<P> The 2500HD has an available five - speed (six - speed for 2006 - 2007 models) Allison 1000 transmission with the Vortec 8100 and Duramax 6.6 . The Silverado 3500 offers the same engine / transmission features that the 2500HD does, however it is usually equipped with "dually" twin wheels at the rear and has a stronger suspension . The HD models are primarily used for towing and high - weight cargo . The Chevrolet Silverado 2500HD came in at #2 in a 2016 study by iSeeCars.com ranking the top 10 longest - lasting vehicles . The Silverado 2500HD had 5.7% of vehicles over 200,000 miles, according to the iSeeCars study . </P> <P> Towing capacity for the 1500HD is rated at 10,300 pounds (4,700 kg) and can haul 3,129 pounds (1,419 kg) in the bed depending on options . Towing capacity for the 2500HD is rated at 16,100 pounds (7,300 kg) with the gasoline 8.1 L V8 with 3.73: 1 rear and can haul 3,964 pounds (1,798 kg) in the bed depending on options . Towing capacity for the 3500HD is rated at 16,700 pounds (7,600 kg) and can haul 5,753 pounds (2,610 kg) in the bed depending on options . The addition of 4 wheel drive tends to reduce the towing and carrying capacity by 200 to 400 lb (181 kg), depending upon year and model . Other factors, such as options, can also affect these numbers . </P> <Table> <Tr> <Th> Model </Th> <Th> Year </Th> <Th> Engine </Th> <Th> Power </Th> <Th> Torque </Th> </Tr> <Tr> <Td> 1500 </Td> <Td> 1998--2003 </Td> <Td> 4.3 L Vortec 4300 V6 </Td> <Td> 200 hp (149 kW) @ 4600 RPM </Td> <Td> 260 lb ft (353 N m) @ 2800 RPM </Td> </Tr> <Tr> <Td> 2004--2006 </Td> <Td> 195 hp (145 kW) @ 4600 RPM </Td> <Td> 260 lb ft (353 N m) @ 2800 RPM </Td> </Tr> <Tr> <Td> 1999 </Td> <Td> 4.8 L Vortec 4800 V8 </Td> <Td> 255 hp (190 kW) @ 5200 RPM </Td> <Td> 285 lb ft (386 N m) @ 4000 RPM </Td> </Tr> <Tr> <Td> 2000 - 2003 </Td> <Td> 270 hp (201 kW) @ 5200 RPM </Td> <Td> 285 lb ft (386 N m) @ 4000 RPM </Td> </Tr> <Tr> <Td> 2004 - 2007 </Td> <Td> 285 hp (213 kW) @ 5200 RPM </Td> <Td> 295 lb ft (400 N m) @ 4000 RPM </Td> </Tr> <Tr> <Td> 1999 </Td> <Td> 5.3 L Vortec 5300 V8 </Td> <Td> 270 hp (201 kW) @ 5200 RPM </Td> <Td> 315 lb ft (427 N m) @ 4000 RPM </Td> </Tr> <Tr> <Td> 2000--2003 </Td> <Td> 285 hp (213 kW) @ 5200 RPM </Td> <Td> 325 lb ft (441 N m) @ 4000 RPM </Td> </Tr> <Tr> <Td> 2004--2007 </Td> <Td> 295 hp (220 kW) @ 5200 RPM </Td> <Td> 335 lb ft (454 N m) @ 4000 RPM </Td> </Tr> <Tr> <Td> 2005 - 2007 </Td> <Td> 310 hp (231 