Spied: 2010 GMC Sierra Heavy Duty

It seems our spies are getting closer to the final grille for the 2010 GMC Sierra HD pickup. Seen in this photo (top), the four bar setup has been revised to a three bar theme with a squat honeycombed pattern running the length of each bar.

Making no effort to disguise itself, the 2010 GMC Sierra 2500 test mule in this picture is running with GM's updated 6.6-liter Duramax diesel V-8 under its hood. The Duramax is expected to receive a significant increase in horsepower and torque next year (well over 700 pounds-feet of torque, sources tell us) as well as meeting full Tier 2 Bin 5 federal emissions rules - the toughest clean diesel standard in the world.

The Sierra's grille has been toned down (from four horizontal bars to three) and its front bumper has a larger inlet for the Allison transmission's oil cooler, like the 2010 Chevrolet Silverado 2500 we recently spied.

If you look closely at shots of the Sierra's right front passenger side you can see what we believe is a temporarily placed urea tank strapped to the frame (directly under the front passenger door) for testing the new diesel emissions system. Urea fluid is injected into the exhaust stream to reduce nitrogen oxide levels. When it reaches production, the urea tank will have to be refilled periodically during routine maintenance and service.