Transmission:Transmission, 8-speed automatic, electronically controlled with overdrive and tow/haul mode. Includes Cruise Grade Braking and Powertrain Grade Braking (Standard on models equipped with (L84) 5.3L EcoTec3 V8 engine or (L3B) 2.7L Turbo engine. Not available with (LM2) Duramax 3.0L Turbo-Diesel I6 engine.)