2006 Explorer 4.6 v8 has no power to tow up mountains?

jimh425 wrote:
Thanks for all of the comments so far. It helps me understand what's going on.

It's a pretty simple matter really.
You didn't have an engine big enough to pull up a mountain grade COMFORTABLY. Meaning YOU weren't comfortable; the engine likely was doing just fine. If you have a "tow package" the transmission should be fine too.

And looking at the picture, wind resistance might be as big a factor as sheer weight.