Original post by: Colin Allan ,
The difference is the engine family. The Detriot diesel corp. class 8 engine was usually a "series 60" starting back in the early 90's they were 11.1L and more commonly 12.7L and then there were different generations of refinement ie. ddec I,II, III, IV up to I believe 2003 where they switched over from 12.7 to 14L to meet BHP ratings due to EGR also I think they also switched to ddec V with was the last update in development, they carried that version of engine through 2008 where the "DD" engines came into play. The DD13 is 13L and the DD15 is a 15L and there is a DD16 also....Some useless trivia for you there was pre EGR 14L starting in 2000 they came in at 575BHP/1850TQ and 550BHP/1850TQ they are rare I own one factory installed, but I would advise against buying one because parts like Turbos and engine specific parts and VERY hard to get.