Launched in early 2003, the Silverado SS is a high-performance pickup truck built by Chevrolet. It is based on the 1500 Silverado Extended Cab with Fleetside Box and features upgrades in the drive train and both exterior and interior appearance. It was equipped standard with the 6.0 liter Vortec High-Output V8 rated at at 5200 rpm and of torque at 4000 rpm coupled to a 4L65E four-speed automatic transmission. This was the same engine used for the second generation Cadillac Escalade. Chevrolet and GMC advertised this engine as the Vortec High Output and later as the "VortecMAX", while Cadillac calls it the "HO 6000". The SS debuted in 2003 with a standard All Wheel Drive setup with a 4.10 final drive gear ratio and 4 wheel disc brakes. In 2005, in an attempt to increase sales, a 2-wheel drive version became available (the 2WD SS also lost its rear disc brakes in favor of drums, as did the rest of the 1/2-ton GMT800s). 2005 was also the first year the sunroof was available in the SS line up. In 2006, the AWD variant was dropped and the rear wheel drive was the only driveline layout available. In a further effort to reduce cost, buyers could also choose cloth interior and/or a bench seat. The Silverado SS also comes with the Z60 performance suspension and 20 inch aluminum wheels. All the SS trucks in both 2 wheel drive and AWD used the torsion bar style front suspension for better handling. SS themed trucks were only available from the factory in "Black Onyx", "Victory Red", and "Arrival Blue Metallic" from 2003 to 2004. In 2005, "Arrival Blue Metallic" was dropped from the color choices and replaced with "Silver Birch Metallic".