So I towed my 29ft, 7000lb (loaded) travel trailer over 3400 miles the last two weeks. My truck is a 2wd longhorn with the 3.55 rear axle. This was the first trip with the new trailer and I couldn't ask for better performance from the ecodiesel. I traveled from Phoenix, AZ to San Antonio, TX up through Albuquerque, NM, onto Durango, CO and then back down to Phoenix. I had a wide variety of terrain, altitude and temperatures ranging from 110 degrees to 56 degrees. The ecodiesel never had an issue pulling anywhere. The only time I did experience any notable straining of the engine was on a steep grade out of Payson, AZ where it started to get hot while trying to maintain 55mph up the grade. I had to slow down to about 45mph for the engine to cool down.
Maintaining 70mph on the interstate was never an issue. I did run at 75mph for a bit, but fuel economy suffered and dropped into the 10's. Also noted the trailer would get squirrelly at those speeds. 65mph seemed to be the optimal cruise speed. The turbo diesel didn't seem to suffer from a loss of power at altitude either, so it appears Chrysler did a good job of adjusting the boost pressure to compensate for air density. Running without the trailer, I drove the truck through several 10k+ feet mountain passes without a single issue. Overall I averaged 13.5mpg towing, which was about what I expected it would do given the size and weight of the trailer. I normally get 25-27mpg with no load. Pulling up grades with the trailer was no issue, and truck braking coming down steep grades was also good.
I did add a set of Airlift airbags prior to the trip. It made a huge positive difference in the ride of the truck and leveled the rear of the truck nicely with the trailer attached with only about 20psi of air. It also corrected an up and down oscillation I had noticed when I first pulled the trailer home.
My only complaint would be to have better manual control over the transmission gear selection. The truck would often stay in a lower gear longer than I wanted to and would not allow me to upshift. It rarely shifted to 8th and most often stayed in 6th or 7th gear. This is where the 3.90 gears would have been better and may have returned slightly better fuel economy.
Overall I was very impressed and love love love my Longhorn Ecodiesel.