The HD variant was a heavy-duty light truck. It was a strengthened version of the Silverado/Sierra light-duty, and was available in the 1500HD, 2500HD, and 3500HD models. The 1500HD, introduced in 2000, offered a Vortec 6000 V8 with at 5200 rpm and of torque at 4000 rpm with a Hydra-Matic 4L80E four-speed automatic transmission. The 2500HD also offered the LB7 Duramax V8 with at 3100 rpm and of torque at 1800 rpm, the LLY Duramax V8 with 310 hp (231 kW) at 3000 rpm and 605 lb·ft (820 N·m) at 1600 rpm, and the LBZ Duramax V8 with 360 hp (268 kW) at 3200 rpm and 650 lb·ft (881 N·m) at 1600 rpm. Also available was the Vortec 8100 V8 with at 4200 rpm and of torque at 3200 rpm.