kW) @ 5200 RPM </Td> <Td> 335 lb - ft (454 N-m) @ 4000 RPM </Td> </Tr> <Tr> <Td> 1500HD / 2500HD / 3500HD </Td> <Td> 2000 - 2006 </Td> <Td> 6.0 L Vortec 6000 V8 </Td> <Td> 300 hp (224 kW) @ 4400 RPM </Td> <Td> 360 lb ft (488 N m) @ 4000 RPM </Td> </Tr> <Tr> <Td> 2000--2004 </Td> <Td> 8.1 L Vortec 8100 V8 </Td> <Td> 340 hp (254 kW) @ 4200 RPM </Td> <Td> 455 lb ft (617 N m) @ 3200 RPM </Td> </Tr> <Tr> <Td> 2004--2006 </Td> <Td> 330 hp (246 kW) @ 4200 RPM </Td> <Td> 450 lb ft (610 N m) @ 3200 RPM </Td> </Tr> <Tr> <Td> 2001--2002 w / LQY </Td> <Td> 270 hp (201 kW) @ 3600 RPM </Td> <Td> 400 lb ft (542 N m) @ 1600 RPM </Td> </Tr> <Tr> <Td> 2001--2002 w / LQQ </Td> <Td> 210 hp (157 kW) @ 3600 RPM </Td> <Td> 325 lb ft (441 N m) @ 1200 RPM </Td> </Tr> <Tr> <Td> 2002--2005 w / LRW </Td> <Td> 325 hp (242 kW) @ 4000 RPM </Td> <Td> 450 lb ft (610 N m) @ 2800 RPM </Td> </Tr> <Tr> <Td> 2002--2006 w / LRZ </Td> <Td> 295 hp (220 kW) @ 3600 RPM </Td> <Td> 440 lb ft (597 N m) @ 3200 RPM </Td> </Tr> <Tr> <Td> 2002--2006 w / LQR </Td> <Td> 225 hp (168 kW) @ 3600 RPM </Td> <Td> 350 lb ft (475 N m) @ 1200 RPM </Td> </Tr> <Tr> <Td> 2000--2004 </Td> <Td> 6.6 L Duramax (LB7 / LLY) V8 </Td> <Td> 300 hp (224 kW) @ 3100 RPM </Td> <Td> 520 lb ft (705 N m) @ 1800 RPM </Td> </Tr> <Tr> <Td> 2005 - 2006 w / MTX </Td> <Td> 300 hp (224 kW) @ 3000 RPM </Td> <Td> 520 lb ft (705 N m) @ 1800 RPM </Td> </Tr> <Tr> <Td> 2005 - 2006 w / ATX </Td> <Td> 310 hp (231 kW) @ 3000 RPM </Td> <Td> 605 lb ft (820 N m) @ 1600 RPM </Td> </Tr> <Tr> <Td> 2006 - 2007 </Td> <Td> 6.6 L Duramax (LBZ) V8 </Td> <Td> 360 hp (268 kW) @ 3200 RPM </Td> <Td> 650 lb ft (881 N m) @ 1600 RPM </Td> </Tr> <Tr> <Td> GMC Sierra C3 </Td> <Td> 2000 - 2001 </Td> <Td> 6.0 L Vortec 6000 V8 </Td> <Td> 325 hp (242 kW) @ 5000 RPM </Td> <Td> 370 lb ft (502 N m) @ 4000 RPM </Td> </Tr> <Tr> <Td> GMC Sierra Denali </Td> <Td> 2002--2004 </Td> </Tr> <Tr> <Td> 2004--2006 </Td> <Td> 6.0 L Vortec 6000 V8 </Td> <Td> 345 hp (257 kW) @ 5200 RPM </Td> <Td> 380 lb ft (515 N m) @ 4000 RPM </Td> </Tr> <Tr> <Td> Chevrolet Silverado SS </Td> <Td> 2002--2006 </Td> </Tr> <Tr> <Td> Chevrolet Silverado Vortec High Output </Td> <Td> 2003--2005 </Td> </Tr> <Tr> <Td> Chevrolet Silverado VortecMAX </Td> <Td> 2005 - 2006 </Td> </Tr> </Table> <Tr> <Th> Model </Th> <Th> Year </Th> <Th> Engine </Th> <Th> Power </Th> <Th> Torque </Th> </Tr>

What engine does a 2003 silverado ss have
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