I have almost 7 years of trucking experience, but 6 of those 7 years were driving a truck with a standard (manual) transmission. I know how to use a jake brake on a truck with a standard transmission. I have been driving a truck with an automatic transmission for one year. Today I am getting a one year inspection on the truck, and the mechanic could tell I've not been using the jake brake. The mechanic says I am burning up the brakes way too fast by not using the jake brake.
When I first started driving the truck with an automatic transmission, I tried to use the jake brake two or three different times when I had a heavy load, and when I turned the jake brake on and applied the jake brake, the jake brake would slow the truck down, but the truck would automatically downshift to a lower gear (even though I did not want to downshift to a lower gear). Then the RPMs would be too high for the gear that the truck downshifted to, and I would have to brake even further just because the RPMs were too high. But my having to brake even further just to reduce the RPM's was problematic because I did not need to brake further just to keep the brakes cool enough. Then the jake brake would slow me down even further, and the truck would automatically downshift again, even though I did not want to downshift. Then my RPM's would be too high again, And I would have to brake even further again to get the RPM's down to the proper level. This was just a never-ending cycle. Next thing you know I am going 15 mph down a downgrade that I could safely go down at 40 mph with a jake brake on a standard transmission.
So how do you use the jake brake on an automatic transmission without having to go UNNECESSARILY slow due to the automatic transmission automatically downshifting (when you don't want to downshift) and then having to slow down even further because the RPM's are dangerously high for the new lower gear?
How do you use the jake brake on a truck with an automatic transmission?
Discussion in 'Experienced Truckers' Advice' started by expedite_it, Oct 22, 2020.
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And what exactly is "too high" of RPM?
Blue Zombie Trucker, God prefers Diesels, Dino soar and 3 others Thank this. -
alds, expedite_it, singlescrewshaker and 1 other person Thank this.
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Use a lower level of engine brake. You can also select a higher gear with automatics and they usually hold that gear if the engine brake isn't on the highest setting.
Would be helpful to know which year and model truck you have as different automatics have varied modes of operation.
Can't hurt to have whoever assigned you the truck teach you how to use it assuming the user manual is not available.tinytim, tscottme, expedite_it and 1 other person Thank this. -
Also, these new autos are synced up with the engine. I'd bet it won't downshift to an unsafe rpm..alds, Crude Truckin', Blue Zombie Trucker and 6 others Thank this. -
As I recall, the RPM's were around 2100 or 2200 when they were too high. On my tachometer, there is a red line at a certain point, and if the dial of the tachometer is in the red line, that means that the RPMs are excessive. As I recall, the dial of the tachometer was in the red line when I thought the RPM's were too high, but I don't definitely know that the dial was in the red line. It was a whole year ago.
When I get my truck out of the shop and start driving again, I will try using the jake brake the next time I have a heavy load and am going down a significant downgrade, and I will note how high the RPM's go.Last edited: Oct 22, 2020
singlescrewshaker Thanks this. -
singlescrewshaker Thanks this. -
If the RPM's are in the red line, isn't it safe to assume that the RPM's are excessively high?
It might be the case that I thought that the RPM's were too high when they were not too high.singlescrewshaker Thanks this. -
2200 rpm on the jake in an automatic is just about right.
If you start to slow too much just press the accelerator to disengage the jake. Release the accelerator to engage them again.
If you're doing it right you shouldnt even need to press brakes.singlescrewshaker, Jenn72 and expedite_it Thank this. -
On my 2020 cascadia when I first used the Jake brake my RPM's went up high too. If you tap on the foot brake it will reduce the RPM'S but your Jakes are still on when you let off the foot brake.
Once you learn how they work and set it correctly you won't need to touch your foot brake at all. When the Jake is set, it will let you go 5 over what is set. So remember to set it a little under going down to compensate for it.singlescrewshaker Thanks this.
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