6th gear top speed
Banned Scam/Spammer
Joined: May 2007
Posts: 15,685
Likes: 1,330
From: Machineguns, because I don’t compromise
There is very little bearing support for 6th gear so if you try it you'll damage the transmission Sooner than later. 
Top Speed for 6th gear on the M6 or M12 doesn't exist, it's for Fuel Economy on the interstate.
Top Speed for 6th gear on the M6 or M12 doesn't exist, it's for Fuel Economy on the interstate.
Drifting
Joined: Apr 2003
Posts: 1,389
Likes: 10
From: Jacksonville FL
You can get a higher speed in sixth with enough power. At 600 rwhp I've taken 5th to 7k rpm and shifted to 6th about a dozen times. It accelerated extremely slow so you need a LOT of open road. I got a built trans from RPM so I don't know what the long term effect would have been.
Pro
Joined: May 2010
Posts: 624
Likes: 1
From: Northern NJ
I thought I heard Jay Leno in one of his videos talking about 6th gear being a real gear, not an overdrive gear. What am I missing?
Race Director
Joined: May 2005
Posts: 15,960
Likes: 21
From: West Norriton PA
St. Jude Donor '08
Banned Scam/Spammer
Joined: May 2007
Posts: 15,685
Likes: 1,330
From: Machineguns, because I don’t compromise
Just like ajg1915 said, he was referring to the ZR1 he was driving at the time of the video.... stating that GM "finally" put in a true 6 speed gearbox, where top speed is achieved in 6th gear.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Drifting
Joined: Apr 2003
Posts: 1,389
Likes: 10
From: Jacksonville FL
Another option is to have 5th and 6th replaced. I did this when I had mine upgraded. It now pulls hard to the top of 6th. I can use 6th in more situations, but my highway mileage has dropped.
Team Owner
Joined: Jun 2007
Posts: 30,770
Likes: 41
From: Down the Shore New Jersey, Elev.3 feet
St. Jude Donor '17
I use 6th to cruise down the Parkway to the shore. Usually going 75 mph. Any sped needed to pass someone goes back into 5th usually unless it's a slow pass.
Tech Contributor
Joined: Dec 2006
Posts: 10,962
Likes: 29
From: Van Buren Arkansas
Wounded Warrior Escort '11
My '99 has the stock Tremec in it and 6th is great for mpg but as stated above, probably won't do it for top speed. Now in my '07 with the MZ6 tranny, its ratio is lower as it was designed for the Z51 optioned cars which I do have. MPG sucks on the freeway but I think it might work for the top end max. No, I've never run it up there so I don't have a clue.
Drifting
Joined: Jan 2006
Posts: 1,372
Likes: 2
From: Ramona CA
The C6 Z51 tranny has different ratios in 5th and 6th gears. Put a C6 Z51 tranny in. 6th revs higher than a C5 6th gear.
Thread Starter
Pro
Joined: Jan 2010
Posts: 661
Likes: 2
From: Ca.
Our coupe is getting a s/c installed now, so when we get it back, I will test it out in 5th and 6th gear to see what it will do. The new clutch and pressure plate needs a break in period of 500 miles "per installer" so I will need to run it for awhile before the test.
