The 2007 model year offered both engines
I ordered my Dodge with the 6.7 back in March of 2007 and at that time no dealer in this area had any 6.7 trucks all they had was 5.9 trucks on the lot and several months later they got them. When I ordered my truck only the 6.7 was an option for special ordering
The cutoff date was supposed to be January 1st, but I would guess it was later in January or maybe even February before they stopped making the 5.9. I testdrove a 6.7 in Pinedale in mid-late March, was the first one they got and they had gotten it the night before. I likely woulda traded if I hadnt just got my Smarty the day before.
The feds didn’t phase the new emission rules in with a model year that did it at a particular production day. In this case all diesels made after January 1st 2007 had to meet the new emission rules. There for Dodge as well as GM and Ford switched production to their newer engines on or just before January 1st. So if you see a 2007 and it was built before this date it would have the 5.9, all built after have the 6.7. For this reason the 6.7s are sometimes referred to as a 2007.5 model year.
You are partially correct. The Feds did mandate a 1 January, 2007 effective date for tier III emission for diesel engines. What this means is any engine built in 2006 could still be sold in a new trucks built in 2007 but if the engine was built in 2007 it had to meet the tier III emissions rules. Most engine builders built a stock pile of engines that would allow them to be sold through part of the model year of 07.
Cummins choose to meet Tier IV emission rules instead of Tier III and not have to introduce another engine model in 2010. This was to save R and D cost along with the availability of marketing an engine that was Tier IV emission compliant before the competition.
Also, weren't there two versions of the 5.9 available in 2007? The H.O. and regular flavors. If I remember right, the H.O. 24 valve Cummins could only be had with a 6 speed manual, and I think the regular 24 valve Cummins could be had with an auto or 5 speed manual. I know a guy who has a 5 speed manual.
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