Transmission:Transmission, 4-speed automatic, heavy-duty, electronically controlled with overdrive, tow/haul mode and internal transmission oil cooler (Required and standard when ordered with (LY2) Vortec 4.8L V8 SFI engine or (LY6) Vortec 6.0L V8 SFI engine. Not available with (LMM) Duramax 6.6L Turbo Diesel V8 engine. Reference the Engine/Axle page for availability.)