Have you had it in Low Range yet? If not, take it out for a spin around the neighborhood (again...not for an extended amount of time) without the trailer on it, put it in low and you'll be able to tell quickly she's not going to go very fast...nor should she. Driving it in low yourself will give you the best indication of when you should an shouldn't use it.
High range is very capable, so keep that in mind while towing and good luck with your trip!
What mountain range are you headed too?
