I have some recent experience with this. I might have even posted here before that I did the Mount Washington descent last year and 1st gear engine braking did not hold me whatsoever to the point my brakes were smoking and I had to pull over. I was in high range last year. I did the same drive this year, and this time I did it in low range. I had no issue this year running in 1st and 2nd low range, even on the steepest portions (~18% grade). I rarely had to use my brakes down the entire hill, and was going between 5-15mph throughout at around 3000-5000rpm. 1st gear will absolutely slow you down no problem to a near crawl on the steepest descent, but you won't be going very fast at all as you might imagine. Fortunately for me, I was the last vehicle down the mountain after they closed the way so I didn't have to worry about anyone behind me.
Regarding DAC - I think you need to be in high range for that so even though it is better than you in terms of braking efficiency, you would still end up with smoking brakes and need to pull over. When your in low range, I believe DAC changes to crawl control.
Regarding DAC - I think you need to be in high range for that so even though it is better than you in terms of braking efficiency, you would still end up with smoking brakes and need to pull over. When your in low range, I believe DAC changes to crawl control.
