The tranny and rear end in this truck are proven, off-the-shelf units--especially the tranny--the same Aisin unit used in the Ram 3500. The Cummins 5.0 V8 has already been used in some commercial applications, so this engine has some history in the realworld. You can bet Nissan looked closely at this data before committing to this engine. This drivetrain looks like a winner.
As I've said in the past, for those expecting this truck to have an MSRP less than a 3/4 ton diesel just because it has less payload/tow capacity will be sadly disappointed.
The most popular (best selling) 1/2-ton trucks AND 3/4 to 1-ton trucks (diesels included) ALL have MSRP's from $45k-$55k. IMO, it's a given the Nissan Titan Diesel will also have a "competitive" MSRP in the $45k-$55k range.
IMO, 1) the Cummins engine, 2) use of a proven (heavy-duty) off-the-shelf tranny/differential, 3) the estimated 16/22 EPA MPG numbers, and 4) Nissan's generally good reputation, will make a it a very tough competitor---pulling sales away from both the 1/2 and 3/4 ton truck segment.