Sub optimal gear ratios and final drive

[Gottagofast]

Hello everyone.

I've been researching some of the mechanical aspects of the C8 Z06 and In my opinion, the gearbox leave quite a bit to be desired. I know that most people do not care or won't have a problem with the Z06 as it is a wonderful car to drive. I have also put a deposit down just yesterday to get one hopefully before the end of this year, all thanks to @Mr.Corvette (Scott). But I still have to point this out as a bit of a let down.

Before I state my opinion, I will say that perhaps the reason the gearbox is the way it is, might be down to a lot of things that may or may not be directly related to performance. Things such as desired fuel economy, mechanical stress and durability, emission targets, weight targets, packaging constraints, cost, etc. Nevertheless, the end result in this case and in my opinion only, is either reduced performance or a diminished driving experience.

To cut it short (Hehe), I think the Z06 gears are way too long. With the Z07 high downforce package, your top speed is limited to around 188 mph which is more than adequate, but you reach that speed in 5th gear! In a car with a gearbox that has 8 gears!

Having a tall final drive ratio or top gear or both, will result in reduced RPM at highway cruising speeds which makes the car quieter and increases fuel economy, both great things. However, in a car with 8 gears, this is less of a problem versus let's say, a manual 6 speed transmission.

For example, The ZF 8HP gearbox in a BMW G82 M4 CS that I'm also getting, hit's the same exact top speed but it does so in 7th gear. It's not a DCT, it's a torque convertor unit but the shifts are very fast and very smooth. The gear ratios are much shorter even though the torque output of the S58 engine dominates the LT6 across the RPM range, achieving its maximum torque of 480 lb.ft at 2650 RPM and carrying it to 6000 RPM. The gears are so short that you need to be in third gear to hit 60 mph. That might sound a bit absurd for a car with so much power, but the sensation of going through the gears so quickly, without going so fast as to become a public nuisance and a safety hazard, is immaculate. I think they should have done something similar with the Z06 or even the base corvette.

The 8th gear is so long in the Z06 (0.33:1 ratio) that you'll be ticking at just 1600 RPM when going 70 mph. Very little torque is available at those engine speeds, around 150 lb.ft or less, definitely not suitable for highway driving if you need to overtake someone without having to shift down a few times while driving in manual mode. Even the 7th gear is exceptionally long. At 0.40:1 ratio, you'd be around 1900 RPM doing 70 mph. See the problem here?

I don't know why GM chose these ratios. I really hope, perhaps in the future, they give you an option of shortening the final drive or ring and pinion ratio to make this great car, even better. Seems like a big missed opportunity.

 

[Murray20c8]

I have no idea as I've never even driven a car that can rev to 8000 rpm.

 

[E-TownC8]

Where do you start on this discussion... C8 Z06 and M4 are 2 different animals. The Z06 is a no-holds barred track car, with engine, transmission gears the entire power train designed to maximize drag strip and racetrack performance - 0-60 mph, 0-100 mph, you name it. A lower final drive would also mean the first few gears would be too low and would provide sub-optimal launches. Yeah, the top couple gears are meant for street use to reduce fuel consumption, noise etc. but the reality is very few Z06's (or M4's) will be tracked anywhere near the car's full capability. The turbo M4 has a much bigger power band so you can do things differently. The Z07 package is all about maximum cornering grip and sacrifices top speed to do it. If you're going to run the car on the Bonneville salt flats, and don't want to pull a parachute behind you, don't buy the Z07 package - and top speed will probably happen in 6th gear.

 

[DenisC8]

OP, you are wrong because you are doing hypothetical napkin math as you don't own/drive either of the cars you mentioned. I own a B58 engine/ZF 8 speed BMW and two C8s (non-z51 and z51 which have different rear end ratios). C8 DCT gear ratios and rear end ratios are perfect, short enough, and would have been taller if GM engineers didn't design the C8 with TQ by gear that limits TQ in 1st and 2nd gear which your napkin math does not account for. This combination of ratios is the reason by C8s are doing 0-60mph in 2.8 sec and any shorter gear ratios will lead to slower acceleration due to loss of traction.

you will see/feel exactly what I mean when you drive your future BMW and C8

 

[Gottagofast]

Where do you start on this discussion... C8 Z06 and M4 are 2 different animals. The Z06 is a no-holds barred track car, with engine, transmission gears the entire power train designed to maximize drag strip and racetrack performance - 0-60 mph, 0-100 mph, you name it. A lower final drive would also mean the first few gears would be too low and would provide sub-optimal launches. Yeah, the top couple gears are meant for street use to reduce fuel consumption, noise etc. but the reality is very few Z06's (or M4's) will be tracked anywhere near the car's full capability. The turbo M4 has a much bigger power band so you can do things differently. The Z07 package is all about maximum cornering grip and sacrifices top speed to do it. If you're going to run the car on the Bonneville salt flats, and don't want to pull a parachute behind you, don't buy the Z07 package - and top speed will probably happen in 6th gear.

