Double edged sword of 8 speed 8l90 transmission in 2015 Corvette C7 Stingray and C7 Z06

Like with everything else, so called upgrade of Stingray's automatic transmission is a matter of give and take or, in other words, a matter of compromise.

As it is, the current 6 speed transmission has been modified to make the car faster in straight line acceleration, aiming specifically at quarter mile run:  smaller torque converter (lower rotational inertia) and higher stall speed.  Even though the gears and final drive are a carry over from C6 generation, the modifications proved to be effective at both drag strip and in 0-60 testing.  The numbers are higher, at expense of increased temperatures and decreased longevity of the transmission, should anyone attempt to repeat the results on continuous basis.

However, the new Corvette continues to be advertised as a fuel efficient sports car and the current gears, their count and ratios interfere with this claim.  Thus, for 2015 model year, the new slush box gains two additional gears, in an attempt to cure this problem.    As it happened, +Tadge Juechter keeps bragging about new transmission being capable of shifting faster than the old one?  Is this really the case? 

As a matter of fact, this may not be a case at all and only the quarter mile runs of the  Stingray equipped with the new transmission will be able to shed sufficient light to resolve this mystery.

Why?  For a very simple reason, the new 8 speed transmission gearing is set up in a way that allows for 0-60 run to be accomplished right before red line in second gear, with the max speed in 2nd gear being either 65 mph (Z51) or 70 mph (non Z51).  This is a significant change from the current 6 speed transmission and the corresponding speeds being 82 and 87 mph.  

With the new transmission, the 0-60 time will be achieved at the top of the max torque and right before it drops abruptly as it approaches the 6500 rpm redline.  This is actually a very clever marketing attempt by Juechter to create an illusion of the 2015 Corvette and ultimately the new Z06 being faster.

However, there is a problem here, with regards to quarter mile runs.  Unlike the current 6 speed transmission, the 8 speed version will need the fifth gear to achieve the quarter mile trap speed.  Currently, the quarter mile runs are completed in THIRD gear.  The difference of two extra shifts will truly disclose the actual improvement in the transmission and its alleged superiority over a dual clutch counterpart that is a norm in the rest of the high performance automotive world.

If indeed, the quarter mile time will improve for 2015 Stingray and then again for the upcoming Z06, then Juechter and the rest of his team will indeed have a valid claim but.... this has to be demonstrated by the quarter mile times, not by 0-60 times alone since the new transmission achieves this part by new gears instead of improved shift speeds.

Now, knowing Juechter and +General Motors marketing team, there may be once again, more incomplete and misleading performance figures for 2015, in case the new transmission does not deliver on the claims already made.

Will there be a new final drive ratio:  this part is possible but unlikely, considering the maximum speeds achieved with the current ratios.