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

If you can't pull a drift boat over Snoqualmie Pass you do not have much of a tow vehicle. I believe towing at 5,000 rpms is a mistake.

Some people seem to do fine with that engine. I would suggest trying a lower gear and going slower.

My grandfather used to talk about driving over Snoqualmie when it was dirt and there were 38 stream crossings on the West Side.