The exact history of these two units is uncertain but one is thought to have been used by Transportes Especiales Grau, also of Barcelona following its service with Transportes Modernos. Prior to the acquisition of the Hayes, Transportes Modernos had used a variety of heavy tractors, including some unusual 6x6 DC-Series Autocars.

These two Hayes W-HDX 6x6 tractors were shipped from Vancouver via the port of Bilbao and were imported into Spain in the spring of 1976. Specifications were almost identical to the earlier units except that Clark axles were fitted rather than Mack. It is thought likely that these units would have been built by Hayes whilst the company was under Paccar ownership, Mack having sold the concern to a division of the Paccar group of companies in 1974.

One unit immediately entered service with Transportes Especiales Arbegui while the other was initially acquired by Transportes Grau. This unit (seen in these photos as the “push unit” working at the rear) later served in the Transportes Modernos fleet before being finally acquired by Transportes Arbegui in 1989.

Arbegui refurbished both of these tractors in the 1990s and they often work as a team hauling loads for the Nuclear Power Authority aboard the company’s Trabosa modular trailer.

This particular move involved the transportation of a 340-tonne vessel from Hospitalet d’Enfant near Barcelona to Asco and gross weight of the tractors (complete with ballast blocks for greater traction) trailer and load was 580-tonnes. Although only 57-km, the haul required three days to complete because of very steep grades, a detour to avoid a weak bridge crossing a tributary to the river Ebro and the need to cross a main railway line without disrupting the rail service.