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[ANSWERED] Manual Transmission Gearing

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Old 04-29-2017, 01:19 AM
  #21  
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Originally Posted by WaxWeekly View Post
This is a bit surprising to me.

I've always assumed that the ratios were also a large part of marketing efforts. Having third gear end at 98 mph means you have another shift to hit 100.

Since marketing usually talks about 0-60 or 0-100 times, it makes sense that the gears should get you just past those marks for the best magazine racing.
Just let it go a few rpm past redline in third
Oems cheat, a lot. A certain manufacture I worked for, we put a smaller supercharger pulley on the cars we gave two magazines to test.
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Old 04-29-2017, 09:49 AM
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Originally Posted by village idiot View Post
Just let it go a few rpm past redline in third
Oems cheat, a lot. A certain manufacture I worked for, we put a smaller supercharger pulley on the cars we gave two magazines to test.
Redline in my Z51 and now my Grand Sport in 3td is ~103 mph. Can't go past redline without a tune-car turns off!

Now in my ProSteet Rod I do go a bit past redline with the 8.2 Liter BB to get best 0 to 60 times. Have rev limiter set 300 rpm over!
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Old 04-29-2017, 12:50 PM
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Yeah, if you wanted to test 0-100, you could just let it go to the rev limiter.
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Old 04-30-2017, 12:43 PM
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Sounds like Tadge agrees and would have preferred a shorter 4th gear, but one wasn't available that met the other requirements. It was a trade off. Looks like the Z06 gears are more optimum, but would like unit have been too expensive for the Z51?
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Old 04-30-2017, 12:49 PM
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It's pretty hard to come up with a reason not to have one of your gears (whichever it may be) 1:1. 1:1 is obviously direct drive. It's the most efficient gear.

Practicality of the rear diff size generally prohibits it, but in an ideal world, 1:1 would be 7th gear since it's the most efficient (and make the final drive ratio something like 7.5:1 or whatever). You'd get the best MPG.

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Old 05-01-2017, 09:45 AM
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Originally Posted by WaxWeekly View Post
This is a bit surprising to me.

I've always assumed that the ratios were also a large part of marketing efforts. Having third gear end at 98 mph means you have another shift to hit 100.

Since marketing usually talks about 0-60 or 0-100 times, it makes sense that the gears should get you just past those marks for the best magazine racing.
That transmission shifts fast enough it really doesn't matter where the shift point is at for that car.

Originally Posted by village idiot View Post
Having owned and driven a number of sports cars, I really love the tall gears in the Corvette. It really doesn't give up much at the track, the it makes it so much more drivable on the highway, and of course there are the benefits of longer life with less RPMs and better gas mileage.
While I agree with you at the same point that means there is no reason for this car to have 7 speeds. It was purely marketing. Could have been a simple 6 speed with two over drive gears.

The gear ratios work best for the Z06.
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Old 05-01-2017, 12:40 PM
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A little misinformation above on gearing, but you will ALWAYS have a 1:1 ratio in a manual transmission. That gear is where your power flow is straight through the case, not running any gears on the countershaft. I suppose that doesnt really have to be 4th, but a 1:1 does have to be in the trans someplace
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Old 05-01-2017, 09:04 PM
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Originally Posted by Nosferatu View Post
That transmission shifts fast enough it really doesn't matter where the shift point is at for that car.



While I agree with you at the same point that means there is no reason for this car to have 7 speeds. It was purely marketing. Could have been a simple 6 speed with two over drive gears.

The gear ratios work best for the Z06.
It's definitely not a track gear, but with the extra torque down low from vvt and DI, why not? Probably improved mpg a good amount.
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Old 05-02-2017, 09:05 AM
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Originally Posted by village idiot View Post
It's definitely not a track gear, but with the extra torque down low from vvt and DI, why not? Probably improved mpg a good amount.
owning both the C6 and C7 in manual I can tell you 5 & 6 in the C6 is just as good/equal as having 5 6 and 7 for overdrive when it comes to economy and convenience. It was pure marketing silliness. Let's have 7 gears but the car hits 150 in 4th and 5th will take the car to redline...

