fatsport

I've just started tracking my 17 GS Z07, 7 speed manual. It's balanced, poised, fun, forgiving. It runs cool, brakes are awesome, love the car. But the gearing is terrible. 2nd is too short except for very slow turns, 3rd is good, 4th is way too high, and 5th-7th are useless. How do you guys deal with it? I'm trying to learn to stay in a higher than optimum gear and focus on hitting my marks, rolling through the corner and getting back to the gas as early as possible. But when I come to a straight and no lift shift from 3rd to 4th the car just sits there.
For reference, here is the gear ratio and theoretical top speed - at 6600 rpm - in each gear:
1st - 2.97:1 ----51 mph
2nd - 2.07:1---- 74 mph
3rd - 1.43:1---- 106 mph
4th - 1.00:1----152 mph
5th - .71:1----215 mph
6th - .57:1----268 mph
7th - .48:1-----318 mph

I have no desire to buy a Z06. I live in South Florida, the heat doesn't stop. I have a friend who has a Z06, heat is all we ever talk about with his car. Gear ratios are great for the track in the Z06 though.

KnightDriveTV

Lots of compromises built in. That's a transmission geared to meet regulations and get the job done well enough.

TKOGTO

The C6 gearing in the A6 is quite similar except for 3rd. The theoretical top speed for the A6 in 3rd is 122mph. In practice it bogs down @ 117mph. If yours happens @ 106mph and is the same dog in 4th that mine is, I'd say I think I'm keeping my C6 for longer than I thought. On every track I run, whenever I wind 3rd out as far as it goes without bogging down (~6,250) my lap times are noticeably better than short shifting at 5,900 - 6,000.

Tadge had a reply a while back explaining the rationale behind the gearing. Readers Digest version: they opted for gearing for the masses, not us. Can't blame them. Just wish they could turn a profit on track focused version with all the bits and gearing we need.

Torch FRC

Possibly a little off topic but why does the C7 have 2 o/d gears?

fatsport

3 overdrive gears. It's pathetic. And 5th, the shortest one, is useless. Car goes nowhere. I know that 4th is set by the diff as it's 1:1, and how they want to keep it for packaging purposes. But 5th is a joke. Z06 5th is .82, GS/Z51 is .71. Z06 hits 5th at 5400 rpm, right in the power band. GS/Z51 hits 5th at 4650 rpm and the car dies. WTF
The car is basically a 5 speed.

67Ranger

The 2 OD gears are for fuel economy, so it can compete with the 8-10 speed automatics coming out.

PeteC7

Tadge pretty much said that 4th had to be 1:1 due to the trans architecture. You can read his whole response in the Ask Tadge section and since it was kept (4th being 1:1) in order to keep cost in-line I'm pretty much good with the decision. Personally I would have ditched 7th and stayed with a 6 speed though.

The downside is that yes it kind of falls on it's face shifting into 4th. I try to really focus on redlining in 3rd to try and get into 4th with the most speed possible. I did COTA for the first time this past weekend and the end of the long back straight I was full throttle in 4th for over 10 seconds! Since it was my first time I just hit the redline in 4th and braked a bit early as opposed to grabbing 5th for a split second. PDK Porsches would pull me pretty good there as they pop through a couple gears. It's just the nature of the car.

SocalC5Z

And I thought the gearing was bad in my C5Z...Why a 7 speed? They should have sacrificed top gear and made the rest close and usable. Who cares about the jump to a cruising OD top gear?

KnightDriveTV

Guys...read about the fuel mileage certification procedure...it requires the shift point, simulates traffic on the 405, etc...it's decades old in many ways. .The 1-4 skipshift, fleet fuel requirements, etc...all these things lead to the transmission evolution. The GM engineers don't want to build all this bs into these cars; they don't have a choice.

As stated...these transmissions are a very calculated balance of regulation and function.

96GS#007

taken19

To the OP...

What track are you driving? I've got a few thousand laps at Homestead with 4 different vettes (2 C5Z racecars, C6 Z51 heavily modded and now a C7 GS). I have only had the 17 GS for about 3 weeks now but had the opportunity to run it at HMS last weekend for 25-30 laps total. Car is stock down to the air filter, but there was no issue with gearing there. Shift points worked well for that track and I was in the 1:41's (road course, no banking) with all nannies on and plenty left in the car. That car has 1:38 in it on stock non-Cup tires with all nannies on, so gearing should not hold you back... at least not at HMS. PBIR or Sebring may be different as I haven't had enough seat time to bring the car there yet. Do you have any specific hardspots with the gearing/shift points so others might be able to help you?

