Cummins had an exclusive deal with RAM as a supplier, that changed in 2013 (according to Nissan) when they started planning for the smaller engine in their Titan pickup. Now as to the why RAM couldn’t have gotten the same one, either licensing prohibited it or RAM thought it too big for either the front suspension or perhaps CAFE standards.
Heres an Autoblog.com article excerpt from Sept 27, 2013:
Nissan Titan's upcoming Cummins diesel originally meant for Ram
DAMON LOWNEY
Sep 27th 2013 at 9:13AM
(Begin quote)
“The
Cummins 5.0-liter turbocharged
diesel V8 that
Ram initially planned to use in its pickup trucks instead will find its way into the
2015 Nissan Titan as an option,
Automobile reports. It will be the first time a non-Ram pickup truck will be available with a
Cummins diesel engine.
The move comes after
Chrysler decided to use a 3.0-liter V6 EcoDiesel engine designed by VM Motori (which is partially owned by
Fiat) due to
fuel economy concerns with the Cummins engine.
Chrysler wanted its
2014 Ram 1500 trucks to achieve at least 26 miles per gallon. "Our simulations were showing 23 to 24 mpg [for the 5.0-liter engine]," says Mike Cairns, head of engineering at Ram.
Nissan had plans in 2008 to team with Cummins for a diesel engine for its
Titan, when there were also plans for the second-generation Titan to share its platform with the
Dodge Ram 1500, according to
Automotive News, but that didn't pan out after Chrysler's bankruptcy in 2009.
Now that the dust is settling, let's put the pieces together. The 2014
Ram 1500 will get the EcoDiesel V6 as an option, making 240 horsepower and 420 pound-feet of torque; heavy-duty Rams can be equipped with the Cummins 6.7-liter diesel I6, which makes 350-385 hp and 660-850 lb-ft depending on the state of tune; and the
2015 Nissan Titan, a light-duty pick-up, will get the Cummins 5.0-liter V8 as an option, which makes roughly 300 hp and 500 lb-ft.” End of quoted article