I just did something similar this last week. Put it in 4hi to roam around the driveway and forgot. Rolled about 10 miles averaging about 55-60. I haven't noticed anything wrong with mine yet.
2010 XLT Tuxedo Black Super Cab, 4x4, 5.4L, Westin Black Side Steps, Vortex Spray in bed liner, Firestone air compressor & rear air bags, Hornblaster four horn package
Towing: 2007 Grand Surveyor GS280, 31' travel trailer