[obzidian]

6l80e gears:

First: 4.02
Second: 2.36
Third: 1.53
Fourth: 1.15
Fifth: 0.85
Sixth: 0.67

4l60e/4l65e gears:

First: 3.06
Second: 1.63
Third: 1.0
Fourth/OD: 0.7

Interesting, no true 1.0 gear, thour fourth is very, very close. With the drop in rear gear ratio with the new trans, it would seem as you are still achieving a lower cruise rpm per same mph with the new trans however, not enough to possible overheat the trans/drivetrain.

Also, went through a different set of gear/mph calculators. At 2000rpm, the est. mph in our current truck is about 72ish mph with an est. 35" tire, 4.11 rear and a fourth/od of .7. Now, at 2000rpm with the new setup, est. 35" tire, 3.73 rear with the sixth .67 ratio, that bumps it up to about 83mph.

So, your increase cruise speed at a given rpm, however, there MIGHT be a bit more strain on the trans though since it has more gears, it can more evenly spread the load instead of just 4 gears with the original 4l65e.

I really like the new powertrain of the 08. Finally GM is getting to something interesting... however, im not to sure on the interior, but i have to see one in person.