That happened to me last year on Chinamans - well not EXACTLY that...
I was going along fine, until we hit the Whale-tail, and I was POWERING OUT.
I thought "wait a minute! Since I put the 4.24:1 low range gears in, I have NEVER powered out, even at Moab"...
Sure enough, I was in 4-HI... Sheesh!
Sold the Gnewt.
Bought a boat.