GM isn’t making a lot of changes to the full size pick-ups next year. One change is the new 4.5L Duramax being put in the Silverado/Sierra 1500. Which is going to be very cool, and should sell very well. This might not come out until later in 2009 and it might be considered a 2010. Test mules of a 1500 Diesel have already been spotted driving around so I think they are closer to the launch then many people think. By the way this 4.5L Duramax is producing around 310 horsepower and 520lb-ft of torque.
The six-speed automatic transmissions (6L80) will be a option for the 5.3L, 6.0L, and 6.2L V-8 engines. GM says extra gears means better MPG, Lower RPMs when on highway and around town means better fuel efficiency. That’s a plus, but I think the six speed should be a standard feature. Interesting fact about this Auto trans, is that it’s the same one used in the Corvette. The 2500 and 3500 Silverado/Sierra, are mostly unchanged for 2009 most of the additions are small. You still have the Monster 6.6L Duramax Turbo Diesel under the hood, producing 365 Horsepower. 660lb-ft of torque. Also the same six speed Allison automatic and ZF six-speed manual transmission.
So at the end of the day, The GMT 900 and GMT 910 Platforms are still pretty new, they just came out in 2007, we probably won’t see a all new Silverado/Sierra until around 2012. If your interested for more information, I’m going to leave you with a link for Motor Trend’s first look at the 2009 Chevy Silverado.