Nissan and cummins.

Here's a link to the chassis page on the new Titan that shows the factory gooseneck hitch. It also shows a picture of the AAM rear axle, which looks an awful lot like the one I had on my 6.0 powered Chevy 2500HD. That was a 10.5" ring gear which seems plenty big. I agree, a 13" ring gear axle seems huge for a pickup.