General Motors' latest workhorses are all-new for 2009. The Chevrolet Express and GMC Savana 4500 commercial cutaway vans are engineered to support the needs of three primary functions -- school buses, shuttle buses and ambulances.

The Express/Savana 4500's is capable of supporting 14,200-pound GVW with a payload rating of 9100 pounds on the new and stronger chassis. The chassis was engineered to minimize mass and strengthen the chassis. The reinforced frame assembly and other necessities (such as new rear axle with reinforced housing, gears, and axle tubes, upgraded rear spring hanger bolt attachments and leaf spring shackle assembly, high-capacity rear spring assembly, upgraded front ball joint material, revised front and rear shock tuning, and rear stabilizer bar) were modified for the same reason. Brackets also were added to the upper and lower sections of the frame's side rail bulkheads for more strength as well.

The Chevy Express and Savana 4500 chassis offers to handle approximately 2500 pounds in GVCW and up to a 20,000-pound GCWR, making it ideal for exceptional towing, RV, and school bus functionally. And GM will be the only OE to offer an emissions compliant V-8 turbodiesel in the segment as well.

The new Express/Savana 4500 will be offered with a gas V-8 and 6.6-liter Duramax turbodiesel V-8. The Duramax 6.6-liter features new enhancements that promise to deliver less emissions using cleaner, federally mandated Ultra Low Sulfur diesel fuel. The Duramax 6.6-liter V-8 is rated at 250 horsepower with 460 lb-ft of torque. The Duramax engine uses a new electronic variable cooling fan that delivers better cooling and quieter operation.

The Vortec 6.0-liter gas engine features variable valve timing for enhanced performance and optimized fuel economy that produces 323 horsepower. The Vortec 6.0-liter is based on GM's Gen IV small-block V-8 engine family that features a deep-skirt cylinder block and cross-bolted six-bolt main bearing caps.

Both engines are available with the HD 4L85E four-speed automatic transmission designed for the heavy-duty use. It features a brazed torque converter turbine, induction-hardened turbine shaft, five-pinion reaction and output gear carriers, and an improved overrun roller clutch. The 2009 4500 also includes General Motors' Oil Life System that tells you when to change oil and filter based on engine operating conditions.

Most of the 4500 chassis include a new 57-gallon rear-mounted fuel tank that tank is positioned lower on the chassis and designed with input from upfitters. The school-bus 4500 applications are the only chassis that won't have this feature. The 57-gallon tank's fuel sender and all the fuel lines are upgraded to meet B5 biodiesel performance requirements.

Each model comes with GM's five-year, 100,000-mile limited powertrain warranty.