[hatesmith]

I don't know if this helps, but I live in West Virginia (the Mountain State), and at the slightest hint of a hill when the cruise is on, my car (pretty much the same as yours) immediately goes to fourth, then to third. If you live in a more mountainous region, what you are experiencing may be normal, but if you live in a "normal*" area, you may want to have your **** looked at.

*not a major North American mountain range.