Ram dropped the Cummins in the 1/2 ton for the same reason they will soon drop it for a fiat engine in the HD trucks.
I live 25 miles from the Cummins Head Quarters. I have 2 neighbors who work there, one of which is the #3 man. They are all worried about the relationship with Ram. The are loosing tons of sales with Volvos purchase of Pacar shares and they fear the same with Fiat and Ram.
Think about it. Ram has no need for Cummins in say 3 years. They have proven the in-house Eco Diesel and can do the same in the HD line just like Ford breaking.off from IH