I daily a '23 M4 XD, the engine and transmission are identical to the CS. CS has higher boost for more power and the transmission programming has been changed to decrease shift times further. Gear ratios are also identical. I can only imagine how much more exciting the CS is going to be.

I don't care about the top speed of most sports cars as they're just a number on a sheet so you can play trump cards. The Z07 package reduces the top speed of the "base" Z06 from 195 mph to 188. It makes no difference to me that it's down 7 mph. I also don't care about 0 to 60 times, quarter mile times or any stats related to pressing a button, putting your foot on the accelerator and holding the wheel straight while the car goes fast in a straight line. Sure, the acceleration of my M4 is brutal and it's fun to do it once in a while but it's not as engaging as driving on a curvy b road and constantly going up and down the gears (mostly second and third) because of the super short gears. You don't need to go very fast to have fun in a car with short gearing. If BMW chose a longer 1st and 2nd gear for the M4 so that you didn't have to shift to 3rd gear to reach 60 mph, you would have a sub 3 second 0 to 60 car, but they didn't, and for a good reason too. They put driving experience above some spec sheet numbers.

Even McLaren dropped the final drive ratio of 750S by 15% compared to the 720S. That reduced the top speed by a good chunk and didn't improve the acceleration, 0 to 60, or quarter mile at all, but nobody cared because it made the car more exciting to drive by increasing driver interaction.

I also enjoy track driving and have the production car track record at TMP (Hostile), so I know what I'm able to do behind the wheels:

Toronto Motorsports Park lap times - FastestLaps.com

List of fastest lap times for Toronto Motorsports Park. Updated September 2024.

fastestlaps.com

You don't ever use launch control on a race track unless you're drag racing so optimizing the gear box to manage 2.8 seconds to 60 is just not relevant. If the car is so focused for track use and everything is so optimized, why have a 7th or an 8th gear? Two unwanted gears that just adds extra mass. You might use 6th gear for highway cruising but if you hit your top speed in 5th, then why does that matter? Perhaps having a 8 speed DCT on the spec sheet is more sellable than a mere 6 speed box.

GM doesn't even have to shorten the final drive. They can leave 1st and 2nd the way they are and just shorten the rest of the gears. Give me a reason to use those last few gears or get rid of that dead weight.

OP, you are wrong because you are doing hypothetical napkin math as you don't own/drive either of the cars you mentioned. I own a B58 engine/ZF 8 speed BMW and two C8s (non-z51 and z51 which have different rear end ratios). C8 DCT gear ratios and rear end ratios are perfect, short enough, and would have been taller if GM engineers didn't design the C8 with TQ by gear that limits TQ in 1st and 2nd gear which your napkin math does not account for. This combination of ratios is the reason by C8s are doing 0-60mph in 2.8 sec and any shorter gear ratios will lead to slower acceleration due to loss of traction.

you will see/feel exactly what I mean when you drive your future BMW and C8

I daily a '23 M4 XD, it's very fast. S58 is a supped up version of B58 so it's as good as straight 6 is gonna get for the moment.

The gear ratios are by no means perfect. I suppose they are good enough for 0 to 60, but the primary reason the vette can't do faster than 2.8, regardless of trim or power, is traction. This guy has a fantastic explainer for why the theoretical 0 to 60 time of a C8 is 2.76 seconds, whether it's the base C8, Z06, or ZR1.



On another note, the 1st gear is, for the most part, unusable on a race track. You don't do any hard launches or start from a stand still on a proper track so you never go down to first. Most of the time, you don't even need to use 2nd as traction can be a problem on slow speed corners, specially on exit.

 

[Mr.Corvette]

Your on the right track here, but lets put a pin in this discussion until after you drive the Z06 with the Z07 on the track. You will not use first gear except coming onto the track, you will use 2nd through 5th. The final two gears are both overdrive gears for fuel economy and reduced noise. In the US the car even with the overdrive gears gets a 3K gas guzzler penalty. During testing they run the cars at 1600 rpm at highway speeds which helps them pass the noise requirements. There is no cylinder deactivation in the Z06 which hurts the EPA fuel economy ratings. I think you will be pleased with how the car runs on the track in 2nd through 5th gears. The majority of people that buy the Z07 cars never track them and the gearing is set up for the average buyer. Your right though a shorter 2nd through 5th for track use would have been preferred so the only thing you can do is adjust the settings in track mode to what features you want on and off to go along with the more aggressive shifting to meet your preferences. I think while not ideal, you will be very impressed with the car.

