Driving down steep grades in icy conditions

I've been thinking about this thread, especially @Toomanybikes suggestion that simply advising folks that using Jakes on a slick downhill might lead newer drivers into trouble. The video in the OP is a really good example of how to do it and the driver talks through much of it really well. Allow me to discuss some of what I have learned.

Let's take a typical scenario faced by OTR drivers: running I-70 west of Denver in the winter when chains AREN'T required. The roads could be bone dry or there could be slick patches, but a common problem will be the lenticular cloud sitting on the pass above the Eisenhower Tunnel. For several miles on either side of the pass you are in a blizzard and the snow plows either can't keep up or the storm was so sudden they haven't started yet.

Coming out of the tunnel you start your descent without chains in really slick conditions. You need to control your speed, but without using Jakes you are faced with miles of 6%+ grade to get down without overheating your brakes.

Jakes hold you back by basically turning your cylinders into air compressors:

How An Engine Brake Works

If you have an eight cylinder engine and three different Jake settings (Low, Medium, and High) then in Low two out of eight cylinders will be holding you back, Medium will have 4/8, and High will have 6/8. It's impossible to have all the cylinders run a Jake, because that would stall the engine.

The higher your rpm's the more powerful the holding power of the Jake. The Jake is designed to cancel itself if your rpm's get down to 800 so it won't stall the engine.

Now let's apply that to descending Eisenhower in a blizzard. I start in a gear at about 800-900 rpm's, where the Jake has the very least amount of holding power. I select Low setting. This applies the least amount of holding power to the drive tires. As rpm's increase past 1200 that holding power increases and I experiment with Medium with light (5 psi brake pressure) or even High IF I don't feel any loss of traction.

The moment I feel even the slightest loss of traction I will immediately cancel the Jake and get on the service brakes lightly, maybe even upshift as needed. This means you temporarily will pick up speed. Control that speed with light service brakes and get back below 1000 rpm's and try again in the new gear with light Jake setting.

Obviously in these kind of conditions you want to be going slower than dry conditions. The goal is to find the gear that allows you to modulate between Low and Medium Jake with light snub braking or light continuous braking. Be prepared to upshift and coast for a couple of seconds without jakes if you feel yourself starting to slide and apply light service brakes to bring the speed back down. Coasting is your friend, it helps eliminate a slide.

The important difference between using Jakes in dry versus slick conditions is speed of descent and setting. You come down slower in slick conditions and at lower Jake settings.