EDIT: 5th could have been 1:1 that took the car to 150 MPH.

These speeds for red line would have made more sense...

1st - 40 MPH (roughly the same)
2nd - 70 MPH (tad shorter)
3rd - 95 MPH (tad shorter)
4th - 125 MPH (def shorter)
5th - 150 MPH (your 1:1 gear)
6th - 175 MPH
7th - 200+ stupid tall gear

Last edited by Nosferatu; 05-02-2017 at 09:07 AM.
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Old 05-02-2017, 11:45 AM
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Originally Posted by Nosferatu View Post
owning both the C6 and C7 in manual I can tell you 5 & 6 in the C6 is just as good/equal as having 5 6 and 7 for overdrive when it comes to economy and convenience. It was pure marketing silliness. Let's have 7 gears but the car hits 150 in 4th and 5th will take the car to redline...

EDIT: 5th could have been 1:1 that took the car to 150 MPH.

These speeds for red line would have made more sense...

1st - 40 MPH (roughly the same)
2nd - 70 MPH (tad shorter)
3rd - 95 MPH (tad shorter)
4th - 125 MPH (def shorter)
5th - 150 MPH (your 1:1 gear)
6th - 175 MPH
7th - 200+ stupid tall gear
No thanks. Even the Stingray doesn't have a 1st gear that tops out at 40. That's just ridiculous. The Z06 makes it well past 60 in 1st. As it should be.
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Old 05-02-2017, 12:04 PM
  #31  
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Originally Posted by Nosferatu View Post
owning both the C6 and C7 in manual I can tell you 5 & 6 in the C6 is just as good/equal as having 5 6 and 7 for overdrive when it comes to economy and convenience. It was pure marketing silliness. Let's have 7 gears but the car hits 150 in 4th and 5th will take the car to redline...

EDIT: 5th could have been 1:1 that took the car to 150 MPH.

These speeds for red line would have made more sense...

1st - 40 MPH (roughly the same)
2nd - 70 MPH (tad shorter)
3rd - 95 MPH (tad shorter)
4th - 125 MPH (def shorter)
5th - 150 MPH (your 1:1 gear)
6th - 175 MPH
7th - 200+ stupid tall gear
I don't own a C7 but with the available torque in my stock C6 Grand Sport I wouldn't want the above shift points. Especially at VIR full course (home track), those shift points would put me at redline going through the uphill esses. no thank you.
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Old 05-02-2017, 02:55 PM
  #32  
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Originally Posted by Nosferatu View Post
owning both the C6 and C7 in manual I can tell you 5 & 6 in the C6 is just as good/equal as having 5 6 and 7 for overdrive when it comes to economy and convenience. It was pure marketing silliness. Let's have 7 gears but the car hits 150 in 4th and 5th will take the car to redline...

EDIT: 5th could have been 1:1 that took the car to 150 MPH.

These speeds for red line would have made more sense...

1st - 40 MPH (roughly the same)
2nd - 70 MPH (tad shorter)
3rd - 95 MPH (tad shorter)
4th - 125 MPH (def shorter)
5th - 150 MPH (your 1:1 gear)
6th - 175 MPH
7th - 200+ stupid tall gear


First gear tops out at 58 (meaning they can probably hit 60mph before the rev limiter). They probably had 0-60 in mind with that gear selection, if I had to guess.


Stingray redline MPH by gear:
I: 58
II: 86
III: 119
IV: 154
V: 208
VI: 308
VII: 367
You're basically proposing making the old 4th gear the new 5th gear, 6th a steeper 5th and 7th stays as 7th (or maybe 6.5). I generally don't mind widely spaced overdrive/cruising gears, but man- going from 5 to 7 is kind of a big jump.

