View Poll Results: Best transmission gear ratios for a LS2/LS3 C6
Z51 (Wide Ratio)
15
55.56%
Base (Close Ratio)
12
44.44%
Voters: 27. You may not vote on this poll
Close ratio (Base/Z06) vs Wide ratio (Z51) Gears
12-27-2011, 04:12 PM
#1
Burning Brakes
Thread Starter
Close ratio (Base/Z06) vs Wide ratio (Z51) Gears
Anyone with experience owning both transmissions, please chime in.
I originally was looking for a Z51 car and ended up finding a great deal on a base car. Now after owning a base car for about a year I am finding the "close ratio" transmission unnecessary for an engine with such a wide tq curve (LS2).
Now in all fairness I have only driven Z51 cars, I have not owned one. For street driving, the base car which has the ability to go 65 in 1st or 90 in 2nd doesn't seem as important as having a little more grunt to get out of the hole. Since rear end gears are a popular upgrade it would seem I am not the only one who thinks the C6 could use a deeper gear. For track driving I could understand why one may prefer the close ratio...
If I understand this correctly the Z51 tranmission's first three gears are deeper than the base trans and then has a bigger jump to the 1:1 fourth gear. Z51 owners: Do you feel the engine falls off power between third and fourth?
To those who have experience with both; what gear set is a better match to the LS2/LS3 for street driving? The difference may be nuanced, because its not like my base transmission car is a slouch out of the hole!
Still I would be interested in hearing opinions, hell lets make it a poll. Fire away
I originally was looking for a Z51 car and ended up finding a great deal on a base car. Now after owning a base car for about a year I am finding the "close ratio" transmission unnecessary for an engine with such a wide tq curve (LS2).
Now in all fairness I have only driven Z51 cars, I have not owned one. For street driving, the base car which has the ability to go 65 in 1st or 90 in 2nd doesn't seem as important as having a little more grunt to get out of the hole. Since rear end gears are a popular upgrade it would seem I am not the only one who thinks the C6 could use a deeper gear. For track driving I could understand why one may prefer the close ratio...
If I understand this correctly the Z51 tranmission's first three gears are deeper than the base trans and then has a bigger jump to the 1:1 fourth gear. Z51 owners: Do you feel the engine falls off power between third and fourth?
To those who have experience with both; what gear set is a better match to the LS2/LS3 for street driving? The difference may be nuanced, because its not like my base transmission car is a slouch out of the hole!
Still I would be interested in hearing opinions, hell lets make it a poll. Fire away
Last edited by Shifter6; 12-27-2011 at 04:16 PM.
12-28-2011, 10:57 AM
#4
CF Senior Member
Member Since: Feb 2006
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The difference between gearboxes isn't huge but GM engineered the gear ratios for a purpose. The Z06 gearbox (same as the 'base' C6) is better suited for road racing. The Z51 gearing was designed for the parking lot autocross enthusiast. I believe the Z51 tranny has a 5.32:1 spread from low to high (2.97:1 from low to 4th). The Z06 and 'base' C6 has a 5.21:1 spread from low to high (2.66:1 from low to 4th). Road racing cars often have a closer ratio gearbox (at least relative to the Z06/base C6 compared to the Z51 option) which is especially important in 1st through 4th gears. Closer ratios mean the engine can be kept closer to its power peak in flat-out road racing. Not unlike a 'granny' gear in a truck, the wider ratio Z51 gearbox gives it a slight advantage in those short parking lot autocross bursts. Again, the difference between the two isn't huge but I strongly perfer the closer ratio 'base' C6 (same as the Z06) gearing.
I'm not a drag racer (and maybe someone will say for sure) but I'd guess a Z51 option C6 would have to shift into 4th gear before crossing the 1/4 mile line. The Z06 or base C6 gearbox is likely still pushing hard in 3rd gear as it crosses the line. The initial 1st/2nd gear burst from the Z51 gives it a couple tenths of the second advantage in a 1/4 mile drag race but that's not enough to outweight the advantages of the 'base'/Z06 gearing on a road course for me.
