im looking at a 2004 duramax and i had a couple questions since im not familiar with the truck. i was wondering how strong the tranny is in the truck for modding? a buddy of mine has a CTD and has told me that the allison is not that mod friendly. to give you an idea of what mods id want to do- id be looking to do an intake, exhaust and a chip. anything else would be maybe a small lift, guages and tires. i drive 40 miles round trip a day, about 1900 miles a month. how reliable are they? whats your mpg in these things? how does it hold up to modding? around my way there is a duramax that runs low 14s and he has st acked chips and what not, but i dunno what else he has done. its either a duramax or a ctd in my future so im doing my homework on the duramax. powerjoke isnt getting my business.