It's obviously more oriented for road racing than drag racing. Drag racing needs steeper first gear to get out of the hole in the powerband. IE: If you want to launch at 4k rpm, you want a short 1st gear so you're only asking your tires to grip a near instant 0-20mph change rather than a 0-40mph change. You're generally more limited by your tire, so it would force you to bog the engine out of the hole or launch below your power band with tall gears.

In road racing, you're basically never below 50mph, so a first gear that ends below (or near) that is basically a waste of a gear. Dedicated road race cars can barely get going because first gear is so tall (and the clutch is all or nothing).

Also, for durability and driveability, shorter first gear is nice. Clutch, like tires in a drag race, is under less stress and it's just smoother launching for daily driving (idle to go is 0-5mph instead of 0-10mph)


I just with the Z51 kept the same 6th and 7th as the non-z51. Other than that, I like the gearing. It works very well at the track. 2nd could be slightly taller so the 3-2 isn't as abrupt, but revmatching mostly handles that.

My REAL wish is that the shift pattern went "euro"
R246
1357

This way at the track, when I'm basically only using 2 and 3, I can just keep going straight up and down.

Last edited by village idiot; 05-02-2017 at 02:56 PM.
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Old 05-02-2017, 03:23 PM
  #33  
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Originally Posted by village idiot View Post
My REAL wish is that the shift pattern went "euro"
The proper name is "dog leg", and I agree completely. But the 0-60 and quarter mile guys would scream bloody murder.
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Old 05-03-2017, 09:22 AM
  #34  
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Originally Posted by truth.b View Post
I don't own a C7 but with the available torque in my stock C6 Grand Sport I wouldn't want the above shift points. Especially at VIR full course (home track), those shift points would put me at redline going through the uphill esses. no thank you.
Then keep 1 2 and 3 where they're at but just watch the video above when the car shifts to 4th and especially to 5th it just runs out of grunt. It drops WAY out of the power band. 4th should end around 130 (and not 150) and 5th around 155 (give the car a minimally taller rear gear to up the MPH from 150 to 155 in the 1:1 gear). 6th should take the car to 180/185 MPH, call this the top speed of the car, and keep your stupid tall 7th for fuel economy.

Having a gap from 100 to 150 for one gear in a N/A car is silly.

Non-Z51 spacing works better when you have a lot of power (e.g. my old boosted C6 was non-Z51). It worked having 3rd go to 115 and then 4th to 150. It kept the RPMs higher going into 4th since 3rd pulled to a much higher speed. Once again, however, shifting into 5th the car bogged and fell out of the power band. Definitely was noticeable in the 1/2 mile racing events. Car pulls strong to 150, shift into 5th...and

EDIT: Up until the 7th 1:1 gear (I'm assuming) this sucker stays in the power band until the shift at 145 MPH...It's not as bad of a drop but could have made them a hair closer.

Last edited by Nosferatu; 05-03-2017 at 09:28 AM.
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Old 05-03-2017, 11:25 AM
  #35  
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The correct way to do that is to make gear 3 slightly taller
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Old 05-03-2017, 11:56 AM
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Originally Posted by village idiot View Post
The correct way to do that is to make gear 3 slightly taller
Then there's still no need for a 7 speed in the C7 given how wide and tall the gearing is on the car to begin with. 5th gets the car to top speed, 6th for fuel. Complicating with 7 speeds was a marketing gimmick to copy Porsche.

Porsche at least has the gearing better overlap with their 7 speeds in both automatic and manual configurations. They use the equivalent of a 5th gear 1:1 ratio, top speed is 6th gear, and 7th is straight up fuel economy. 5th is still usable on the Porsche 7 speed cars but 5th will not even hit redline on the Vette due to lack of power it craps out in 5th.