I'm not a drag racer (and maybe someone will say for sure) but I'd guess a Z51 option C6 would have to shift into 4th gear before crossing the 1/4 mile line. The Z06 or base C6 gearbox is likely still pushing hard in 3rd gear as it crosses the line. The initial 1st/2nd gear burst from the Z51 gives it a couple tenths of the second advantage in a 1/4 mile drag race but that's not enough to outweight the advantages of the 'base'/Z06 gearing on a road course for me.
12-28-2011, 11:08 AM
#5
Team Owner
I'm not a drag racer (and maybe someone will say for sure) but I'd guess a Z51 option C6 would have to shift into 4th gear before crossing the 1/4 mile line. The Z06 or base C6 gearbox is likely still pushing hard in 3rd gear as it crosses the line. The initial 1st/2nd gear burst from the Z51 gives it a couple tenths of the second advantage in a 1/4 mile drag race but that's not enough to outweight the advantages of the 'base'/Z06 gearing on a road course for me.
At 6500 rpm, the base C6 tranny is doing approx. 114 mph. That's slightly under what some forum members have done.
At 6500 rpm, the Z51 equipped C6 is doing only about 104 mph.
So the fastest base C6 drivers would be in 4th gear, just like the Z51-equipped C6 drivers would be.
http://mysite.verizon.net/foofoo2/c6/
12-28-2011, 11:09 AM
#7
Melting Slicks
Member Since: Apr 2005
Location: ---Phoenix, AZ --- Boiler Up, Hammer Down!
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For street driving, the base car which has the ability to go 65 in 1st or 90 in 2nd doesn't seem as important as having a little more grunt to get out of the hole. Since rear end gears are a popular upgrade it would seem I am not the only one who thinks the C6 could use a deeper gear. For track driving I could understand why one may prefer the close ratio...
For street driving, the base car which has the ability to go 65 in 1st or 90 in 2nd doesn't seem as important as having a little more grunt to get out of the hole. Since rear end gears are a popular upgrade it would seem I am not the only one who thinks the C6 could use a deeper gear. For track driving I could understand why one may prefer the close ratio...
12-28-2011, 11:13 AM
#8
Burning Brakes
Thread Starter
The difference between gearboxes isn't huge but GM engineered the gear ratios for a purpose. The Z06 gearbox (same as the 'base' C6) is better suited for road racing. The Z51 gearing was designed for the parking lot autocross enthusiast. I believe the Z51 tranny has a 5.32:1 spread from low to high (2.97:1 from low to 4th). The Z06 and 'base' C6 has a 5.21:1 spread from low to high (2.66:1 from low to 4th). Road racing cars often have a closer ratio gearbox (at least relative to the Z06/base C6 compared to the Z51 option) which is especially important in 1st through 4th gears. Closer ratios mean the engine can be kept closer to its power peak in flat-out road racing. Not unlike a 'granny' gear in a truck, the wider ratio Z51 gearbox gives it a slight advantage in those short parking lot autocross bursts. Again, the difference between the two isn't huge but I strongly perfer the closer ratio 'base' C6 (same as the Z06) gearing.
I'm not a drag racer (and maybe someone will say for sure) but I'd guess a Z51 option C6 would have to shift into 4th gear before crossing the 1/4 mile line. The Z06 or base C6 gearbox is likely still pushing hard in 3rd gear as it crosses the line. The initial 1st/2nd gear burst from the Z51 gives it a couple tenths of the second advantage in a 1/4 mile drag race but that's not enough to outweight the advantages of the 'base'/Z06 gearing on a road course for me.
I'm not a drag racer (and maybe someone will say for sure) but I'd guess a Z51 option C6 would have to shift into 4th gear before crossing the 1/4 mile line. The Z06 or base C6 gearbox is likely still pushing hard in 3rd gear as it crosses the line. The initial 1st/2nd gear burst from the Z51 gives it a couple tenths of the second advantage in a 1/4 mile drag race but that's not enough to outweight the advantages of the 'base'/Z06 gearing on a road course for me.
I wonder to about 60mph or 100mph, which is faster? If the Z51 can make it to 60 in first, I would think it would be quicker. I would guess to 100mph the Z51 would have an advantage. It would be in the "meat" of 3rd gear while the base car would be just getting into 3rd gear.
