Eight-Speed For Corvette Gets An Early Announcement

At least they waited...

This paper, which has been pulled, was written by engineers at GM who worked on the project. The eight-speed, named 8L90, will feature shorter first gear ratio to improve acceleration, better fuel economy thanks to a greater spread of gear ratios, and the ability to handle up to 738 pound-feet of torque.

Three things...

(1) As far as performance and/or efficiency goes, only ratio spread and the number of gears matter. How tall or short the 1st gear is being relatively irrelevant since you can change the effective drive ratio by matching the transmission to an appropriate axle ratio.

(2) Being able to handle 738 ft-lbs of torque allows it to work with any "reasonable" rendition of the supercharged LT4. But a high torque loading typically means broad strong gears that equals weight and inferior efficiency. GM will need an 8L50 more than it needs an 8L90 -- it is the 2.0T and the 3.6 that needs the extra gears more, and it is these engines that drive volume.

(3) Another factor which goes unmentioned -- one which GM Hydramatics traditionally do not excel in -- is maximum shift speed. It helps to have a maximum shift speed of 7000 or 7500 rpm. This will especially be true of the lower torque rating 8-speed. For the mega torque transmission it is still good to be able to at least match the 6,600 rpm redline of the LT1. The current 6L90 for instance is limited to 6,200 rpm which robs the LSA and LS9 engines of some of their otherwise allowable rev range.