The Caterpillar 797 is a series of off-highway, ultra class, two-axle, mechanical powertrain haul trucks developed and manufactured in the United States by Caterpillar Inc. specifically for high-production mining and heavy construction applications worldwide. In production since 1998, the 797 series represents Caterpillar’s largest, highest capacity haul trucks. The current, third-generation model, the 797F, offers one of the largest haul truck payload capacities in the world, up to and has the highest payload capacity among mechanical drive haul trucks. Initial development In 1997, Caterpillar decided to begin the development of a payload capacity haul truck to meet the demand from large-scale mine operators wanting to reduce operating costs at mines using 80 to 90 short tons (73 to 82 t) per pass shovels. Engineers at Caterpillar's Mining & Construction Equipment Division in Decatur, Illinois, created a new design for the 797 using computer-aided design technology. This was the first time CAD tools had been used extensively to design a Caterpillar truck. 797 (1998–2002) Caterpillar first unveiled a completed 797 on September 29, 1998, at its assembly plant in Decatur, Illinois. The first two 797s produced were transported to Caterpillar's Arizona proving grounds for testing. In the second quarter of 1999, the third and fourth 797s produced were the first to be placed in service with a customer at the Bingham Canyon Mine in Utah. Caterpillar put 18 additional 797s into service with mine operators worldwide as production development units. Caterpillar began marketing the 797 in North America in 2000, with full worldwide marketing following in 2001. The first generation serial number prefix is 5YW. 797B (2002–2009) Caterpillar introduced the 797B in spring of 2002, replacing the first-generation 797. The 797B's increased payload capacity of is a increase over the first generation 797. Caterpillar increased the power output of the Cat 3524B EUI 24-cylinder diesel engine used in the 797 from net to net enabling the 797B to achieve a top speed when transporting a load, a increase over the first generation 797. The first 797B units entered service with customers in October 2002. 797F (2009–present) Caterpillar introduced the 797F to the public at MINExpo International in September, 2008. The 797F replaced its predecessor model, the 797B, when the 797F entered full production in late 2009. Prior to the introduction of the Caterpillar 797F and the Bucyrus MT6300AC at MINExpo International in September, 2008, the Liebherr T 282B, introduced in 2004,