The 6L90 transmission is a six-speed automatic that was introduced in the Chevy Silverado and GMC Sierra in 2007. It was designed to replace the older four-speed automatics that were becoming less capable of handling modern engines' increasing power and torque output. The 6L90 is a heavy-duty transmission that is built to handle large loads and powerful engines. It is important to note that the type and amount of fluid needed will vary depending on the specific model of your truck. However, most Silverados will generally require between 10.5 and 12.4 quarts (with a cooler) of transmission fluid.