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 (LR4) Engine, Vortec 4800 V8 SFI or (LQ4) Engine, Vortec 6000 V8 SFI. Not available with (LLY) Engine, Duramax 6600 Turbo Diesel V8. Reference the Engine/Axle page for availability.)