Again relativley speaking it seems when a car can go 65mph in 1st or 90 in second its over geared. And that when you have an high torque engine like a LS2 or LS3 it would be better suited to a slightly wider ratio. Almost all driving is done below 100mph and slightly deeper gears in that range might add to the fun.?
Still its not like my base tranny car has any problem setting fire to the goodyears. With temps in the 50s a fast shift to second will set them a blaze.
12-28-2011, 11:15 AM
#9
Team Owner
In 2005 I bought a Z51 coupe which I had for seven months, then found a deal I couldn't pass up on a convertible with F55 which has the "base" transmission.
I could tell right away pulling away from a stop that the Z51 with the lower first gear was easier to get the car moving without as much clutch slip. Not a big deal, but it was noticeable at first.
BTW, I ran them both in the quarter mile. If you were to look at the times and analyze them, you would see that for all practical purposes there was no difference in my times. I was slightly (and I mean slightly) faster in the Z51, but it was so close that it can be chalked up to variations in weather and in my ability to launch them. I also had a friend at the time with a Z51 and I can tell you that I outran him in a head to head race, but I can't discuss the details on the forum.
To address a couple of comments above, at the drag strip I had to shift them both to fourth. On one run in the non-Z51 I tried to hold third as it hit the limiter crossing the finish - it was my slowest run. If you look at the "fast list", times for both cars should still be on there. To be fair, the convertible had a B&B exhaust, but I truthfully believe it added nothing - but it's on a different list as it's considered a modded car to the forum.
I could tell right away pulling away from a stop that the Z51 with the lower first gear was easier to get the car moving without as much clutch slip. Not a big deal, but it was noticeable at first.
BTW, I ran them both in the quarter mile. If you were to look at the times and analyze them, you would see that for all practical purposes there was no difference in my times. I was slightly (and I mean slightly) faster in the Z51, but it was so close that it can be chalked up to variations in weather and in my ability to launch them. I also had a friend at the time with a Z51 and I can tell you that I outran him in a head to head race, but I can't discuss the details on the forum.
To address a couple of comments above, at the drag strip I had to shift them both to fourth. On one run in the non-Z51 I tried to hold third as it hit the limiter crossing the finish - it was my slowest run. If you look at the "fast list", times for both cars should still be on there. To be fair, the convertible had a B&B exhaust, but I truthfully believe it added nothing - but it's on a different list as it's considered a modded car to the forum.
Last edited by jschindler; 12-28-2011 at 11:19 AM.
12-28-2011, 11:17 AM
#10
Burning Brakes
Thread Starter
12-28-2011, 11:35 AM
#11
Team Owner
Per my post above, my 1/4 mile times for the non-Z51 car I had are not listed anymore. But here is what I posted the day I ran the convertible at the track and compared it to my Z51 coupe. Remember, these were both 2005's. The Z51 was a coupe, and the non-Z was a convertible with a cat-back B&B exhaust. BTW, in the coupe I ran a 12.5 at 114.5.
Okay, I finally got the "current C6" to the track tonight. As a little history, you see my time posted in the above threads. That was a year ago in the C6 Z51 coupe I had. Six months ago I traded it for a F55 convertible (six speed still). Conditions were good today, so I decided it was time to run it.
The car is stock except for the B&B Bullet exhaust. I still have the stock non-Z51 tires and ran them at 27# cold (about 29 at the track). Temperature was 60 degrees, no wind, low humidity and pressure about 30.15 and the track is at 24' elevation. Yes, I know - this is ideal!
Here is the Short version:
12.574 at 113.04. My 60' was a very mediocre 2.034. 1/8 mile was 8.225 at 89.54.
Long version:
Remember that it is a convertible, and I can never be sure if they will allow me to make more than one run because of no roll bar. First run, I bogged it pretty bad, so I backed off. If they were not going to let me run, I didn't want to waste it on that one.
Second run - clutch only came about half way up. I've heard of this, but it has never happened to me. Needless to say I aborted the run.