 

[Gottagofast]

Your on the right track here, but lets put a pin in this discussion until after you drive the Z06 with the Z07 on the track. You will not use first gear except coming onto the track, you will use 2nd through 5th. The final two gears are both overdrive gears for fuel economy and reduced noise. In the US the car even with the overdrive gears gets a 3K gas guzzler penalty. During testing they run the cars at 1600 rpm at highway speeds which helps them pass the noise requirements. There is no cylinder deactivation in the Z06 which hurts the EPA fuel economy ratings. I think you will be pleased with how the car runs on the track in 2nd through 5th gears. The majority of people that buy the Z07 cars never track them and the gearing is set up for the average buyer. Your right though a shorter 2nd through 5th for track use would have been preferred so the only thing you can do is adjust the settings in track mode to what features you want on and off to go along with the more aggressive shifting to meet your preferences. I think while not ideal, you will be very impressed with the car.

 

[DenisC8]

I daily a '23 M4 XD, the engine and transmission are identical to the CS. CS has higher boost for more power and the transmission programming has been changed to decrease shift times further. Gear ratios are also identical. I can only imagine how much more exciting the CS is going to be.

I don't care about the top speed of most sports cars as they're just a number on a sheet so you can play trump cards. The Z07 package reduces the top speed of the "base" Z06 from 195 mph to 188. It makes no difference to me that it's down 7 mph. I also don't care about 0 to 60 times, quarter mile times or any stats related to pressing a button, putting your foot on the accelerator and holding the wheel straight while the car goes fast in a straight line. Sure, the acceleration of my M4 is brutal and it's fun to do it once in a while but it's not as engaging as driving on a curvy b road and constantly going up and down the gears (mostly second and third) because of the super short gears. You don't need to go very fast to have fun in a car with short gearing. If BMW chose a longer 1st and 2nd gear for the M4 so that you didn't have to shift to 3rd gear to reach 60 mph, you would have a sub 3 second 0 to 60 car, but they didn't, and for a good reason too. They put driving experience above some spec sheet numbers.

Even McLaren dropped the final drive ratio of 750S by 15% compared to the 720S. That reduced the top speed by a good chunk and didn't improve the acceleration, 0 to 60, or quarter mile at all, but nobody cared because it made the car more exciting to drive by increasing driver interaction.

I also enjoy track driving and have the production car track record at TMP (Hostile), so I know what I'm able to do behind the wheels:

Toronto Motorsports Park lap times - FastestLaps.com

List of fastest lap times for Toronto Motorsports Park. Updated September 2024.

fastestlaps.com

You don't ever use launch control on a race track unless you're drag racing so optimizing the gear box to manage 2.8 seconds to 60 is just not relevant. If the car is so focused for track use and everything is so optimized, why have a 7th or an 8th gear? Two unwanted gears that just adds extra mass. You might use 6th gear for highway cruising but if you hit your top speed in 5th, then why does that matter? Perhaps having a 8 speed DCT on the spec sheet is more sellable than a mere 6 speed box.

GM doesn't even have to shorten the final drive. They can leave 1st and 2nd the way they are and just shorten the rest of the gears. Give me a reason to use those last few gears or get rid of that dead weight.



I daily a '23 M4 XD, it's very fast. S58 is a supped up version of B58 so it's as good as straight 6 is gonna get for the moment.

The gear ratios are by no means perfect. I suppose they are good enough for 0 to 60, but the primary reason the vette can't do faster than 2.8, regardless of trim or power, is traction. This guy has a fantastic explainer for why the theoretical 0 to 60 time of a C8 is 2.76 seconds, whether it's the base C8, Z06, or ZR1.



On another note, the 1st gear is, for the most part, unusable on a race track. You don't do any hard launches or start from a stand still on a proper track so you never go down to first. Most of the time, you don't even need to use 2nd as traction can be a problem on slow speed corners, specially on exit.

OP, you are again using Jason's whiteboard math to prove your napkin math, that's what I call conformation bias.

Think of it this way, C8 just like BMW cars is designed to do everything for everyone or else it would not sell so many units at such low prices. The vehicle has to not only accelerate quickly, it also needs to cruise at 130km/h bellow 2000 rpm. It has to corner like its on rails, but ride like an old school Cadillac down the straight county road. There is also a matter of in-gear acceleration, you may not care about launch control derived 0-60 in 2.8 sec in a C8, but that also gets you 3.5 sec 5-60, 1.9 sec 30-50, and 2.5 sec 50-70 (the metrics that most drivers use almost everyday).

A fun car, is never the fastest/quickest car, and a fastest/quickest car is not the fastest/quickest in all metrics of speed/ acceleration while being not as fun.
From your comments regarding useless gears in the trans should be removed as to remove extra useless weight tells be you don't fully comprehend how a transmission works. Gear ratios when combined with engine RPM range is what gives cars their "bandwidth" and the more you have the better the car drives.

if all you want to do is optimize the transmission for 2-3-2-3 shifts, you would ruin the car, and this is why GM or any manufacturer will never allow customers to pick it as an option.

