We have the CTD with the 3.42s and we are pulling our 15.5K Fifth wheel just fine.
Went to the great lake Ontario back in September from eastern Connecticut and it pulled the trailer amazing.
Doing 65 easily up hills and not having to get on the gas at all just held steady.
from a dead stop she easily got up to speed and for the most part held steady at 12.3MPG.
Had a full water tank and full fishing gear for 4 adult guys for a week.
I thought I wasn't going to be happy with the gears but it works great so far. No complaints here