handling a downgrade

The guys that fly by you on down grades are morons. I don't care who you are you ride down it in a gear that is comfortable for you. I can't tell you what gear to be exactly in but if your coming down the down grade and the jake is doing all the work unless braking before a curve then your in the right gear. I drive a 10 usually 9 or 8 is good with the jake.

 

Every hill is different and requires different decent speed (gear). Some drivers become comfortable with a hill and know how they can make it down quickly based on their weight. They wrongly assume there will not be an incident on the way down requiring them to stop (they won't be able to).

Some don't care if they have to use their brakes on and off. If it's a serious grade (6+/-%) and more then 4 miles, I prefer to find a [jake] speed that will hold steady around 1,500 RPM without applying any air brakes until I can see the bottom and know it's less then a mile away. I will alternate jake mode from 3-1 heads as the grade changes to try and stay in the 1500 RPM range. If you're in the west and dealing with one of the serious western grades, don't take them lightly. Those going down fast may be light or empty or just stupid.

Until you know the particulars of a given decent, assume the grade will be as marked all the way down and constant and err on the side of caution. As you learn the hill you will find more optimal and maybe a faster decent speed (higher gear)

Just know that with jakes, there is no hill that can not be descended with no brakes at all if you go slow enough. even a 10% hill can be descended with jakes only and heavy.

Some hills out west have a nasty habit of providing reduced decent grades part of the way down giving a driver a false sense that they are out of the woods, then they go up a gear, then round a corner and see it drops off again, stepper then before and then they struggle to get slowed back down (as they should)

 

Remember this :
You can go to slow on a downhill a 1000 times,you can go to fast down that same hill only once.


Those others might be empty.

There is no standard formule to determine which gear you need.
There is your weight,% off the grade and distance to concider.
Ideal is to use no brakes.

Take it slow for now...............you will pick up speed in time as you get to know your truck better.

 

For that i refer you to the manual off your truck.
It should have that info.

 

I don't like to rev over about 1,700 on any cummins or detroit on a down grade. But long term, like to stay under 1600. The jake will work better at higher rpms, up to a point then will become less effective as rpms continue to increase past that "sweet spot". Seems every engine's sweet spot rpm is a little different in terms of optimal engine brake holding power.

 

In the right gear I've taken 9% grades without ever touching the brakes. Like the other guy said, those guys flying by are morons and would not be able to stop in an emergency.

 

Important points per downgrades:

1. When you have a heavy load is when your brakes can be overworked, overheated, and lose their ability to stop your truck. That is not likely with a light load or empty trailer. If you ever see smoke coming from your wheels, your brakes are obviously being overheated. (Hello, Donner Pass!) If you see much smoke off your wheels, either gear down and use the brakes less to let them cool, or get off the road and let them cool. Don't ever let the brakes get too hot or it will be too late and you will have a fire that might burn up the whole trailer and tractor. Use the mirrors to know if any smoke starts coming out. A little bit of smoke now and then is probably all right, but some drivers might disagree with me on that one. Until you get into the western part of the United States, you don't know what a real downgrade is.

2. Getting the RPMs higher, like up to around 1900, will make your jakes work much more effectively. Low RPMs such as 1500 aren't nearly as effective for the jakes.

3. Jakes are not meant to be used on slippery roads like ice because only the drives are slowing down and the other tires can lose traction and you can lose control of the truck. Some people use jakes all the time: probably not smart. But if you combine braking, which works on all tires, with jake braking, you might get away with somewhat slippery road like rain. If I had a heavy load on a slippery downgrade, I might use the jake at the lowest setting and mostly use the regular brakes. If you cannot use the jakes much or at all, you might need to go down an icy grade at literally 10 or 15 mph to be truly safe. Use flashers, of course.

4. How to choose the correct gear to be in: you keep going into lower and lower gears until your jake is doing most of the slowing of your truck and you don't need to use the regular brakes very much. That is how you choose which gear. There is no pat answer. The heavier your load is, and the steeper your grade is, the lower your gear will be, and the slower you will be going.

5. As other drivers have said, if you choose slow vs. fast, your chance of a catastrophic accident goes way down. Be patient going down hills. What if there is a parking lot (stopped traffic) at the bottom? Be safe.