Third run - still not many folks at the track, so I got back in the staging area pretty quick. Fortunately, they had to clean up an oil spill on the track, so I had about a 20 minute cool down with the hood up. This made me feel pretty good about the clutch sticking. Ran the time I listed above.
Fourth run - when I came back from the third run, there were about 50 cars in line! Damn!!! This was also my first time in the left lane, so traction was unknown. Also, I decided to hold third gear (I shifted to fourth on the last run). Remember that a non-Z51 six speed redlines at about 114 in third. Traction was not as good. I ran a 2.074 60', and roasted the tires pretty good on the 1-2 shift. Also, holding third gear hit the rev limiter at the traps, which seemed to back my speed down. I only ran a 12.82 at 112.99.
That was it - done for the night. I feel good that I can now say I have had two C6's in the 12.5's. But I'm frustrated in that I feel certain that with more runs I could have gotten into the 12.4's. I have always gotten into the 1.95 range on my 60's. I should have lowered the pressure in the tires. Also, I would have shifted to fourth again - and run in the right lane!!!
One thing of interest. Comparing this car to the night I ran the 12.499 in the coupe, my best 1/8th time tonight was very much in line with most of my runs in the coupe, and the 1/8 speed was almost as good as my best in the coupe (89.54 in the vert, 89.95 in the coupe). What this tells me is that pulling the taller 3rd gear might be the biggest obstacle with the non-Z51.
By the way, I realize the B&B exhaust may be worth a little, feel free to factor that in however you wish.
All in all, no complaints though.
The car is stock except for the B&B Bullet exhaust. I still have the stock non-Z51 tires and ran them at 27# cold (about 29 at the track). Temperature was 60 degrees, no wind, low humidity and pressure about 30.15 and the track is at 24' elevation. Yes, I know - this is ideal!
Here is the Short version:
12.574 at 113.04. My 60' was a very mediocre 2.034. 1/8 mile was 8.225 at 89.54.
Long version:
Remember that it is a convertible, and I can never be sure if they will allow me to make more than one run because of no roll bar. First run, I bogged it pretty bad, so I backed off. If they were not going to let me run, I didn't want to waste it on that one.
Second run - clutch only came about half way up. I've heard of this, but it has never happened to me. Needless to say I aborted the run.
Third run - still not many folks at the track, so I got back in the staging area pretty quick. Fortunately, they had to clean up an oil spill on the track, so I had about a 20 minute cool down with the hood up. This made me feel pretty good about the clutch sticking. Ran the time I listed above.
Fourth run - when I came back from the third run, there were about 50 cars in line! Damn!!! This was also my first time in the left lane, so traction was unknown. Also, I decided to hold third gear (I shifted to fourth on the last run). Remember that a non-Z51 six speed redlines at about 114 in third. Traction was not as good. I ran a 2.074 60', and roasted the tires pretty good on the 1-2 shift. Also, holding third gear hit the rev limiter at the traps, which seemed to back my speed down. I only ran a 12.82 at 112.99.
That was it - done for the night. I feel good that I can now say I have had two C6's in the 12.5's. But I'm frustrated in that I feel certain that with more runs I could have gotten into the 12.4's. I have always gotten into the 1.95 range on my 60's. I should have lowered the pressure in the tires. Also, I would have shifted to fourth again - and run in the right lane!!!
One thing of interest. Comparing this car to the night I ran the 12.499 in the coupe, my best 1/8th time tonight was very much in line with most of my runs in the coupe, and the 1/8 speed was almost as good as my best in the coupe (89.54 in the vert, 89.95 in the coupe). What this tells me is that pulling the taller 3rd gear might be the biggest obstacle with the non-Z51.
By the way, I realize the B&B exhaust may be worth a little, feel free to factor that in however you wish.
All in all, no complaints though.
Last edited by jschindler; 12-28-2011 at 11:37 AM.
