Hello, I am new to this forum and work for a construction/ excavating company and the majority of our trucks are Mack tandems and tri-axles. We currently have 4 Mack Granite Dump Trucks (2004-2007) that have given us a lot of frustration. They have a severe loss of power when traveling up an incline (loaded and empty). They have the 370-410 engine. We have taken them to the dealership and other service departments and they have been unable to find the problem. Has anyone else experienced this same issue and could possibly offer some insight? Would be much appreciated. Thanks!