Porsche AUTO (7 speed PDK):
Gear Ratio Overall ratio (Rpm) Mph
1st 3.91:1 13.45:1 (7800) 46
2nd 2.29:1 7.88:1 (7800) 79
3rd 1.65:1 5.68:1 (7800) 109
4th 1.30:1 4.47:1 (7800) 139
5th 1.08:1 3.72:1 (7800) 167
6th 0.88:1 3.03:1 est (7200) 189*
7th 0.62:1 2.13:1 na
Final drive ratio 3.44:1

Porsche MANUAL (7 speed):
1st 3.91/6.0 47mph 7800rpm
2nd 2.29/10.2 79mph 7800rpm
3rd 1.55/15.0 117mph 7800rpm
4th 1.30/17.9 140mph 7800rpm
5th 1.08/21.6 168mph 7800rpm
6th 0.88/26.5 180mph 6794rpm
7th 0.71/32.8 180mph(claimed) 5481rpm
Final drive ratio 3.44
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Old 05-03-2017, 12:32 PM
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^^^ Yeah, because Porsche always beats Corvette.
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Old 05-03-2017, 12:57 PM
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I really like my 7th gear. I cruise at 80mph barely idling. I actually wish it was taller, hence my request that it have non-Z51 gearing in 7th.


good for NVH
good for mpg
good for durabily

What's not to like about it?

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Old 05-03-2017, 02:00 PM
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Originally Posted by Nosferatu View Post
Then keep 1 2 and 3 where they're at but just watch the video above when the car shifts to 4th and especially to 5th it just runs out of grunt. It drops WAY out of the power band. 4th should end around 130 (and not 150) and 5th around 155 (give the car a minimally taller rear gear to up the MPH from 150 to 155 in the 1:1 gear). 6th should take the car to 180/185 MPH, call this the top speed of the car, and keep your stupid tall 7th for fuel economy.

Having a gap from 100 to 150 for one gear in a N/A car is silly.

Non-Z51 spacing works better when you have a lot of power (e.g. my old boosted C6 was non-Z51). It worked having 3rd go to 115 and then 4th to 150. It kept the RPMs higher going into 4th since 3rd pulled to a much higher speed. Once again, however, shifting into 5th the car bogged and fell out of the power band. Definitely was noticeable in the 1/2 mile racing events. Car pulls strong to 150, shift into 5th...and

EDIT: Up until the 7th 1:1 gear (I'm assuming) this sucker stays in the power band until the shift at 145 MPH...It's not as bad of a drop but could have made them a hair closer.




If Corvette was designed around maximum straight line acceleration than I would agree but it is more geared towards road course work and everyday driving. Which for me short gears suck and can be more detrimental to laptimes than beneficial with the exception of automatic (DCT) trans where the shift shock between gears is controlled by a computer.


For me the only me the only gear I would change in the Z51/GS cars would be 3rd. I would stretch out a bit so that it redlined at 112-115 instead of 107. You'll notice in the vid below I short shift 3rd @ the 1:xx mark (100MPH) to help with keep the car balanced while setting up for the uphill esses of track. Going with a much shorter 3rd & 4th could mean an extra shift and/or more difficulty in managing torque at moderately low triple digit speeds.



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Old 05-03-2017, 05:24 PM
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Originally Posted by truth.b View Post
If Corvette was designed around maximum straight line acceleration than I would agree but it is more geared towards road course work and everyday driving. Which for me short gears suck and can be more detrimental to laptimes than beneficial with the exception of automatic (DCT) trans where the shift shock between gears is controlled by a computer.


For me the only me the only gear I would change in the Z51/GS cars would be 3rd. I would stretch out a bit so that it redlined at 112-115 instead of 107. You'll notice in the vid below I short shift 3rd @ the 1:xx mark (100MPH) to help with keep the car balanced while setting up for the uphill esses of track. Going with a much shorter 3rd & 4th could mean an extra shift and/or more difficulty in managing torque at moderately low triple digit speeds.
I agree. I'd like a slightly longer 3rd. Just a touch longer.

Nice wheeling. You seem to get on the gas good and early, but you seem to coast a lot rather than staying on the gas and braking harder.

What recording system is that?

Last edited by village idiot; 05-03-2017 at 05:25 PM.
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