No problems with it man. I pulled a 6x14 enclosed trailer (loaded with everything we own) from Oregon to Kentucky, over 8500ft in elevation in some spots. This was with my sport trac (4.0L auto) with 4.88s and 33" tires. If the transmission is shifting and hunting for gears a lot you should lock out overdrive. Most of my drive was in overdrive at 70mph or better.
It wouldn't hurt to run a bigger transmission cooler, or at least get a scan guage 2 to monitor transmission temps but it's probably not necessary either.
A trailer brake controller would be helpful if the trailer is equipped.
2006 F150 FX4 Super Crew - Bilstien 5100s leveled 2", 35" KM2s, 4.56 gears, Detroit locker, Eaton E-Locker, Traction Bars, AEM intake, Xcal 2
2010 VW Golf TDI 6MT