Thanks for the advice Ian, you're absolutely right about the momentum. I had the same problem on our PNWX outing a few weeks back at one obstacle. Just as I was getting to the peak (which involved a high root, slick mud, rocks and trees everywhere), I let up on the go pedal.

One thing that happened this time though was that the clutch completely let go. At least, this is what I think happened due to the heavy, nasty unmistakable smell. On my first attempt I had the clutch all the way out, so the engine revved high, and the truck rolled back. Unnerving, to say the lesat. Anyways, new tires are the first thing on my list, but I'll be waiting for spring to buy them so no more rock gardens for me this year.