performance axle ratio
Race Director
Joined: Dec 2011
Posts: 10,355
Likes: 12
When projecting limited top speed based upon rear end gear ratio, my thinking was colored by the situation where guys used to put 4:56 rear ends in their cars for extreme drag acceleration but were penalized at top end out on the highway. Without the limiter, would the LS2 and LS3 cars, in fact, reach highest speed in highest gear? (assuming long enough straight flat track)
Safety Car
Joined: Aug 2012
Posts: 3,960
Likes: 1,106
For highest terminal speed the gearing should be chosen so that the engine is running fully loaded at its peak HP RPM which definitely won't be while in the third overdrive gear in a C7 
I haven't kept up with it in years but a lot of the European cars used to be set up where this situation occurred in the next to highest available transmission gear.
I haven't kept up with it in years but a lot of the European cars used to be set up where this situation occurred in the next to highest available transmission gear.
Team Owner
Joined: Sep 2000
Posts: 25,015
Likes: 2,709
From: Far NW 'burbs of Chicago
St. Jude Donor '13
C6-
Both the A6 and the M6 are said to reach top speed in 5th gear. My not-quite that-fast-but-close experience, and the gear/speed tables, agree. That's for both our previous LS2 A6 2.56 and current LS3 A6 2.73
Both the A6 and the M6 are said to reach top speed in 5th gear. My not-quite that-fast-but-close experience, and the gear/speed tables, agree. That's for both our previous LS2 A6 2.56 and current LS3 A6 2.73
Melting Slicks
Joined: Jun 2004
Posts: 2,130
Likes: 54
From: Granbury, Pecan Plantation TX
I believe buying the C7/Z51 with the A6 trans will be the same as buying a C6 GS with the A6 trans:
The C6 Base / A6 has a 2.56 axle ... The C6 GS / A6 has a 2.73 axle
The C7 Base / A6 has a 2.56 axle ... The C7 Z51 / A6 has a 2.73 axle
In fact, here are the extras that come with the C7 Z51 when ordered with the A6 transmission:
Q7S Split-Spoke Silver Painted Aluminum Wheels, 19” x 8.5” (front), 20” x 10” (rear)
Michelin Pilot Super Sport ZP Tires, P245/ 35ZR-19” (front), P285/ 30ZR-20” (rear)
Brembo Performance Brakes w/ Black Calipers
Performance Suspension
Dry Sump Oil System
Electronic Limited Slip Differential w/ 2.73 Performance Axle Ratio
Differential Oil Cooler
Unique Full-Width Rear Spoiler
___________________________________
.
The C6 Base / A6 has a 2.56 axle ... The C6 GS / A6 has a 2.73 axle
The C7 Base / A6 has a 2.56 axle ... The C7 Z51 / A6 has a 2.73 axle
In fact, here are the extras that come with the C7 Z51 when ordered with the A6 transmission:
Q7S Split-Spoke Silver Painted Aluminum Wheels, 19” x 8.5” (front), 20” x 10” (rear)
Michelin Pilot Super Sport ZP Tires, P245/ 35ZR-19” (front), P285/ 30ZR-20” (rear)
Brembo Performance Brakes w/ Black Calipers
Performance Suspension
Dry Sump Oil System
Electronic Limited Slip Differential w/ 2.73 Performance Axle Ratio
Differential Oil Cooler
Unique Full-Width Rear Spoiler
___________________________________
.
Team Owner
Joined: Feb 2001
Posts: 27,254
Likes: 136
From: Short Hills, NJ
Not to get off the subject of Top speed and gear ratios, but looking at the order guide option MYC (If on the actual order guide you select the blue MYC) MYC 6L80 shows a max torque figure of 439, those are the same specs as the 13 and before. Being the estimates for the C7 is getting us 450 ~ 460 is there any word on what they are doing to beef up the 6L80 to handle it, or are they going to use TM to limit the torque, therefore we will not reap the benefit of the additional torque.
It could be a variation of the CTS-V's/ZL1's 6L90 as well.
Moderator
Joined: Feb 2006
Posts: 39,115
Likes: 17,971
From: DFW Area TX
Not to get off the subject of Top speed and gear ratios, but looking at the order guide option MYC (If on the actual order guide you select the blue MYC) MYC 6L80 shows a max torque figure of 439, those are the same specs as the 13 and before. Being the estimates for the C7 is getting us 450 ~ 460 is there any word on what they are doing to beef up the 6L80 to handle it, or are they going to use TM to limit the torque, therefore we will not reap the benefit of the additional torque.
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Safety Car
Joined: Jun 2004
Posts: 4,430
Likes: 81
From: Whidbey Island WA
A transmissions rating is whatever the manufacturer says, it is not a standard and often positioned rather than being a real estimate of the maximum torque its likely to hold reliably. Based on the number of C6s humming along just fine with long tubes in those automatic cars I'm thinking it could probably survive just fine through its swan song year with nothing more than an update to its "rating". Another thing to keep in mind is that we know for sure there is new programming and that they have made some valve body changes which by themselves would possibly add some extra headroom if they acted to help lower temps.