I am surprised you decided to fixate on gear ratios to make the car more fun, and not the weight of the car as compared to the competition as that is the first thing people think of when fun car is discussed.

if GM sacrificed comfort and performance to make the C8 fun the way you propose, they would sell 1/10th of the cars and it would cost $500,000
Just look at bespoke GM T33 and T50, or Singer 911 DLS that cost way over $1,000,000 with weight of 2200lb and even they would not let you pick your own gear ratios in the transmission.

I hope you don't take offence, just like you, I love to nerd out on this stuff.

 

[Gottagofast]

OP, you are again using Jason's whiteboard math to prove your napkin math, that's what I call conformation bias.

Think of it this way, C8 just like BMW cars is designed to do everything for everyone or else it would not sell so many units at such low prices. The vehicle has to not only accelerate quickly, it also needs to cruise at 130km/h bellow 2000 rpm. It has to corner like its on rails, but ride like an old school Cadillac down the straight county road. There is also a matter of in-gear acceleration, you may not care about launch control derived 0-60 in 2.8 sec in a C8, but that also gets you 3.5 sec 5-60, 1.9 sec 30-50, and 2.5 sec 50-70 (the metrics that most drivers use almost everyday).

A fun car, is never the fastest/quickest car, and a fastest/quickest car is not the fastest/quickest in all metrics of speed/ acceleration while being not as fun.
From your comments regarding useless gears in the trans should be removed as to remove extra useless weight tells be you don't fully comprehend how a transmission works. Gear ratios when combined with engine RPM range is what gives cars their "bandwidth" and the more you have the better the car drives.

if all you want to do is optimize the transmission for 2-3-2-3 shifts, you would ruin the car, and this is why GM or any manufacturer will never allow customers to pick it as an option.

I am surprised you decided to fixate on gear ratios to make the car more fun, and not the weight of the car as compared to the competition as that is the first thing people think of when fun car is discussed.

if GM sacrificed comfort and performance to make the C8 fun the way you propose, they would sell 1/10th of the cars and it would cost $500,000
Just look at bespoke GM T33 and T50, or Singer 911 DLS that cost way over $1,000,000 with weight of 2200lb and even they would not let you pick your own gear ratios in the transmission.

I hope you don't take offence, just like you, I love to nerd out on this stuff.

I think you missed entirely what I was saying and went on with your own thoughts and biases.

Even the base eco boost Mustang with its 10 speed auto box let you pick between two separate rear axle ratios based on driver's preference, and that's a sub $50k vehicle, so your argument regarding multi million dollar vehicles is just not valid. Pretty sure if you ask Singer what gear ratios you want, they would gladly take your money and alter it to your specs.

I'll leave it here as I've already explained everything else in previous posts.

 

[DenisC8]

I think you missed entirely what I was saying and went on with your own thoughts and biases.

Even the base eco boost Mustang with its 10 speed auto box let you pick between two separate rear axle ratios based on driver's preference, and that's a sub $50k vehicle, so your argument regarding multi million dollar vehicles is just not valid. Pretty sure if you ask Singer what gear ratios you want, they would gladly take your money and alter it to your specs.

I'll leave it here as I've already explained everything else in previous posts.

yes ford mustang lets you pick from 2 rear end ratios (3.15 for economy and 3.55 for performance), same as C8 Stingray has 2 rear end ratios for non-z51 and z51 cars, but z06 same as mustang dark horse already comes with the ratio that is best for performance picked by brilliant engineers based on thousands of hour of testing multiple options and combinations.

I have a feeling that you are a young automotive enthusiast, going through the early stages of passion for cars, and with time you will enter the next stage that will make you rethink all the knowledge you got from YouTube.

 

[Gottagofast]

yes ford mustang lets you pick from 2 rear end ratios (3.15 for economy and 3.55 for performance), same as C8 Stingray has 2 rear end ratios for non-z51 and z51 cars, but z06 same as mustang dark horse already comes with the ratio that is best for performance picked by brilliant engineers based on thousands of hour of testing multiple options and combinations.

I have a feeling that you are a young automotive enthusiast, going through the early stages of passion for cars, and with time you will enter the next stage that will make you rethink all the knowledge you got from YouTube.

I've been driving for over 20 years, sim racing for 15, and been in love with cars for over 30, and as I mentioned above, I have the production car track record for TMP. I don't think stating that I might know a bit more about a motor vehicle than your average online commenter would be too much of a stretch.

Speaking of YouTube and the car content I watch, there has not been a single criticism regarding Z06's gearbox, and rightly so. I'm sure for the "average user" it's perfectly fine. The average user also do not track their car nor drive the vehicle on or over the limit like I tend to do when I'm on a track. To each their own I suppose.

I do agree that you can't please everyone and compromises have to be made.