Proper use of jake brake

Indeed, to clarify When you say air brake you are not talking about engine braking at all. I understand what you are trying to say but when talking about engine braking, jake braking is well understood by any trucker. Even though the actual mechanisms vary the result is the same, Using the engine's power to hold back a semi truck downgrade.

Service braking downgrade in a truck without a jake brake takes one of two forms. Snub braking or steady application of a light amount. Both have it's plus and minuses. There is also the trolley (Johnson Bar etc) for just the trailer tandem braking but not related to this topic of engine braking.

The goal is not a particular speed. In fact 68 is rather fast or too fast actually. Ignoring speed for the moment, the best goal for a 18 wheeler downgrade on engine braking is to have her in a gear that provides a sufficient braking to hold her at one speed (More or less) all the way down without touching the service brakes at all. Keeping the brakes cold and ready for use if something came up that is of emergency nature and you have need of them. that is the beauty of engine braking. You can come down 5 mph or 50 mph or even 500 mph as long your rig is in balance against the pull of gravity downhill and does not gain speed or fight you by slowing down too much. (She will nose down or buck etc)

Remember in a downgrade in the older trucks you come down in the gear you came up in with some exceptions. And you can always come down too fast once. (You will be killed, maimed or killing or maiming up to many others) A third thought is that you maintain power to the drives always. It works both ways in speeding up and in engine braking. Staying in gear down grade without shifting is a form of life saving safety. If you came out of gear, you better know to catch the next one up or down without missing it. If you botch it then you have a problem. A big problem. Shes gonna take off and run away.

Regarding trainers. You do what they tell you to do. Even if you have your own ideas. When you get your own truck you can experiment with your own ideas. With that said, in my day I just redline the hell out of the jake brake. PROVIDED that there is sufficient oil pressure, oil temperature and sufficient cooling temp at radiator AND a sufficient Pyrometer temp (Exhaust from engine at manifold) plus agreement from the transmission and axle temperatures. These date to the days where you had gauges for them to the right of your dash and as long all of them are in normal ranges and agree your rig is doing very well.

If you were coming down say Black Mountain on I-40 in NC, you see speed signs telling you to hold her no more than 30. In my last truck that meant she is in about 6th gear at around 1500 with jacobs engaged The RPM's will vary a little bit at 28 give or take a little As long she behaves in that gear you come all the way down black 6 miles without any problems or touching of service braking.

When I say don't touch service brakes does not mean to be afraid and NEVER touch them, once in a while you use them for a moment to keep the RPM in your shift range, most engines have a 400 RPM range between torque and horsepower RPM say 1250 to 1650. You can have a thousand gear transmission but as long you stay in this range your engine is happy coming up or coming down.

All engines have a redline. My Last one a 500+ detriot would accept a 2150 redline. And that provides me with a good set of options in steep mountains. If I was really careful on those I would come down in 1st gear at 3 mph and we will be here all day with 1000 more trucks waiting on me. (Not good) So I will find what hill I am on 5%, 7%, 9%, 10% 13% (Luray Gap VA) 15% 21 to 24% on up. 24 is my max. And there are several off road that are essentially vertical. You are at the bottom before you finsih playing with the jake brake switches.) One of my macks in bulk tanking would take a 2400 redline. That gives a lot of room for mountain work in those days such as it is where we ran.

I always do stage three in engine braking. Once in a while if its necessary to stay in a gear and stage three is just too much I'll let her have stage two or one briefly with the goal of establishing a balance for the tractor. But not too often.

I am also ignoring for the moment rain, snow, ice and so on. I am focused on the OP's issue with trainer and redlining. (As well as the speed of 68 and so on) These would be in a manual transmission OR a Automatic WITH a manual preset where you dictate or shift to a particular gear and stay in it all the way down just like a manual.

Your trainer has a certain way of driving the tractor trailer thats a given. Thats also why you probably are not running with that trainer anymore. There is no point in trying to worry about trainer's particular things about how to run a engine on a downhill. Hes already set in stone on how to run "His truck" and thats that. Hence my thinking when you get your own truck, you run it the way you think best.

Finally but not last. There are some grades where gravity becomes a advantage. About 18 miles down Donner from Reno you will find signs telling you to Let her drift. That means no braking, no engine braking and whatever gear you are in just leave it. If you were running Donner properly you are going to hit that section around no more than 32. your speed will vary with gravity for a little while between 25 and 32 as it did in that section with us loaded. Its a oppertunity to cool whatever brakes you used and a chance to cool your engine down and relax a minute before the rest of the downgrade gets to you.

Finally but not least, Ive said before that 68 seems fast. Somewhere on the downgrade all else being equal you are coming down in the gear you came up in at about or less than the speed you came up in. You can go downhill all day and never have a problem. Its when you go too fast and something comes along (And it will, you watch...) and you are going to find out what death or maiming is. If you are lucky you hit nothing and no one and have a good scare.

There are Escape ramps. ALWAYS keep in mind where they are at, how many you have passed. Once you get past the last ramp in control of your semi, usually the worst of the hill is at hand. DO NOT be afraid to commit to the ramp if shes running away and you cannot do anything to stop her. (Usually smoking, burning faded, and speedo climbing and so on...)

This is spring time. A chance to get acquainted, winter snow and ice and rains will be along soon enough.

 

If your in training just follow his instructions , at this point in your career just listen and learn . Once your done training and in your truck do as you please . You guys are the slowest trucks next to Prime trucks so you guys aren't gonna hurt these trucks at the speeds yall are governed. I had a terrible trainer but I knew if I just do my job and be quiet the experience would be over before I knew it . Good luck

 

All the time, esp in town and truck stops!

 

I'll keep it simple for the new guy. Once you get experience, you won't need this anyway.

Never go down a grade depending on your Jake to work.

Don't use it in slippery conditions.

Before every trip make sure all your brakes are in good condition and work like they should, particularly if you change trailers constantly.

Don't shift gears going downhill until you know what you're really doing.

Learn every aspect of your rig, how things work, and what the components are called.

Finally, you asking questions and seeking answers, tells me you're gonna do alright. Like @x1Heavy says, get going yer late...

 

Target 68 mph? Downhill?

 

Honestly, when I'm loaded heavy I keep my jakes in stage 3 all of the time, and run the transmission in manual mode as well and just paddle shift as needed. I prefer choosing my own gears and speed going up or down grades, and I never have to touch the brakes, and my RPM's never get above 2200.

 

If you’re using an auto you risk it shifting and being in a gear you really don’t want it in. You’re better off finding a gear it’s more stable in. If it’s slightly gaining speed it’s fine just tap the breaks abit to get her back but make sure it’s just slight braking and not moderate or heavy for the correction or you’ll hear your brakes up. If you find the gear slightly stronger then lower the jake setting from stage 3 to stage 2 or 1. Better to be on a gear too strong for the downgrade than too weak at least you have control. That’s the most important thing about being a truck driver ALWAYS HAVE CONTROL OF YOUR RIG.

 

Your right and your trainer is WRONG and I'm being nice

 

Did your trainer attend the cdl class right before you? What about the 3rd person in the truck? How do they use the engine brake?

 

I miss spoke. It’s not 1,2, or 3 cylinders, it’s 2,4, or 6. 1 head, 2 heads, or all 3.