12-28-2011, 11:39 AM
#12
Melting Slicks
i owned a 06 Z, and currently own a 09 c6 z51, csc, and i really like the new trans and short shifter...i think for the street it has been much smoother and easier to shift in all gears..the CAGS is less intrusive and the shifts seem less notchy...
course there is a big difference in Hp and Tq from the Z to the c6, but the taller ratio's with the ls3 engine vs the ls7 with the older style trans on the street is a toss up. i enjoy the newer design in my 09 ls3 trans for all around driving than i did with the 06 Z..pic of both cars..
currently..
my old monster..
by the way the 06 Z is for sale...guy i sold it to, wants to sell has 25k mi on it.
bud
course there is a big difference in Hp and Tq from the Z to the c6, but the taller ratio's with the ls3 engine vs the ls7 with the older style trans on the street is a toss up. i enjoy the newer design in my 09 ls3 trans for all around driving than i did with the 06 Z..pic of both cars..
currently..
my old monster..
by the way the 06 Z is for sale...guy i sold it to, wants to sell has 25k mi on it.
bud
12-28-2011, 12:03 PM
#14
According to: http://mysite.verizon.net/foofoo2/c6/
A base manual C6 max speed in gears at 6500 rpms.
1st: 55 mph
2nd: 83 mph
3rd: 114 mph
A ZO6 max speed in gears at 7000 rpms.
1st: 60 mph
2nd: 90 mph
3rd: 123 mph
A Z51 optioned manual C6 or GS max speed in gears at 6500 rpms.
1st: 50 mph
2nd: 71 mph
3rd: 103 mph
A base manual C6 max speed in gears at 6500 rpms.
1st: 55 mph
2nd: 83 mph
3rd: 114 mph
A ZO6 max speed in gears at 7000 rpms.
1st: 60 mph
2nd: 90 mph
3rd: 123 mph
A Z51 optioned manual C6 or GS max speed in gears at 6500 rpms.
1st: 50 mph
2nd: 71 mph
3rd: 103 mph
Last edited by ultraman; 12-28-2011 at 12:08 PM.
12-28-2011, 01:05 PM
#15
Melting Slicks
yes, w/ the z51 its 50 mph in 1st gear...i just look at my HUD speed and at 50 i shift, and whada know, its at redline.....the feel is much like my 04 z06, about 50mph in 1st, and it gets there good and quick....:
oh, i might as well show a pic of my 04 Z that i used to own.....
bud
oh, i might as well show a pic of my 04 Z that i used to own.....
bud
Last edited by bud miller; 12-28-2011 at 01:07 PM.
12-28-2011, 01:26 PM
#17
Burning Brakes
Thread Starter
According to: http://mysite.verizon.net/foofoo2/c6/
A base manual C6 max speed in gears at 6500 rpms.
1st: 55 mph
2nd: 83 mph
3rd: 114 mph
A ZO6 max speed in gears at 7000 rpms.
1st: 60 mph
2nd: 90 mph
3rd: 123 mph
A Z51 optioned manual C6 or GS max speed in gears at 6500 rpms.
1st: 50 mph
2nd: 71 mph
3rd: 103 mph
A base manual C6 max speed in gears at 6500 rpms.
1st: 55 mph
2nd: 83 mph
3rd: 114 mph
A ZO6 max speed in gears at 7000 rpms.
1st: 60 mph
2nd: 90 mph
3rd: 123 mph
A Z51 optioned manual C6 or GS max speed in gears at 6500 rpms.
1st: 50 mph
2nd: 71 mph
3rd: 103 mph
Even so, 83 mph is very fast for 2nd out of 6 gears.
Again, it would seem the only downside of a Z51 ratio transmission would be the larger step between third and fourth. Z51 owners; do you feel the motor falls out of power, or the ratios are less than optimal? According to the chart, in a z51 shifting at redline from thrid to fourth brings the engine down to 4500rpms. On a base car it drops to 5000.
Last edited by Shifter6; 12-28-2011 at 01:30 PM.
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12-28-2011, 01:54 PM
#20
Burning Brakes
Thread Starter
Yeah, lets stick to gear ratios.
Mybe someone with more drag racing experience can pipe in, but to achieve maximum acceleration you want to keep the engine as close to peak torque as possible, right? If peak torque occurs at 4500rpms in a LS2/LS3 wouldn't the wide ratio tranny have a more optimal 3rd-4th shift?