billinstuart

with 3.73 rear gears, you tow in a lower gear, like 3rd in a 4speed. This leaves a true overdrive for when you aren't towing. Often 4th or top gear is overdriven through a planetary drive, where 3rd is direct..1:1. Depends on the tranny.

weatherman

I have a 2006 1500 Silverado Vortec Max with the 6.0 and the 4.13 rear axle, which is the combo required for maximum trailer towing. My truck is a 4x4 crew cab, short bed, with the 4-speed auto. It is rated to tow 10,500 lbs., and really does tow well. I've not had a problem at highway speeds. We also have a 2007 Denali XL with the 6.2 liter, All-wheel Drive, and the 6-speed auto. That sucker is the BOMB to tow. I really love the 6-speed auto, and the Denali really is a nice vehicle. The auto-leveling rear suspension makes the ride nice loaded or empty.