to 60 MPH performance would carry through to the quarter mile finish line, yielding a quarter mile ET of 12.2 seconds for a Base Stingray. Each 1/10 of a second in quarter mile ET yields a one car length difference at the quarter mile finish line. Hence assuming identical reaction times and hook on starting line launch, a Z51 Stingray would cross the quarter mile finish line three car lengths ahead of a Base Stingray. My estimate is that the performance differential between a Base Stingray with the performance exhaust option and a Z51 Stingray would be between 2/10's and 3/10's of a second in 0 to 60 MPH and quarter mile performance.

Bucknut2006

Is the Z51 A8 rear end just as strong as the Z51 M7? Wonder if it would be possible to swap the two.

BJ67

Its because Chevrolet is giving us a choice, one is better for performance, the other is better for MPG. Choice and variability is a good thing, not one fits all mentality.

BJ67

A base A8 is close to 100 lbs lighter than a Z51 A8. IMO, the gear difference between these 2 examples would be hard pressed to have a .2 difference in 1/4 mile et.

meyerweb

That's what I thought, but your earlier post has the comment (auto Z51 only) next to the eLSD:

meyerweb

FWIW, CarCraft magazine thinks the lighter weight of the base model is worth more in the quarter than the gearing and wider tires of the Z51:

http://www.carsillustrated.com/secre...d-c7-corvette/

BJ67

That means the 2.73 ratio elsd is for the A8 Z51 cars only.

BJ67

It would at least make the cars very close. I would always favor less weight over a more aggressive gear ratio.

C2367

Base NPP, A8 no mods with DR's 1100' elevation