A nice downgrade example

WB I-70, you're in the Eisenhower tunnel getting ready to drop off the hill.

Your speed is likely 45-55 mph, and you start letting speed bleed off as you see the "trucks 35 mph" signage. Slowing under very light throttle you downshift as needed, and exit the portal at about 20 mph, in your lowest high-range gear because you are at 80k lbs and facing a long 7% grade.

As you crest the hill, you set the cruise at 25 mph and engage the Jake. In this truck, that means the Jake stages engage at 28, 29, and 30 mph. You can now somewhat relax, keeping an eye on the rpm, engaging the engine fan on the steeper sections to provide that added touch of braking to keep the rpm below 2100, and if all goes well (no stupid people tricks) you will reach the bottom of the grade without having ever touched the brakes.

If you find that you are slowing to much, with the Jakes spending most of their time in stage 1 and 2, you can upshift one gear. In a 13/18, this raises your speed to about 35, and you'll likely have the fan on more often. Use great care going a gear higher in a 9/10, as this will jump your speed into the low 40's and most trucks will not have enough Jake to hold that speed, and require significant snub braking to maintain speed. Generally, if braking is required immediately after the upshift, it's best to continue braking until you can safely drop a gear.

The whole idea is to come down the hill with as little work load as possible, using the tools your truck offers to ease the descent. Why tarry away to gain at most a minute or two by snubbing your way down at a higher speed? Plus there is the benefit of completely cool brakes, which would have a measurable effect on how quickly you could stop if something happened in front of you.

 

Yeah, Rage. It always scared the dickens out me to see how guys ran down the hills back east. Anything ever happen in front of them and they'd be thoroughly screwed! We always joked back in the days when few trucks had Jakes that the Carolina boys were so scared of cabbage they would have their brakes hot before they ever got to the hill!