[AAIIIC]

is one able to swap the trans for one with taller 6th gear. Like maybe a .5 overdrive? As my 1990 corvette Zr-1 corvette has. 1400 rpm at 60 mph.

According to Wikipedia, there have been a number of T56 applications that used a 0.50:1 6th gear - Borg-Warner T-56 transmission - Wikipedia. Do your research on the differences (bellhousing, mounting, shifter location and type, etc) between T56s from different cars, then figure out what you might be able to swap from to get the gearing you want. Or talk to one of the various shops that specialize in T56s and see if it might be more economical to just swap in the 6th gear you want.

 

[Kaline]

There is not another TREMEC transmission which swaps into a 2nd Gen CTS-V due to its unique tail housing.

The “MG9” transmission used in the 2nd Gen CTS-V uses a close ratio gear set of 2.66/1.78/1.30/1.00/0.79/0.63

This is similar to the “MN6” trans used in the base 5th Gen Corvette (non-Z06) which has close ratio 1-4 and wide ratio 5-6 of 2.66/1.78/1.30/1.00/0.74/0.50

A competent transmission shop (such as Liberty’s Gears or RPM) should be able to rebuild an MG9 transmission with taller 5 & 6 gears from the MN6 if a customer desired.

 

[albert.marcoss]

Yesterday I drove my C5 to work and realized just how nice it was to have a tall 6th gear. Cruising down the highway at 70 MPH is a mere 1500 RPM. In the -V, it's somewhere around 2300. While I can't blame the short gearing for my appalling fuel economy in the -V (12.7 MPG), I can't help but think that it would improve the situation.... The car has more than enough power to handle a more leisurely RPM during freeway cruising, don't you think?
Nox Vidmate VLC
Anybody else wishing they would have made 6th gear a little taller?

I think 80mph at 2000rpms would be ideal.