I used to do a lot of rock crawling in my Bronco II, back when I was hang gliding 25+ years ago. Took my son over Black Bear Pass then - had him run the video camera so he would be occupied and not so aware of the danger. It is VERY STEEP, off camber, loose rock / shale, very narrow with 2,000ft cliffs. It is so steep the tires slide and little rock mounds pile up in front of the tires as they slide. You have to release the brake, hop over the mounds and get back on the brake immediately before building speed - all while engine braking in granny gear, and get her stopped before you arrive at the hairpin switchback immediately ahead. This is with the tires on the edge of the cliff with gravel from washes making the truck lunge towards the abyss. White-knuckler for sure - for experienced, cool composure drivers only.
In the video linked above, at the start the driver has already gone past the hairiest part described above. This is the west face of the box canyon, the highest road section shown in the book picture below. The scary steep narrowest part is in the corner of the box, the face is to the SW above this section.
We have also done Mosquito Pass, Imogene, Cinnamon, Engineer and many others in the Colorado Pass Book. Love the San Juan Mountains for these adventures. Got a lot of hairy stories but I'll leave them for another time. Here's the CPB page on Black Bear. Read especially the highlighted parts.