Hope that helps provide insght for at least one track in South FL.
Sean

taken19

Also, why are you no-lift shifting? Relying on the fuel cutoff to keep your motor safe (and potentially car) doesn't sound like a smart move unless you have significant pay dirt as a reward for driving thiat way. Are you competing or just doing DE's?

Just my humble opinion...

truth.b

In my experience over time I've got use to th 3rd to 4th drop off in my c6 GS. But still one of my remedies has been to raise the redline about 200 RPM after I got headers. In practice the extra rpm gave me about 3-6MPH and I "feel" it helps with overall acceleration. Grant it it could all be in my head, but below are two vids before and after the change, I notice it most with the bridge straight. I'm not sure if a LT1 would far as well with the extra revs but you could ask around.

Before RPM change:



After RPM change:

fatsport

I disagree. Cheap, supply chain easy, was the calculation. The 7 speed in the C7 Z51 is just the C6 Z51 transmission with an even taller 7th gear added. That's the real reason imo.
They could have put a shorter 5th and 6th in there if they wanted too. 5th was a top speed gear for the C6, with 6th as an OD. Now that there are 7 gears, WTF are all the OD gears for?
The base Stingray has a more useful, lower 5th than the Z51/GS. Why isn't that in the GS and Z51 now, when you still have 2 airplane gears for gas mileage?
5th is geared for 215 mph, my car won't do 175 in Mexico. Why?

I agree. This would be my ideal solution. It was also GM's solution for the 1LE Camaro. It has the Z06 ratios, with a 3.73 rear end.

I've just done PBIR a couple times, going to Sebring next. The back straight takes forever, I could take a nap in 4th gear. It probably doesn't help that I've done the track on a 1000 Ninja. Additionally, there was a ZL1 10 speed there the last time I ran. I pointed him by between corners 5-6, and then caught him when entering the back straight, was right on his bumper. I could here is car shift 4 times as he pulled away on the back straight, while I only went from 3rd-4th.

fatsport

Quotes from 2 writers at Motor Trend, and their 2017 BDC test, where the Camaro ZL1 1LE was faster around a track
Also, the crowded seven-speed manual gearbox has rubbery, ropey throws and doesn't like to be rushed, and the gear ratios felt too tall for the track-oriented Grand Sport. Said executive editor Mark Rechtin: "It seems like there was a big gap between the powerbands in third and fourth gear."

Third gear is too short, but fourth is too long for many of the corners. I found myself cursing for having to upshift and then downshift again immediately after or for holding a gear too long because I knew I'd have to slow for the coming set of corners

Bill Dearborn

You have to go back to the C5 and it's Z06 gearing which is close to the C6 Z51 and the C7 Z51/GS. The C5Z was designed as an all around performer and the M12 transmission worked great in an autocross. Get out of 1st gear ASAP and run in 2nd. Then when the C6 with the LS2 came along they used that type of trans in it so it could be close to the C5Z in performance. When they went to the C7 Z51 the engine had the same power and torque curve as the C6 LS7 up to 4000 rpm. With the C7 Z51 weighing 200 lbs more than a C6Z and having 45 less HP they used the same short transmission gearing with the C7 Z51 to make it more competitive with the C6Z in lower speed events.

Bill

JHrinsin

Just a maybe crazy thought, but what about swapping to the close ratio TR6070 from the C7 Z06/ZR1 with the 2.291st to 0.82 5th gears? I know some friends of mine that race both C5/C6 that have swapped to the C6 ZR1 TR6060 with the 2.291st to 0.82 5th gears and found it to work much better on the larger/faster track than the wider ratio boxes.

fatsport

Great driving, and a significant improvement
I don't think I can raise the redline, as the AFM lifters add additional weight to the valve train. More gas mileage crap on a great car

fatsport

This will be the best solution. Ideally, with 3.90 gears that "Pumba" is working on. This would be awesome!

In the short term I need to become a better driver. I've got lots to learn.
Check out this lap by a C&D editor at VIR. Within a couple seconds of Tadge, and faster than any Z06 on this board. He uses the gears very well.

PRE-Z06